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... Numerical hydrological models offer universal descriptions of physical processes, more accurately reflect human activ-ities′ impacts, and provide a scientific basis for coupling with other physical processes (hydrothermal coupling, pollutant transport, vegetation dynamics), which has become an emerging and important direction in hydrological modeling in recent decades (Hu et al., 2007;Wang et al., 2008;Maxwell et al., 2014;Paniconi and Putti, 2015;Hrachowitz and Clark, 2017;Peel and McMahon, 2020;Shu L C et al., 2022;Figure 3 Schematic diagram of hydrological model classification (blue italicized text in the diagram represents representative models of each category. The models included are Xin'anjiang (Zhao and Wang, 1988), unit hydrograph (Sherman, 1932), HBV (Bergström, 1992), FLEX (Gharari et al., 2014), TOPMODEL (Beven and Kirkby, 1979), SWAT (Arnold et al., 1998), VIC (Liang et al., 1994), PRMS (Leavesley et al., 1983), WRF-Hydro (Gochis et al., 2018), WEP (Jia et al., 2001), GBHM (Yang et al., 1998), GSFlow (Markstrom et al., 2008), HEIFlow Zheng et al., 2020;Han et al., 2021), GSFLOW-SWMM (Tian et al., 2015), SWAT-MODFLOW (Park et al., 2019), FEFLOW-3D (Hu et al., 2020), SHUD (Shu et al., 2020), PIHM (Qu and Duffy, 2007), MIKE-SHE (Refsgaard and Storm, 1996), HMS (Yu et al., 1999(Yu et al., , 2006Yu, 2000), ParFlow (Kollet and Maxwell, 2006), PAWS (Shen and Phanikumar, 2010), HydroGeoSphere (Aquanty, 2013), CATHY (Bixio et al., 2002;Camporese et al., 2010)). Ntona et al., 2022). ...
... The WRF-Hydro system (Gochis et al., 2018) successfully coupled meteorological (WRF), land surface (NOAH), and hydrological (Hydro) models, simulating energy and water in the earth system, though its hydrological model component still has room for improvement. The HEIFLOW, GBEHM, and other models focus on the "watersoil-air-bio-human" coupling (Li et al., 2010;Yang et al., 2015;Tian et al., 2015Tian et al., , 2018Li et al., 2018) but also developed high-resolution ecohydrological products like precipitation, snow, evapotranspiration, soil moisture, and net primary productivity. These developments are extensively applied in critical process research, model development, and validation in watershed ecohydrology, revealing the complex hydrological cycle in the Heihe River Basin (Li et al., 2012(Li et al., , 2023. ...
Hydrological modeling, leveraging mathematical formulations to represent the hydrological cycle, is a pivotal tool in representing the spatiotemporal dynamics and distribution patterns inherent in hydrology. These models serve a dual purpose: they validate theoretical robustness and applicability via observational data and project future trends, thereby bridging the understanding and prediction of natural processes. In rapid advancements in computational methodologies and the continuous evolution of observational and experimental techniques, the development of numerical hydrological models based on physically-based surface-subsurface process coupling have accelerated. Anchored in micro-scale conservation principles and physical equations, these models employ numerical techniques to integrate surface and subsurface hydrodynamics, thus replicating the macro-scale hydrological responses of watersheds. Numerical hydrological models have emerged as a leading and predominant trend in hydrological modeling due to their explicit representation of physical processes, heightened by their spatiotemporal resolution and reliance on interdisciplinary integration. This article focuses on the theoretical foundation of surface-subsurface numerical hydrological models. It includes a comparative and analytical discussion of leading numerical hydrological models, encompassing model architecture, numerical solution strategies, spatial representation, and coupling algorithms. Additionally, this paper contrasts these models with traditional hydrological models, thereby delineating the relative merits, drawbacks, and future directions of numerical hydrological modeling.
... The Arabian Peninsula, encompassing countries such as Saudi Arabia, Yemen, Oman, the United Arab Emirates, Bahrain, Kuwait, and Qatar, is characterized by its arid climate and limited freshwater resources [3]. The significance of groundwater in these arid landscapes cannot be overstated, as it serves as a primary source of water for both domestic and agricultural needs [4]. With limited surface water features such as rivers and reservoirs, the Arabian Peninsula heavily relies on groundwater to meet the escalating demands of a growing population and expanding agricultural practices [5]. ...
This study addresses the imperative to comprehend gravity shifts resulting from groundwater storage (GWS) variations in the Arabian Peninsula. Despite the critical importance of water resource sustainability and its relationship with gravity, limited research emphasizes the need for expanded exploration. The investigation explores the impact of GWS extraction on the gravity field, utilizing Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) data in addition to validation using the WaterGAP Global Hydrology Model (WGHM). Spanning April 2002 to June 2023, this study predicts GWS trends over the next decade using the Seasonal Autoregressive Integrated Moving Average (SARIMA) model. The comprehensive time-series analysis reveals a significant GRACE-derived groundwater storage (GWS) trend of approximately −4.90 ± 0.32 mm/year during the study period. This trend has a notable impact on the gravity anomaly (GA) values, as observed through the decomposition analysis. The projected GWS indicates a depletion rate of 14.51 km³/year over the next decade. The correlation between GWS and GA is substantial at 0.80, while the GA and rainfall correlation is negligible due to low precipitation rates. Employing multiple linear regression explains 80.61% of the variance in gravity anomaly due to GWS, precipitation, and evapotranspiration. This study investigates climate change factors—precipitation, temperature, and evapotranspiration—providing a holistic understanding of the forces shaping GWS variations. Precipitation and evapotranspiration exhibit nearly equal values, limiting GWS replenishment opportunities. This research holds significance in studying extensive GWS withdrawal in the Arabian Peninsula, particularly concerning crust mass stability.
... In arid and semi-arid regions, numerical modeling of groundwater has become a relevant tool for proper groundwater management (Al-Salamah et al. 2011;Lachaal et al. 2012;Singh 2013;Garcia-Rodriguez et al. 2014;Yao et al. 2015;Bouaamlat et al. 2016); it is also an essential tool for estimating the impact of recharge and variation of groundwater for each period of the simulation (Chenini and Ben Mammou 2010;Tizro et al. 2011;Zume and Tarhule 2011;Tian et al. 2015). ...
The Ferkla Oasis is situated in the Rheris watershed in the southeast of Morocco, between the eastern Anti-Atlas in the south (Ougnat inlier) and the Central High Atlas in the north. This oasis is characterized by a semi-desert climate with strong continental influence, marked by low and irregular rainfall and high temperatures. This oasis has experienced several agricultural extensions outside the traditional oasis, resulting in overpressure on the groundwater as evidenced by the dramatic decline of its piezometric level, which has engendered an ecological and socio-economic crisis. In these critical conditions, a groundwater flow model was developed to evaluate the impact of climate change and anthropogenic activities on the hydrodynamic behavior of the aquifer. The results obtained confirmed that the region is increasingly threatened by groundwater resource scarcity. Indeed, simulations of the watershed in both a permanent and transient state were generated for the years 1993 through 2021. These simulations have shown a piezometric level decline, as well as a deficit in the water balance, as well as a deficit in the water balance. This situation is caused by climate effects, particularly frequent droughts, and the overexploitation of the groundwater resources, especially in the agricultural extension areas outside the traditional oasis. The study demonstrates that the oasis faces a serious crisis and may further deteriorate until it disappears within a few years. Therefore, integrated, collective, and participatory measures are recommended. The model provides important results that will aid in groundwater resource management in this region.
... This can be ascribed to the differences in geological structures and hydrometeorological conditions in these types of watersheds. Moreover, compared with humid areas, the frequent human exploitation for agricultural water utilization in arid areas makes the conversion of rivers and groundwater more complicated and challenging (Tian et al. 2015;Wang et al. 2018a). The results provided by the modes indicate that most of the groundwater contributions involved in the water circulation occur in shallow flow systems, and only a small proportion participates in deep flow systems. ...
River–groundwater interactions play a vital role in the hydrological cycle and have close hydraulic linkages, which domi-
nate the watershed macro-ecological processes in arid and semiarid areas. Based on the achievements of the team focusing
on interactions between rivers and groundwater over several years, as well as an assessment of the relevant literature, this
report summarizes six modes of river and groundwater interactions in the arid and semiarid areas of northwestern China.
The summary covers the dynamic processes of river–groundwater interactions controlled by geomorphic features and geo-
logical structures, including the recharge origin, flow path, flow velocity, water circulation amount, and discharge position
of the different modes. The ecological effects driven by river–groundwater interactions were analyzed from the basin-scale
perspective, as well as the human impacts of such interactions. The interaction between rivers and groundwater in the basin
manifests as the unity of the upstream, midstream, and downstream areas, which can be clearly divided into four belts,
namely, the mountainous belt, piedmont belt, channel belt, and plain belt. In addition, four belt regulation measures for the
utilization of water resources, with ecological protection as the goal, are proposed from a systemic viewpoint of watershed
water circulation. The results of this study could contribute to improved management plans for the joint development of
rivers and groundwater systems, and the related ecological environment, in arid regions to help cope with the increasing
pressures caused by water scarcity and intensive human activities.
... Recently, applications of GSFLOW and SWAT-MOD-FLOW, among MODFLOW-based coupled models, have been steadily increasing (Tian et al. 2015;Barthel and Banzhaf 2016;Moges et al. 2020b). Following the revision of the modeling framework by Bailey et al. (2016), the use of SWAT-MODFLOW for a range of environmental studies has spread widely. ...
River-aquifer interaction is a key component of the hydrological cycle that affects water resources and quality. Recently, the application of integrated models to assess interaction has been increasing. However, calibration and uncertainty analysis of coupled models has been a challenge, especially for large-scale applications. In this study, we used PESTPP-IES, an implementation of the Gauss-Levenberg–Marquardt iterative ensemble smoother, to calibrate and quantify the uncertainty of an integrated SWAT-MODFLOW model for watershed-scale river aquifer interaction assessment. SWAT-MODFLOW combines the Soil and Water Assessment Tool (SWAT), a widely used watershed model, with a three-dimensional groundwater flow model (MODFLOW). The calibration performance of the model was evaluated, and the uncertainty in the parameters and observed ensemble, including the uncertainty in forecasting groundwater levels, was assessed. The results showed that the technique could enhance the model performance and reduce uncertainty. However, the results also revealed some limitations and biases, such as overestimating the groundwater levels in most monitoring wells. These biases were attributed to the limited availability of groundwater level in the first year of the calibration and the uncertainty in groundwater flow model parameters. The river-aquifer interactions analysis shows that water exchange occurs in almost all cells along the river, with most of the high-elevation areas receiving groundwater and flatter regions discharging water to the aquifer. The study showed that PESTPP-IES is a robust technique for watershed-scale river-aquifer modeling that can ensure model calibration and parameter uncertainty analysis. The findings of this study can be used to improve water resources management in watersheds and help decision-makers in making informed decisions.
... When the continuous over-pumping of groundwater occurs, the recharge of groundwater cannot replenish the drawdown of the aquifers (Awaleh et al. 2017;de Vries and Simmers 2002;Mauser and Ludwig 2016). Not only the demand of groundwater is increasing, but rainfall and recharge to groundwater are also expected to decline in many semi-arid regions where irrigation mainly depends on groundwater (Tian et al. 2015). Groundwater is used as the water supply for various purposes in major Indonesian cities. ...
Lembang groundwater basin has an area of 209 km ² . Increased tourism activities in the Lembang Groundwater Basin require sufficient groundwater resources to support the sustainability of these tourism activities. The purpose of this study was to analyze the hydrostratigraphy of the groundwater recharge zone of the Lembang groundwater basin in the Cikole-Lembang. Electrical Resistivity Tomography (ERT) with dipole–dipole electrode array and seismic refraction was used to analyze the hydrostratigraphy. The results of ERT and seismic refraction inversion show that Tangkubanparahu Pyroclastic Fall 2 can be characterized as aquifers. This layer consists of low (123–292 $$\Omega $$ Ω m) and intermediate (293–700 $$\Omega $$ Ω m) resistivity value and also has low (300–1350 m/s) to medium (2700–1350 m/s) velocity. Tangkubanparahu lava (Tl) layer has a high resistivity value (701–3875 $$\Omega $$ Ω m) and high (1350–2999 m/s) velocity. The Tangkubanparahu Pyroclastic Fall 1 has a resistivity of 300–700 ohms. Tangkubanparahu (Tl) lava deposits can be characterized as fracture aquifer and impermeable layers in the Tangkubanparahu volcanic hydrogeological system depend on the historical structural geology event.
... The groundwater potential varies considerably both spatially and temporally, even within a single aquifer, leading to disparities in potential across different regions. This scarcity of groundwater has a multifarious impact on various aspects of agricultural and forest ecosystems, access to safe drinking water, public health, and ultimately, the livelihoods of the people (Cetin et al., 2023;Tian et al., 2015). The depletion of these precious resources in many regions across the world can be attributed to the overexploitation resulting from intensive agricultural practices and rapid developmental activities (Adiguzel et al., 2022;Döll et al., 2014;Tekin et al., 2022;Varol et al., 2022). ...
Groundwater is a vital natural resource that plays a critical role in sustaining agriculture, forest ecosystems, industry , and household uses. However, due to natural and anthropogenic factors, groundwater is facing alarming declines. Therefore, this study aimed to assess the potential groundwater zones (PGWZ) in the northeastern Ben-gal Basin of Bangladesh between 1990 and 2021 using satellite images, public and field data pertaining to ten environmental parameters. The study utilized analytical hierarchy process to identify PGWZ and evaluated the effectiveness of machine learning (ML) algorithms (K-nearest neighbors, support vector machine, XGBoost, decision tree, and random forest) for PGWZ classification. The findings indicated a decline in groundwater potential over the decades, which was categorized into five distinct zones based on the relative groundwater potential. The very high PGWZ decreased from 2.19% to 1.3%, and high PGWZ from 34.57% to 28.24%, while there was a sharp increase in the poor status of PGWZ (very low, low, and medium zones) over the same periods. The accuracy and kappa coefficients of the ground data validation for the estimated PGWZ map were 84.34% and 79.61%, respectively. According to accuracy, precision, recall, and f1-score, five ML models are reliable predictors of PGWZ. RF achieved the highest accuracy of 92.33%, while XGBoost achieved an accuracy of 90.31%. Both models demonstrated superior prediction performance for PGWZ based on the normalized leverage factor. The study attributes the alteration of groundwater potential to changes in land use and land covers, increased land surface temperatures, decreased rainfall, and changes in soil erosion in the study region over the three decades. The results of this study offer valuable insights for decision-makers to make informed decisions for the sustainable and responsible management of groundwater resources.
... Compared to the potential evapotranspiration, the reference crop evapotranspiration is clearer and more practical because its evaporation surface characteristics are explicitly qualified (Allen et al., 1998;Xiang et al., 2020). In recent years, an increasing number of scholars have used the reference crop evapotranspiration as the proxy for potential evapotranspiration (Joo et al., 2018;Tang & Tang, 2021;Tian et al., 2015). Moreover, many studies have shown that the reference crop evapotranspiration estimated by the FAO Penman-Monteith model agrees well with the apparent potential evapotranspiration measured by evaporation pans in wetted regions (M. ...
To better understand the changes in the atmospheric evaporative demand (AED) in the context of global warming, the anomaly contribution analysis is presented to estimate mid‐long term contributions of meteorological factors to the AED. The Pearson correlation coefficient (RP) between the total contribution (ψ) of meteorological factors and the relative variation (ϕ) of the AED, and the Sen's trend slope (βS) of (ϕ, ψ) scatters are used to evaluate the applicability of the method. The smaller the values of |1 − RP| and |1 − βS|, the more applicable the method is. To validate the method, the reference crop evapotranspiration is employed as a proxy for the AED. The multi‐year contribution analysis is used as a comparison approach, which can only investigate the dominant meteorological factors of the AED in long term. Moreover, the Huaihe River basin of China is taken as a case study. Results show that (a) the values of |1 − RP| and |1 − βS| in mid‐long term are less than 0.1 in most cases when applying the anomaly contribution analysis, and the mid‐long term contribution processes of meteorological factors to the AED are clearly demonstrated; and (b) the wind speed and sunshine hours are the two most dominant factors (the total absolute contribution exceeds 60%) in long term, but they are not always the dominant factors in mid‐long term (e.g., wind speed in summer, and sunshine hours in winter). Therefore, the anomaly contribution analysis is a reasonable and effective method, which can help to gain insights into the changes in the AED.
... The consumptive use is an indicator which shows the net amount of water being utilized by plant throughout its life span. The study of consumptive use and water available is also important to estimate the water requirement and accordingly plan and develop the water resources (Tian et al., 2015). Starr & Levison(2014)studied the consumptive use for different crops for Whiteman's creek watershed in Canada. ...
Water management is crucial in arid and semi-arid regions to maintain a sufficient and reliable water supply. The semi-arid Khatav taluka in Maharashtra, India, has an average annual rainfall of 554 mm. The various authors have used conjunctive usage of surface and groundwater for water resource management in such water-stressed areas. The purpose of this study is to correlate and estimate water yield and consumption in irrigation commands for the Khatav taluka. The SWAT (Soil and Water Assessment Tool) model was calibrated and validated using the SUFI-2 algorithm in the SWAT-CUP program to meet the desired aim. The SWAT model's actual evapotranspiration values were compared to those obtained using the modified penman method (MPM). The meteorological data from the IMD (India Meteorological Department) was utilized to process the SWAT model for the period (2000-2014). The results show that, average curve number for the research region is 86.81, and evapotranspiration was 461 mm. It was also discovered that the research area suffers from salinization since the rate of evaporation exceeds the rate of precipitation. This research aids in the identification of potential salinized areas as well as the forecasting and management of future water demand. Researchers and decision makers will be able to use the study's findings to manage and allocate water resources in a sustainable manner.
... In arid and semi-arid regions, numerical modeling of groundwater has become a relevant tool for proper groundwater management (Al-Salamah et al. 2011;Lachaal et al. 2012;Singh 2013;Garcia-Rodriguez et al. 2014;Yao et al. 2015;Bouaamlat et al. 2016); it is also an essential tool for estimating the impact of recharge and variation of groundwater for each period of the simulation (Chenini and Ben Mammou 2010;Tizro et al. 2011;Zume and Tarhule 2011;Tian et al. 2015). ...
The Ferkla Oasis is situated in the Rheris watershed in the southeast of Morocco, between the eastern Anti-Atlas in the south (Ougnat inlier) and the Central High Atlas in the north. This oasis is characterized by a semi-desert climate with strong continental influence, marked by low and irregular rainfall as well as high temperatures. This oasis has experienced several agricultural extensions outside the traditional oasis, resulting in overpressure on the groundwater as evidenced by the dramatic decline of its piezometric level, which has engendered an ecological and socio-economic crisis.
In these critical conditions, a groundwater flow model was developed to evaluate the impact of climate change and anthropogenic activities on the hydrodynamic behavior of the aquifer. The results obtained confirmed that the region is increasingly threatened by groundwater resource scarcity. Indeed, simulations of the watershed in both a permanent and transient state were generated for the years of 1993 through 2021. These simulations have shown a piezometric level decline, as well as a deficit in the water balance, as well as a deficit in the water balance. This situation is caused by climate effects, particularly frequent droughts, and the overexploitation of the groundwater resources, especially in the agricultural extension areas outside the traditional oasis.
The study demonstrates that the oasis faces a serious crisis and may further deteriorate until it disappears within a few years. Therefore, integrated, collective and participatory measures are recommended. The model provides important results that will aid in groundwater resource management in this region.
... The conjunctive use technique was used to dilute the polluted water and to have systematic irrigation planning in Tehran plain, Iran [9]. The stormwater management model (SWMM) and Groundwater and Surface water Flow Model (GSFLOW) were together used to improve water resource management in water scare regions [23]. The water shortage problem can be minimized with the help of conjunctive use of groundwater and surface water [22]. ...
... The consumptive use is an indicator which shows the net amount of water being utilized by plant throughout its life span. The study of consumptive use and water available is also important to estimate the water requirement and accordingly plan and develop the water resources (Tian et al., 2015). Starr & Levison(2014)studied the consumptive use for different crops for Whiteman's creek watershed in Canada. ...
Water management is crucial in arid and semi-arid regions to maintain a sufficient and reliable water supply. The semi-arid Khatav taluka in Maharashtra, India, has an average annual rainfall of 554 mm. The various authors have used conjunctive usage of surface and groundwater for water resource management in such water-stressed areas. The purpose of this study is to correlate and estimate water yield and consumption in irrigation commands for the Khatav taluka. The SWAT (Soil and Water Assessment Tool) model was calibrated and validated using the SUFI-2 algorithm in the SWAT-CUP program to meet the desired aim. The SWAT model's actual evapotranspiration values were compared to those obtained using the modified penman method (MPM). The meteorological data from the IMD (India Meteorological Department) was utilized to process the SWAT model for the period (2000-2014). The results show that, average curve number for the research region is 86.81, and evapotranspiration was 461 mm. It was also discovered that the research area suffers from salinization since the rate of evaporation exceeds the rate of precipitation. This research aids in the identification of potential salinized areas as well as the forecasting and management of future water demand. Researchers and decision makers will be able to use the study's findings to manage and allocate water resources in a sustainable manner.
... These modeling are based on the technique used such as linear/nonlinear programming, simulation and predictions, hierarchical optimization, and dynamic programming [23]. Conjunctive use modeling was carried out by [34] for arid and semi-arid regions in China. In this study, stormwater management model (SWMM) and groundwater and surface water flow model (GSFLOW) were coupled. ...
Optimization of conjunctive use of surface and groundwater has become a necessity aid in sustainable irrigation methods that supposed to opt in Khatav taluka of Maharashtra state, India. The study area falls under semi-arid condition and edged with water stressed which is having average annual rainfall of 560 mm. The main objective of this study was to formulate the model of conjunctive use of water and to restrict the water scarcity at the minimal extent along with maximum yields from agricultural practices. The set objectives were achieved by joint optimization techniques of LINGO and particle swarm optimization (PSO) where model has been run by using LINGO and validated by PSO. The conjunctive use of water was employed to overcome various constraints like volume of water, depth of groundwater, gross area of cultivation and total area under irrigation. The results of present study show its feasibility and the ease of applicability in such water sacred area, where conjunctive use of water in different seasons saves the surface water approximately up to 49% in the hot season, 27% in Kharif, and 32% in Rabi seasons. This study inferred that the cropping pattern has to be in ordered manner such that it can balance the available water resources. This can be done by lowering of crop productions other than sugarcane and onion by 12-15% which leads to increment of overall net returns approximately by 8% and more during above mentioned seasons.
... This creates a level of uncertainty within the model that cannot be accounted for without a detailed survey of well water extraction within the Six Nations reserve which is not within the scope of this study. Similar comments regarding incomplete pumping records have been made by Tian et al. (2015). ...
Introduction: This study explored streamflow dynamics of the McKenzie Creek watershed in Southern Ontario, Canada under a changing climate. The Creek is located in the southern portion of the Grand River watershed in the Great Lakes region and is an important water and ecosystem service provider for the Six Nations of the Grand River reserve, the largest (by population) Indigenous community in Canada and the fourth largest in North America.
Methods: The Coupled Groundwater and Surface-Water Flow Model (GSFLOW) was used to simulate streamflow from 1951 to 2020 using observed gridded meteorological data from Natural Resources Canada (NRCANmet) and in situ data from Environment and Climate Change Canada (ECCC). Downscaled data from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for two Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathways (RCP) climate warming scenarios, RCP 4.5 and RCP 8.5 were used to run GSFLOW for the historic (1951–2020) and projected (2021–2099) period.
Results: Results suggested that streamflow in the McKenzie Creek will be significantly impacted by climate change in winter months when streamflow is projected to increase due to higher temperatures causing early melting of snowpack and increasing winter precipitation. Consequently, spring streamflow is expected to decrease and little or no change in streamflow in the summer and autumn. These changes in streamflow dynamics may lead to more flooding incidents in the winter, while at the same time, the region may face reduced water availability or dry conditions in late spring and summer due to warm temperatures.
Discussion: This study provides important information about streamflow and hydrologic dynamics of this watershed that will help managers and planners to better manage water resources and be prepared to deal with climate change and its impacts on water availability and security not only for the Six Nations area but also for Southern Ontario which houses one-third of Canada’s population.
... The role of groundwater as a buffer to environmental changes has, thus, been widely acknowledged and investigated [9,10]. Surface water and groundwater bodies comprise integral parts of the hydrologic cycle, with a strong influence on their water budgets [11,12]. This indicates that a more realistic evaluation of climate change impacts on surface water resources should consider the changes in groundwater bodies, and vice versa. ...
We investigated the potential impact of observation error on the calibration performance of an integrated watershed model. A three-dimensional integrated model was constructed using HydroGeoSphere and applied to the Sabgyo watershed in South Korea to assess the groundwater–surface water interaction process. During the model calibration, three different weighting schemes that consider observation error variances were applied to the parameter estimation tool (PEST). The applied weighting schemes were compared with the results from stochastic models, in which observation errors from surface discharges were considered a random variable. Based on the calibrated model, the interactions between groundwater and surface water were predicted under different climate change scenarios (RCP). Comparisons of calibration performance between the different models showed that the observation-error-based weighting schemes contributed to an improvement in the model parameterization. Analysis of the exchange flux between groundwater and surface water highlighted the significance of groundwater in delaying the hydrological response of integrated water systems. Predictions based on different RCP scenarios suggested the increasing role of groundwater in watershed dynamics. We concluded that the comparison of different weighting schemes for the determination of error covariance could contribute to an improved characterization of watershed processes and reduce the model uncertainty arising from observation errors.
... Additionally, it is noteworthy that the water cycle is closed in the inland rivers, which makes the Heihe River Basin an ideal study area to explore regional hydrological processes [36]. Previous studies have mainly focused on how to regulate and optimize water resources and management [37][38][39][40]. Investigations on groundwater-surface water interactions and corresponding hydrological responses during the process of overland flow generation are still in progress in the Heihe River Basin. ...
Groundwater-surface water interactions play a crucial role in hydrologic cycles, especially in arid and semi-arid basins. There is a growing interest in developing integrated hydrologic models to describe groundwater-surface water interactions and the associated processes. In this study, an integrated process-based hydrologic model, ParFlow, was tested and utilized to quantify the hydrologic responses, such as changes in surface runoff and surface/subsurface storage. We progressively conducted a complexity-increasing series of benchmarking cases to assess the performance of ParFlow in simulating overland flow and integrated groundwater-surface water exchange. Meanwhile, the overall performance and the computational efficiency were quantitatively assessed using modified Taylor diagrams. Based on the benchmarking cases, two case studies in the Heihe River Basin were performed for further validation and to diagnose the hydrologic responses under disturbance, named the Bajajihu (BJH) and Dayekou (DYK) cases, respectively. Both cases were 2D transects configured with in-situ measurements in the mid- and downstream of the Heihe River Basin. In the BJH case, simulated soil moisture by ParFlow was shown to be comparable with in-situ observations in general, with Pearson’s correlation coefficient (R) > 0.93 and root mean square difference (RMSD) < 0.007. In the DYK case, seven scenarios driven by remote sensing and reanalysis data were utilized to study hydrological responses influenced by natural physical processes (i.e., precipitation) and groundwater exploitations (i.e., pumping) that are critical to surface and subsurface storage. Results show that subsurface storage is sensitive to groundwater exploitation before an obvious stationary point. Moreover, a correlation analysis was additionally provided demonstrating the impacts of different factors on subsurface storage timeseries. It was found that pumping influences subsurface storage remarkably, especially under short-term but large-volume pumping rates. The study is expected to provide a powerful tool and insightful guidance in understanding hydrological processes’ effects in arid and semi-arid basins.
... To address these concerns and their effects on deltas, understanding the complex interaction of groundwater (GW) and surface water (SW) and the way they are affected by groundwater over-abstractions and agricultural activities (including canalization for irrigation) is crucial (Tian et al., 2015). For better management, quantifying and modeling the cause and effect of the various components, coupled with the uncertainty and human responses, requires attention and further research (Li et al., 2017). ...
Many of the world's deltas are highly productive areas for agriculture as well as important places of socioeconomic development but are currently under stress. This study assesses the impacts of stresses on groundwater pumping, changing cropping patterns, and saltwater intrusion on groundwater resources in the Cauvery Delta in Tamil Nadu, India. A transient groundwater flow model of the delta was constructed for this assessment. The historical changes in groundwater resources in response to decreasing irrigation canal flows and increasing groundwater abstractions were assessed for the past 30 years. Furthermore, the model was used to formulate and analyze future sustainable groundwater development scenarios. Farmers' narratives about a drying delta, as they experience water scarcity and quality issues most closely, were ascertained in the research. Farmers have abandoned many shallow wells in their fields. The model simulation shows groundwater levels are decreasing and aquifer storage depleting. Furthermore, salinization has increased, with continuous declining groundwater levels in the deep aquifer from 1990 to 2019. A more robust hydro-chemical assessment and further modeling of seawater intrusion are needed to better assess the sources and distribution of groundwater salinity. The pathway for future sustainability requires enhancing groundwater recharge in the shallow aquifer and controlling groundwater abstraction in the deep aquifers.
... -Understanding the mechanism of groundwater and surface water interactions (Fleckenstein et al. 2010;Dawoud and Ismail 2013;El-Rawy et al. 2016, 2021a, 2021b. Tian et al. (2015) coupled groundwater and surface water flow model (GSFLOW) with storm water management model to study the groundwater system along with the hydrologic cycle in the Zhangye Basin, northwest China. Polomčić and Bajić (2015) used the groundwater modeling to decide the best scenario of the dewatering process in the Buvač open cast mine, Bosnia and Herzegovina. ...
Groundwater plays an essential role in the overall management of water resources. The demand for groundwater for municipal, agricultural, and industrial use has been grown steadily during the past decades. Groundwater modeling can be used to evaluate the quantity and quality of groundwater in aquifer-aquitard systems, also in relation to environment and climate change. Modeling allows for the construction of scenarios based on different groundwater abstraction rates, changes in human activities, and varying environmental conditions. Models can be based on simple analytical methods and comprehensive finite difference or finite element methods, dependent on the model’s purpose and the available data. Conceptualization and data collection strongly influences the choice of the numerical model. In the past finite difference and finite element methods were considered as completely different, but more recent developments closed the gap between these two methods. Generally, the time-independent data like spatially distributed hydraulic conductivities, etc. are not available at the start of the modeling. These parameters have to be determined from a time series of both measured and calculated quantities, for instance hydraulic heads, This process is generally called model calibration, or parameter estimation. Groundwater modeling is intending to represents reality in a simplified form, without making too simple assumptions for the purpose of the modeling study; for instance scenarios to investigate the response of an aquifer-aquitard system for a number of hypothetical phenomena like, for instance flash rains or excessive droughts. Several numerical groundwater flow models have been developed for different parts of the Nile Valley aquifer to assess the interaction between the surface water and the aquifer, to apply various management recharge and discharge scenarios. All studies have shown that groundwater modeling can be used successfully to help understand the Nile Valley aquifer's behavior.
... However, this food supply is threatened by the continuous reduction in the availability of water for agricultural use due to global warming and the competition with other sectors, such as manufacturing water use, public water supply or energy production (Flörke et al., 2018;Ringler et al., 2013;Rosegrant and Ringler, 2000). Besides, in semiarid regions, these water limitations can be especially important, even more in a climate change context (Elliott et al., 2014;Tian et al., 2015). For example, in important agricultural areas, such as Castilla-La Mancha (CLM) in Spain, reductions of irrigation water extraction are already a fact (Martínez-Romero et al., 2021). ...
Agriculture must improve the productivity of irrigation water due to several factors, such as global warming, the increasing water demand of other sectors or the protection of the environment. The “optimized regulated deficit irrigation for limited volumes of water” (ORDIL) methodology may contribute to reach this objective by optimizing the allocation of irrigation water during the growing cycle, when the available volume is lower than the crop irrigation requirements. ORDIL was applied to a barley crop in a 3-year (2015–2017) field test under the semiarid conditions of Albacete (Spain). The main aim was to assess the influence of ORDIL on the physiological response of barley. The specific objectives were: 1) Identify if stomatal conductance (gs), net assimilation rate (An), intrinsic water use efficiency (WUEi) and total dry matter (TDM) evolution can be used as early and sensitive indicators of barley water status and crop performance; 2) Provide a mechanistic basis to understand barley physiological response to deficit irrigation at the most sensitive stages and; 3) Evaluate barley physiological response to ORDIL and its relation with yield. Thus, five irrigation treatments were performed. One without deficit (ND), and four with limited volumes of irrigation water (100%, 90%, 80% and 70% of typical irrigation needs). According to the results, gs was a reliable variable to detect early water deficit in barley. Besides, critical thresholds for this variable were found to optimize irrigation and to avoid chronic physiological damages affecting the most sensitive and yield-related stages. In summary, the physiological approach applied in this study validates ORDIL methodology being useful for future irrigation scheduling and distribution improvements.
... Impacts of groundwater withdrawal on stream aquifer interaction are reduction in aquifer discharge and increase in river leakage, so the river changes its behavior from gaining to losing. The model used to simulate the impact of well pumping on stream aquifer interaction are (Chen and Yin, 2001;Chen and Shu, 2002;Zume and Tarhule, 2008;Tian et al. 2015;Lee et al. 2017;Stefania et al. 2018). ...
The river aquifer interaction model was developed for the waterlogged-alluvial aquifer to address the issues of the lower river leakage and higher aquifer discharge in the waterlogged groundwater system. The developed model was simulated and calibrated for the 15 years simulation period (2006–2020). From the model study, it is observed that river aquifer interaction changes seasonally, river leakages to the aquifer in the monsoon period and aquifer discharges to the river in the rest period. From the analysis, it is visualized that the monthly variation in river aquifer interaction majorly depends on the river stage. From the analysis, it also concluded that the value of river leakage is low as compared to aquifer discharge caused due to aquifer waterlogging. The model was further applied to reduce the waterlogged area to a certain degree by introducing sustainable groundwater irrigation from the waterlogged aquifer during the dry/Rabi season. Thus, the fraction of uncultivated land near the river flood plain converted as agricultural land. Sustainability is achieved by considering the three scenarios to unaltering the river aquifer interaction seasonally. The three scenarios are introducing groundwater irrigation to convert (i) 25%, (ii) 50% and (iii) 75% of the uncultivated land to agricultural land. It is revealed from the study that the sustainable proposed scenario is where the agricultural land equals to 75% of uncultivated land. The proposed methodology has been illustrated in the alluvial flood plain of the Barak river in Cachar, Assam, India.
... Owing to a rapid increase in the growth of computing and the wide availability of computers and modeling software from the early 2000s, many physically based, fully integrated SW-GW models have been developed for water resource research and management [16,20]. The integrated models provide both detailed spatial and temporal descriptions of the basin-scale hydrologic cycle and can simulate a variety of state and flux variables and have been applied in various hydrology studies in different parts of the world [1,20,[23][24][25][26][27][28][29][30]. Therefore, a variety of coupled SW and GW models have evolved over the years, such as GSFLOW [19], MIKE-SHE [23], and several SW models integrated into MODFLOW, such as MODBRANCH [28], SWATMOD [29], MODHMS [30], VIC-MOD-FLOW [16], and TOPMODEL-MODFLOW [31]. ...
This study attempts to integrate a Surface Water (SW) model Soil and Water Assessment Tool (SWAT) with an existing steady-state, single layer, unconfined heterogeneous aquifer Analytic Element Method (AEM) based Ground Water (GW) model, named Bluebird AEM engine, for a comprehensive assessment of SW and GW resources and its management. The main reason for integrating SWAT with the GW model is that the SWAT model does not simulate the distribution and dynamics of GW levels and recharge rates. To overcome this issue, often the SWAT model is coupled with the numerical GW model (either using MODFLOW or FEFLOW), wherein the spatial and temporal patterns of the interactions are better captured and assessed. However, the major drawback in integrating the two models (SWAT with-MODFLOW/FEM) is its conversion from Hydrological Response Unit's (HRU)/sub-basins to grid/elements. To couple them, a spatial translation system is necessary to move the inputs and outputs back and forth between the two models due to the difference in discretization. Hence, for effective coupling of SW and GW models, it may be desirable to have both models with a similar spatial discretization and reduce the need for rigorous numerical techniques for solving the PDEs. The objective of this paper is to test the proof of concept of integrating a distributed hydrologic model with an AEM model at the same spatial units, primarily focused on surface water and groundwater interaction with a shallow unconfined aquifer. Analytic Element Method (AEM) based GW models seem to be ideal for coupling with SWAT due to their innate character to consider the HRU, sub-basin, River, and lake boundaries as individual analytic elements directly without the need for any further discretization or modeling units. This study explores the spatio-temporal patterns of groundwater (GW) discharge rates to a river system in a moist-sub humid region with SWAT-AEM applied to the San Jacinto River basin (SJRB) in Texas. The SW-GW interactions are explored throughout the watershed from 2000-2017 using the integrated SWAT-AEM model, which is tested against stream flow and GW levels. The integrated SWAT-AEM model results show good improvement in predicting the stream flow (R 2 = 0.65-0.80) and GW levels as compared to the standalone SWAT model. Further, the integrated model predicted the low flows better compared to the standalone SWAT model, thus accounting for the SW-GW interactions. Almost 80% of the stream network experiences an increase in groundwater discharge rate between 2000 and 2017 with an annual average GW discharge rate of 1853 Mm 3 /year. The result from the study seems promising for potential applications of SWAT-AEM coupling in regions with considerable SW-GW interactions. Citation: Sangeetha,K.; Narasimhan, B.; Srinivasan,R. A Coupled SWAT-AEM Modelling Framework for a Comprehensive Hydrologic Assessment. Water 2022, 14, 2753. https://
... Generally, most studies attempt to infer hydrological exchanges through multi-method approaches; however, the appropriateness of each method is strongly dependent on specific hydrogeological settings and a range of spatio-temporal conditions (Khan & Khan, 2019;Levy & Xu, 2012;Sophocleous, 2002). Common approaches include a combination of modelling (Ellis et al., 2007;Tanner & Hughes, 2015;Tian et al., 2015), seepage meters and mini-piezometers (Baxter et al., 2003;Brodie et al., 2009;Oxtobee & Novakowski, 2002), hydrograph separation (Killian et al., 2019;Madlala et al., 2019), and time-series temperature measurements (Conant, 2004;Schmidt et al., 2007), amongst others (Coluccio & Morgan, 2019;Kalbus et al., 2006;Toran, 2019). For these studies, the use of environmental tracers, consisting of naturally occurring or man-made compounds, i.e., isotopes, dissolved ions, and in situ physical properties of water describe water quality variations serve as effective indicators of mixing dynamics between water resources (Elliot, 2014;Winter et al., 1998). ...
The growing importance of groundwater as a freshwater supply in semi-arid areas such as the Vredefort Dome World Heritage Site (VDWHS) demands the judicious management and development of this vital resource. The increased demand for groundwater due to the contamination of surface water, coupled with the lack of information on hydrological interaction and associated water quality implications, present difficulties in establishing management strategies. An integrated study based on hydrochemistry and multivariate statistical techniques supplemented by environmental isotopes delineated discrete areas of surface water and groundwater interaction in a fractured-rock terrain. Surface water loss was observed in sections that exhibited declining groundwater levels, whereas limited baseflow was restricted to zones with stable groundwater levels. The multivariate statistical analysis revealed the combined effect of natural hydrochemical processes and anthropogenic sources as controlling factors of water composition, and highlighted zones of aquifer-river water mixing, where certain areas were found to be additionally polluted by human-derived contaminants. The stable isotope (¹⁸O and ²H) ratios confirm mixing between depleted groundwater and enriched river water, producing a composition that reflected an integration of the isotopic variations. The continuous wastewater discharge into the Vaal River combined with the increased groundwater exploitation may be prompting induced recharge conditions. The results suggest compartmentalization of the groundwater systems, where certain areas within 1 km of the channel were not influenced by river-induced contamination. This indicates that hydrological connectivity is governed by site-specific hydraulic properties. This study shows the usefulness of a multi-method approach by combining environmental isotopes, hydrochemistry, and multivariate statistics to characterize hydrological linkage in semi-arid regions.
... These problems include excessive shallow groundwater withdrawal for agricultural and domestic uses in arid and semi-arid environments. [23][24][25] Shallow groundwater is the principal industrial, agricultural and domestic water supply. [26][27][28] In some remote communities, shallow groundwater is the principal source of community water supply during the dry season. ...
This study assessed shallow groundwater in rural Kebbi State using Pearson’s Correlation
(r), Factor Analysis (FA), and Hierarchical Cluster Analysis (HCA). One hundred (100)
shallow groundwater samples were drawn randomly from hand-dug shallow wells in 10
Local Government Areas (LGAs). Physical parameters (pH, temperature, TDS, EC, salinity)
were analysed in situ using hand-held metres. Separate water samples were taken to analyse
ions (Fe, Zn, K, Mg, Mg, HCO3
, Ca). Results revealed that shallow groundwater is lightly
acidic, except in Zuru and Fakai LGAs, where an alkaline condition occurred. Correlation
analysis revealed that the dissolved solids in shallow aquifers result from natural geological
and anthropogenic influences. However, FA had shown that most of the variability in
shallow groundwater is influenced by natural geological factors with little evidence from
anthropogenic inputs. The HCA categorised shallow groundwater into three groups: those
shallow wells having higher concentrations of Zn and Cl with more elevated salinity and
temperature; those shallow wells having very low salinity in central Kebbi State, and those
shallow aquifers having alkaline waters. Except for higher Fe and Zn concentrations, the
shallow aquifers contained water of excellent quality for drinking. Correlation analysis, FA,
and HCA present simple statistical tools for assessing the hydrochemistry of groundwater.
... The magnitudes of DMETREF-ETo sa and PET (Figs. 11 and 12) are different in the dry and wet seasons. This is in contrast with Tian et al. (2015) and Joo et al. (2018) studies that suggested FAO-ETo as a reliable method to estimate PET for integrated hydrological modelling in arid and semi-arid areas. The FAO-ETo addresses just one specific land cover type of hypothetical grass at specific climate and well-watered conditions, which for example in dry season reveals overestimation of a grass ETo but underestimation of an evergreen forest ETo. ...
Study region
Zamra catchment, Upper Tekeze Basin, Northern Ethiopia.
Study focus
Direct field estimates of potential evapotranspiration (PET) remain a challenge, because they are expensive and have limited spatial representativeness. An alternative is to derive PET by remote sensing as a product of reference evapotranspiration (ETo) and land use-land cover (LULC) factor (Kc). The aims of this study were to: i) validate satellite-derived Daily Reference Evapotranspiration (DMETREF-ETos); ii) correct the advection-bias of DMETREF-ETos as compared to in-situ FAO Penman-Monteith ETo (FAO-ETog); and iii) convert the bias-corrected DMETREF-ETos into PET. Four ATMOS 41 weather stations were installed and 1-year daily data was used to validate the DMETREF-ETos. The wet season actual evapotranspiration from FAO Water Productivity Open-access portal (WaPOR) was used to validate PET.
New hydrological insights for the region
Evaluation of DMETREF-ETos showed large underestimation biases when compared to FAO-ETog derived from in-situ weather stations, particularly in warm conditions, due to unaccounted advection-bias. The bias correction was performed as a function of near-surface air temperature obtained from ERA5-Land, merged with in-situ air temperature; the results showed substantial improvement of ETo. Finally, the daily PET was estimated by multiplying the corrected DMETREF-ETos by a spatio-temporally variable Kc, defined as linearly dependent on the NDVI obtained from Sentinel 2. This study emphasized substantial difference between ETo and PET, implying that the ETo cannot substitute PET, which in many hydrological studies is still a common practice.
... The majority of the previous studies about spatial-temporal variations of groundwater-surface water interactions have primarily focused on aquifer-river water interactions (Dibaj et al., 2021;Guevara-Ochoa et al., 2020a;Jafari et al., 2021b;Kurylyk et al., 2014;Saha et al., 2017;Schilling et al., 2021;Scibek et al., 2007;Sterte et al., 2018;Tian et al., 2015;Yang et al., 2017) and aquifer-lake water interactions (Elsawwaf et al., 2014;Kim et al., 2020;Smerdon et al., 2007;Vaheddoost and Aksoy, 2018;Xu et al., 2021;Yihdego et al., 2016). However, for watershed-scale areas possessing both regional-scale floodplain lake and complex river system, previous studies about groundwater-surface water interaction are less and generally take the water interchanges of groundwater with lake and river as a whole, without considering the difference of the temporal variation pattern of the groundwater-lake water interchange and that of the groundwater-river water interchange, and without considering the allocation pattern of groundwater discharges into rivers and lakes (Ala-aho et al., 2013;Li et al., 2019;Nixdorf, 2019;Yang et al., 2020;Yang et al., 2021;Yang et al., 2019). ...
For areas possessing both regional-scale floodplain lakes and complex river system, the allocation pattern of water interchange between the groundwater and the lakes and rivers, as well as its temporal variations under year-scale climate changes, are important issues in regard to water resources and ecology environment but are rarely revealed. This study presented a numerical groundwater modeling of the Poyang Lake area to reveal the difference of the temporal variation patterns of the groundwater-lake water interchange and that of the groundwater-river water interchange, and to assess the potential effects of year-scale climate on the temporal-spatial variability of water interchange and on the allocation pattern of the net groundwater discharges into rivers and lake. It is found that the monthly groundwater discharge into surface water exhibits significant temporal variability, which reveals an inverse correlation between monthly groundwater discharge and lake water levels and precipitation amounts. Rainy months can lead to groundwater recharge from the Poyang Lake. Our simulated results reveal that, in the dry year of 2018, the variable monthly groundwater discharge into Poyang Lake and the monthly groundwater recharge from Poyang Lake were 0.97–9.67 × 10⁸ m³/month and 0.07–2.54 × 10⁸ m³/month, respectively. Additionally, the annual water interchange amount between groundwater and the Poyang Lake was 9.44 × 10⁸ m³/year, and the annual net groundwater discharge into Poyang Lake was 6.76 × 10⁸ m³/year. However, the hydraulic interaction between groundwater and the five rivers only features groundwater discharge into rivers with variable monthly groundwater discharge into the five rivers of 0.20–0.72 × 10⁸ m³/month and an annual total groundwater discharge amount of 5.32 × 10⁸ m³/year in 2018. Additionally, our water interchange results of the rainy year of 2010 indicate that the annual water interchange amount between groundwater and the Poyang Lake was 22.74×10⁸ m³/year, the annual net groundwater discharge into the Poyang Lake was 1.26×10⁸ m³/year, and the annual groundwater discharge into the five rivers was 8.10 × 10⁸ m³/year. These comparisons between the results of the rainy year of 2010 and dry year of 2018 can reveal the effects of the year-scale climate on water exchange between groundwater and surface water and imply that a rainy year can increase the total water interchange amount but decrease the total net groundwater discharge into surface water and that groundwater is more likely to discharge into rivers during a rainy year. Furthermore, it is found that a rainy year can significantly alter the spatial distribution of the water interchange between groundwater and lake water and that the backward particle tracking simulation could be helpful in regard to identifying the spatial distribution of water exchange between groundwater and regional-scale lake. These findings can contribute to a deeper understanding of climate effects on the spatial-temporal variability of water interchange between groundwater and surface water in regional floodplain lake areas and provide supportive information for the evaluation of local water resources and the estimation of pollutant transportation.
... Stockholm Environmental Institute introduced this software in 1998 for the first time. WEAP can simulate water demand and supply, runoff, evapotranspiration, infiltration, irrigation demand, ecosystem services, water storage in groundwater and surface water, and operation rule for reservoirs (Tian et al. 2015;Kaddoura and el Khatib 2017). WEAP is an object-oriented model which is used in agricultural and rural systems in a basin or multireservoir systems (Ashrafi and Mahmoudi 2019). ...
The primary impediment to adopting the Water, Energy, and Food (WEF) Nexus is a lack of a comprehensive and user-friendly simulation model. According to our search on Google Scholar and the Scopus databank, WEF Nexus studies can be divided into three broad categories: (1) studies about the nexus concept, (2) studies related to nexus modeling and software development, and (3) case studies. Given that the present study’s objective is to review various solutions for WEF Nexus modeling and also to prepare a checklist of available models to find a better model for nexus simulation, we excluded papers and studies which were related to the nexus concept. After that, we split up other papers that talked about nexus and software development into (1) integrated and (2) compiled approaches. Then, it was attempted to identify the shortcomings in each approach. It was shown that the existing integrated WEF Nexus models (such as MUSIASEM, NexSym, CLEW, and ANEMI) had some significant drawbacks compared to compiled alternatives. Several of the major shortcomings of existing integrated models include the following: (1) They did not cover all spatial scales; (2) they included only a limited number of interactions across WEF subsystems; and (3) some of these models were unavailable. Therefore, as a general result of the current study, it was shown that compiled approach is generally preferable compared to available integrated models. In this regard, we tried to find the best water simulation models to implement in the nexus concept. We searched for papers about water simulation models and defined water subsystem requirements in the nexus concept. So, we evaluated each water simulation model based on its ability to cover water subsystem requirements. This work illustrates the capability of a suitable water simulation model to be utilized in the nexus concept and provides a holistic checklist to choose the preferred water simulation model based on the needs of each issue.
Groundwater–surface water interaction is greatly affected by surface topography and agricultural activities in managed agricultural regions. Such an interaction increases the complexity of hierarchical groundwater flow systems. However, the combined effects of microtopography and agricultural activities on groundwater flow patterns remain unclear. In this study, an integrated groundwater–surface water model was used to quantify the impact of microtopographic variations on groundwater flow patterns in an agricultural region in northwest China. Numerical experiments were conducted under different scenarios representing various degrees of microtopography. The results indicated that microtopography plays a pivotal role in the transfer of signals from spatiotemporally varying surface processes to the groundwater flow. Without consideration of the microtopography, the stationary fractional Gaussian noise–type infiltration processes in the vadose zone–saturated zone interface may be incorrectly simulated as non-stationary fractional Brownian motion. Furthermore, fractal analysis reveals that the scaling exponents of the pressure head are highly sensitive within the vadose zone and local flow subsystems. Microtopography plays an important role in shaping the groundwater response time (GRT) pattern, which results in a smaller average GRT but a larger core range. Contrarily, neglecting microtopography may lead to overestimation of the water table ratio (WTR), resulting in erroneous identification of groundwater patterns as topography-controlled types. This study highlights the importance of microtopography in the formation and evolution of nested groundwater flow systems and provides guidance for groundwater–surface water interaction simulations in managed regions.
Accurate estimation of seepage losses in large-scale canal systems and identification of their impact factors are important for improving water conveyance efficiency in agricultural districts. However, seepage losses can vary widely across different regions and periods, making it difficult to obtain a complete understanding of the variation process based solely on local scale studies. In addition, although there are currently some complex numerical models available for large-canal systems in agricultural districts, they are rarely used in practice due to their complexity. This study evaluated the regional-scale spatio-temporal seepage processes of the Zaohuo canal, a 55 km's sub-main earthen canal located in the Hetao Irrigation District, China, under current and future water-saving conditions using MODFLOW-SWR. In addition, a pre-processing tool was developed to process spatial geographic data and spatial topology between different canals. Furthermore, the sensitivity of different influencing factors, such as the permeability of canal bed sediments, surface and groundwater level, and local lining, was also investigated. The optimal relationship between lining areas when partial lining is used and seepage losses was also investigated. The calculated water conveyance efficiency coefficient is 0.7871, which fits well with the reported results and proves the reliability of the simulation. In addition, it was found that seepage losses are most sensitive to the surface water level of the canal, followed by the permeability of canal bed sediments and then the groundwater level. Moreover, new hybrid lining can reduce the seepage losses by about 92.02%, but ongoing maintenance is vital. When lining the key portion of the canal, the seepage losses will be significantly reduced with the increase of lining area. The seepage losses reduction factor increases by 5.8% for every 1 × 10 5 m 2 increase in lining area when the lining area is below 1 × 10 6 m 2 , while the effect is not significant when that limitation is exceeded. This study can support decision-making for water-saving projects in large water conveyance canals in regional-scale agriculture districts.
Water resource evaluation, management, and conservation at the local, national, and international levels depend on an accurate understanding of the hydrological processes. In data-poor environments and topographically complicated areas like the Ghba subbasin in the headwaters of the Nile River, the function of hydrological models is crucial. The primary goal of this study is to use the WEAP model to simulate the hydrology of the Ghba basin. This is because recent hydrological behaviour has changed significantly and resulted in a serious water deficit. The minimal satisfactory performance limit for the monthly stream flow variable was strongly attained by the multi-variable calibration scenario (R 2 = 0.82, NSE = 0.82, IA= 0.80 RSR = 0.87 and PBIAS = 9 % for calibration scenario; and R 2 = 0.78, NSE = 0.81, IA= 0.70 RSR = 0.80 and PBIAS = 11.5 % for validation scenario). Evapotranspiration makes up 63.4% of the water balance, according to the model simulation, while surface runoff, interflow, baseflow and groundwater recharge accounting for 11.1 %, 11.8%, 5.4% and 8.3 %, respectively. The simulated average annual streamflow at the subbasin outlet is 16.33 m 3 /s. The simulated monthly minimum flow occurs in January with an average flow of 1.78 m 3 /s and a coefficient of dispersion of 0.45. Maximum flows occur in July and August, with an average flow of 53.57 m 3 /s and a coefficient of dispersion of 0.19. The main rainy season was shown to have a larger spatial distribution of simulated runoff, and the average annual recharge value is 53.5 mm. The study's conclusions indicated that both surface water harvesting and groundwater extraction might be used for reliable water distribution to the subbasin's continuously increasing sectoral water demand.
River-aquifer interaction is a key component of the hydrological cycle that affects water resources and quality. Recently, the application of integrated models to assess the interaction has been increasing. However, calibration and uncertainty analysis of coupled models has been a challenge, especially for large-scale applications. In this study, we used PESTPP-IES, an implementation of the Gauss-Levenberg-Marquardt iterative ensemble smoother, to calibrate and quantify the uncertainty of an integrated SWAT-MODFLOW model for watershed-scale river aquifer interaction assessment. SWAT-MODFLOW combines the Soil and Water Assessment Tool (SWAT), a widely used watershed model, with a three-dimensional groundwater flow model (MODFLOW). The calibration performance of the model was evaluated, and the uncertainty in the parameters and observed ensemble, including the uncertainty in forecasting groundwater levels, was assessed. The results showed that the technique could enhance the model performance and reduce uncertainty. However, the results also revealed some limitations and biases, such as overestimating the groundwater levels in most monitoring wells. These biases were attributed to the limited availability of groundwater level in the first year of the calibration and the uncertainty in groundwater flow model parameters. The river-aquifer interactions analysis shows that water exchange occurs in almost all cells along the river, with most of the high-elevation areas receiving groundwater and flatter regions discharging water to the aquifer. The study showed that PESTPP-IES is a robust technique for watershed-scale river-aquifer modeling that can ensure model calibration and parameter uncertainty analysis. The findings of this study can be used to improve water resources management in watersheds and help decision-makers in making informed decisions.
The estimations and projections for the global population show that the population is rising dramatically. Because of this, meeting the demands for infrastructure, food, and domestic and industrial water for such a large population is a critical issue for many nations. In addition, the quality and quantity of the water resources are declining as a result of overuse, climate change, and population growth. These alarming situations require an intermediate intervention to conserve and optimize the water uses. The conjunctive use of surface water and groundwater is an old but less emphasized technique practiced in many countries to fulfill human needs partially. Conjunctive use of water has the advantages such as the utilization of poor/ saline water, maintaining the groundwater levels, reduction in waterlogging and secondary soil salination, reliable water availability, and increase in crop production. In line with these advantages, this study reviews the literature regarding the conjunctive use of surface and groundwater for sustainable development of irrigated agriculture. The global scenario of water resources and how the conjunctive water use aids sustainable development is first reported. Climate change, groundwater quality and conjunctive use for various basins are discussed in detail. The capabilities of various simulation-optimization models to plan water resources efficiently are presented with case studies. Reported studies indicate that by practicing the conjunctive use not only water resources are conserved but the issues like secondary soil salination and waterlogging are alleviated. The research gaps and conclusions are provided based on the literature review that may be useful for policymakers and researchers for future research and to plan the water resources sustainably.
Groundwater exploitations in semi‐arid regions result in significant declines of groundwater levels and streamflow and even trigger seasonal streamflow drying up, which may bring adverse impacts on riparian ecosystems. It is critical to explore future streamflow changes caused by variable climate scenarios and groundwater exploitation intensities; however, a comprehensive assessment of the streamflow drying up frequency remains lacking. Furthermore, the thresholds of controlling factors beyond which streamflow drying up occurs have rarely been explored. Here we develop an integrated surface water‐groundwater model for the Taoer River Basin (TRB), a typical semi‐arid watershed in northeast China. We apply the model to multiple future scenarios to reveal the frequency of potential streamflow drying up and explore the thresholds of controlling factors of streamflow drying up based on a decision tree method. We find that the groundwater level in the lower region of the TRB (LTRB) is hard to recover to the riverbed elevation and the streamflow drying up frequency is still high unless the groundwater exploitation is reduced by 50%. However, this leads to a competition between the ecological and economic objectives. Our results also show that the streamflow drying up frequency in the LTRB is very sensitive to the upstream water inflow that can be regulated through the reservoir operation or inter‐basin water diversion, indicating the importance of a basin scale strategic management. The findings of this paper can help policy makers sustainably exploit water resources in semi‐arid regions.
Study region
The Aswan region is a vast plateau in the South of Egypt located 150 m above mean sea level (AMSL). Within this region, the tourist city of Aswan is Egypt’s southernmost city, located on the east bank of the Nile River.
Study focus
The occurrence of flash floods can severely impact low-lying and densely populated areas. Therefore, highly vulnerable areas require effective mitigation measures to guarantee public safety and preserve archeological sites of great importance. This study investigates the interaction between the soil, surface water, and groundwater in the Aswan region of Egypt. Based on the rainfall analysis and the watershed hydrology, six different scenarios were run using the MODFLOW and Watershed Modeling System (WMS) software, which simulated rainfall recurrence intervals of 2, 5, 10, 25, 50 and 100 years.
New hydrological insights for the region
The model's results indicated that an increase in the recurrence interval produced a rise in the groundwater level (GWL) up to 8.82 m (AMSL). Therefore, constructing three dams was proposed as a solution at the three basins of Al- Haytah, Al-Kimab, and Umm-Buwayrat. The proposed solution allows the storage of large volumes of water upstream. It mitigates GWL's rise within and near Aswan City. The presented study can be applied to vulnerable watersheds in arid and semi-arid regions. It can help policymakers to integrate additional sustainable solutions into construction dams and their implementation in development plans.
Riparian zones with their buffering ability and abundant water supply are often subjected to intensive agricultural activities. We investigated a riparian aquifer located near a stream in South Korea that recently experienced sharply decreasing groundwater levels and elevated nitrate (NO3–) concentrations, which were attributed to local agricultural activities. Our goal was to identify the predominant nitrogen sources and NO3– removal processes. Multiple approaches including geochemical and isotopic tracers, land-use analysis, metabolic gene quantification, and inert gas tracers were used to elucidate groundwater and nutrient dynamics in stream-side granitic aquifers. The dual isotopic composition of NO3– identified manure and sewage as the major sources of NO3– contamination. Denitrification was the dominant NO3– removal process in the aquifer, as demonstrated by the negative relationship between δ¹⁵N and δ¹⁸O values in NO3–and NO3–/Cl–. Denitrification and anammox genes were also observed in microbial communities of the aquifer throughout the study site, suggesting that these processes support effective natural NO3– attenuation in groundwater. A mixing model constructed using a catchment-scale dataset including SiO2 concentrations and δ¹⁸O-H2O suggested that mixing with paddy soil water was the major driver of denitrification in the aquifer at the study site, where impervious layers provided anaerobic conditions for natural NO3– attenuation. Denitrification reduced the NO3– flux into the nearby stream by up to 114.4 NO3– kg/ha/y (26 kg N/ha/y). The N2 generated by denitrification did not accumulate in the groundwater, but mostly escaped from groundwater to the atmosphere, as demonstrated by the degassed signature of dissolved inert gases below the air saturated water level. This study identified the predominant NO3– sources and conceptualized N cycling in the heavily developed agricultural riparian aquifer using multiple tracers, demonstrating that NO3– is partially removed through denitrification and possibly anammox while N2 mostly escapes into the atmosphere.
Groundwater is a major source of water supply in Kericho County, Kenya. However, this water source is threatened by the rise in the human population and climate change. Under these conditions, it is crucial to assess the sustainability of the groundwater resource in Kericho County. Thus, this study aimed to investigate the potential of groundwater in Kericho County, Kenya. Groundwater Modelling System (GMS) software was used to develop a conceptual model to aid in the assessment of groundwater. Results from calibration showed hydraulic conductivity values varying from 0.279 to 1.12 m/d, while the recharge rates ranged from 0.5 to 0.00022 m/d. Also, a predictive run was conducted in the calibrated model to examine the aquifer's response to abstractions under three different scenarios. Scenario 1 assessed the impacts of population growth on groundwater resources; scenario 2 evaluated the effects of climate change on groundwater; scenario 3 assessed the effect of population growth and climate change on groundwater in the study area. The results showed that excessive pumping rates interfere with the surface water and groundwater interactions. There was slight decline in constant head for location near the river. However, the recharge rate was higher than the abstraction, indicating that groundwater will remain sustainable as the primary source of water supply for the residents. In conclusion, the volumetric budget for the three scenarios shows that the aquifer has sufficient water supply to be used by the population despite the effects of climate change and population growth. Despite the availability of adequate water supply from the aquifer, there is a need for an effective and sustainable use of water from the aquifer, especially in the face of climate change and population increase.
Nagavali is one of the important east flowing river basins, providing a water source for more than 5 million people for various applications in two south Indian states namely Orissa and Andhra Pradesh. During the last two decades, the expansion and intensification of agriculture have increased through the development of various surface water storage projects to support agriculture development. In this scenario, understanding the complete water balance under different land use and climate is required for the sustainable management of water resources and agriculture development. The present study attempted to quantify integrated hydrological processes under changing land use and climate over three decades from 1985 to 2018 with the help of coupled SWAT-MODFLOW. The study quantified the river-aquifer interactions and dynamic groundwater recharge by implementing dynamic land use and climate in the coupled hydrological model for three decades. The integrated model has revealed that the combined impact of land use change and climate has increased runoff by 26%, percolation by 16%, irrigation water requirement by 48%, and groundwater storage has declined by 20%, by the end of 2018 when compared to 1991. The present study emphasized the need of modelling surface–groundwater in an integrated manner for better understating hydrological processes to support sustainable water resource management.
The healthy and sustainable development of irrigation area not only serves as the guarantee of national food production security, but also shoulders the important task of regional ecological security, in which maintaining groundwater level plays an important role. Due to the close relationship between groundwater level and irrigation recharge groundwater, realizing rational use of water resources under strictly implementing the total limit of water use and holding reasonable groundwater level is of great significance to the healthy development of irrigated areas. Therefore, this study established a spatial-temporal optimal allocation regulation method of irrigation water resources by coupling groundwater numerical technology and the characteristics of hydrological cycle with comprehensively considering the dual constraints between total water consumption and reasonable groundwater depth. Besides, taking Helan County, a typical area of Qingtongxia Irrigation district in Ningxia as an example, a case study on optimal allocation of irrigation water resources was carried out. The results show that compared with the actual current water use situation, the total irrigation water shortage rate of Helan County Irrigation District (HCID) decreases from 21.61% to 21%. Under the combined control of total available water and groundwater depths, it is realized the fairness and balance of water use in different regions and periods by the allocation of water resources in spatial and temporal. Meanwhile, the area located in the reasonable groundwater depth range increased by 1.65% after optimization. Overall, the balanced and optimal allocation method of irrigation water resources with both total water use and groundwater depth control is not only improving the efficient and rational utilization of limited water resources, but also can regulate groundwater depth to guarantee regional ecological health and sustainable development.
The present study engages two powerful models viz., Soil and Water Assessment Tool (SWAT) and Groundwater Modeling System (GMS) to simulate groundwater and surface water conditions to aid conjunctive use applications. This work elaborates a robust coupling of these two models for conjunctive use studies. The study area, Khatav in Maharashtra, is mostly drought-prone, semi-arid and has an average annual rainfall of about 560 mm. In order to have a sustainable and efficient water resource management in this semi-arid region, conjunctive use of groundwater and surface water is essential. Therefore, the SWAT and GMS models were calibrated and validated by using observed data for a period of twelve years, from 2000 to 2012. The basin area considered for the study purpose is 470 km2. After the SWAT model has been processed, study area was divided into 51 hydrological response units (HRUs) and 5 sub-basins. The methodology used in this work was, the Soil Conservation Service (SCS) curve number was used to estimate surface runoff. As the SWAT model cannot be used to predict groundwater levels in the basin, the Groundwater Modeling System (GMS) has been used to model the groundwater processes. The sensitivity of work was assessed by using SWAT-CUP tool and with SUFI-2 algorithm. The results showed that the average annual flow from the basin is 3.059 × 103 m3 and average curve number is 87.43. The study recommends recharging of the wells which are already available in the basin by operating them continuously to induce recharging by available surface water. The simulation shows that altogether due to reduction in evaporation and surface absorption, the groundwater level in basin is raised by 0.6 m. The validity of the simulations and acceptance of the SWAT model for the present study has been confirmed by values of RSR (0.60) and NSE (0.82) parameters.KeywordsSurface waterGroundwaterConjunctive useSWATGMS
The interaction between surface water and groundwater constitutes a critical process to understand the quantitative and qualitative regime of dependent hydrosystems. A multi-scale approach combining cross-disciplinary techniques can considerably reduce uncertainties and provide an optimal understanding of groundwater and surface water exchanges. The simulation process constitutes the most effective tool for such analysis; however, its implementation requires a variety of data, a detailed analysis of the hydrosystem, and time to finalize a reliable solution. The results of the simulation process contribute to the raising of awareness for water protection and the application of better management strategies. Knowledge of models' parameters has great importance to ensure reliable results in the modeling process. In this study, a literature overview of modeling applications in groundwater – surface water interaction is provided. In this context, a comprehensive and holistic approach to groundwater and surface water simulation codes is here presented; results, case studies, and future challenges are also discussed. The main finding of the analysis highlights uncertainties and gaps in the modeling process due to the lack of high frequency and depth dependent field measurements. In many studies, authors underestimate the importance of the hydrogeological regime, and the discretization of hydraulic parameters is often lumped in a simplified manner. The modeling ethics in terms of data transparency and openness should be widely considered to improve the modeling results. The current study contributes to overcome common weaknesses of model applications, fulfils gaps in the existing literature, and highlights the importance of the modeling process in planning sustainable management of water resources.
The importance of considering groundwater (GW) and surface water (SW) as a single resource of two interconnected components has rapidly increased during the last decades. To investigate GW-SW interaction in an aquifer system exploited by several pumping wells, an integrated continuous monitoring of the hydrological conditions was carried out. The sub-catchment (14 km2), located in the Aspio basin near Ancona (Central Italy), is drained by a small stream named Betelico, and it is characterised by the presence of an unconfined alluvial aquifer and a semi-confined limestone aquifer. The aim of this study is to evaluate the drivers of stream drying up occurred during the last couple of years. This has been achieved by applying a trend analysis on rainfall, air temperatures, piezometric and stream level, and well pumping rates. Precipitation trends were analysed over a 30-years period through the calculation of the Standard Precipitation Index (SPI) and through heavy rainfall events frequency plots, while the correlation between piezometric stream levels and pumping rate was analysed during the last six years. The groundwater level was compared with the stream baseflow level, highlighting the interconnection between GW-SW over the years. The analysis on the water surplus (WS) trend, together with the rainfall events characterisation, supports the hypothesis of the decrease in recharge rate as the main driver of the stream drying up. This case study stresses the importance of studying GW-SW interactions in a continuously changing climatic context characterised by a decreasing precipitation trend, coupling both the advantages of a robust method like trend analysis on time series and the field continuous monitoring.
This study aimed to evaluate the degree of groundwater pollution and to assess the contribution of specific ionic sources to groundwater, thereby helping to identify the changes in groundwater chemistry and also in groundwater quality from a rural part of Telangana, India, using the comprehensive understanding of geochemical ratios (GR), pollution index of groundwater (PIG), unmix model (UM), and land use/land cover. Groundwater samples collected (22) from the study area were analysed for pH, EC, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO3⁻, Cl⁻, SO4²⁻, NO3⁻, and F⁻. The hydrogeochemical diagram showed the dominant groundwater type of Ca²⁺- Mg²⁺- HCO3⁻ due to the water-soil-rock interactions. GR, chloro-alkaline indices, and saturation indices revealed the groundwater chemistry that explains the mineral weathering and dissolution, ion exchange, and evaporation processes as the chief geogenic origin, and also the contamination of surface water due to the influence of household wastewater, septic tank leaks, irrigation-return-flows, chemical composts, etc. as the secondary anthropogenic sources on the aquifer system. Changes in groundwater quality from the recharge area to the discharge area and the correlation coefficient of chemical variables further supported the sources of geogenic and anthropogenic origins. According to PIG's calculations, the present study area was classified as the insignificant pollution zone (5.89%), which shows all chemical variables within their drinking water quality limits, and the low pollution zone (43.34%), medium pollution zone (27.48%), high pollution zone (17.34%), and very high pollution zone (5.95%), which exhibit the TDS, Mg²⁺, Na⁺, K⁺, HCO3⁻, Cl⁻, NO3⁻, SO4²⁻, and F⁻contents above the drinking water quality standards. This indicates the gradual increase in the intensity of pollution activity. UM also classified the contribution of specific ions (>50%) into three sources: Source I (K⁺) measures the poor sewage conditions and potash fertilizers; Source II (SO4²⁻, Mg²⁺, NO3⁻, Na⁺, and Ca²⁺) specifies the poor sewage conditions, irrigation-return-flows, and chemical fertilizers (gypsum and nitrate); and Source III (F−and HCO3⁻) represents the dissolution of fluoride minerals as a major contributor to groundwater chemistry. Furthermore, the land use/land cover observations had also supported the assessment of groundwater pollution levels and the contribution of specific ionic sources made by PIG and UM. As a result, the present study clearly indicated that groundwater quality of a geogenic origin is primarily overcome the impact of anthropogenic sources. Therefore, the present study suggested strategic measures to control groundwater pollution and improve groundwater quality.
Addressing modern water management challenges requires the integration of physical, environmental and socio-economic aspects, including diverse stakeholders’ values, interests and goals. Early stakeholder involvement increases the likelihood of acceptance and legitimacy of potential solutions to these challenges. Participatory modelling allows stakeholders to co-design solutions, thus facilitating knowledge co-construction/social learning. In this work, we combine integrated modelling and participatory modelling to develop and deploy a digital platform supporting decision-making for water management in a semiarid basin under contentious water use. The purpose of this tool is exploring “on-the-fly” alternative water management strategies and potential policy pathways with stakeholders. We first co-designed specific water management strategies/impact indicators and collected local knowledge about farmers’ behaviour regarding groundwater regulation. Second, we coupled a node–link water balance model, a groundwater model and an agent-based model in a digital platform (SimCopiapo) for scenario exploration. This was done with constant input from key stakeholders through a participatory process. Our results suggest that reductions of groundwater demand (40%) alone are not sufficient to capture stakeholders’ interests and steer the system towards sustainable water use, and thus a portfolio of management strategies including exchanges of water rights, improvements to hydraulic infrastructure and robust enforcement policies is required. The establishment of an efficient enforcement policy to monitor compliance on caps imposed on groundwater use and sanction those breaching this regulation is required to trigger the minimum momentum for policy acceptance. Finally, the participatory modelling process led to the definition of a diverse collection of strategies/impact indicators, which are reflections of the stakeholders’ interests. This indicates that not only the final product—i.e., SimCopiapo—is of value but also the process leading to its creation.
Global water demand has increased dramatically due to rapid population growth in recent decades. For arid and semi-arid countries like Iran, water supply has become a major concern. Management of water resources was previously focused on surface water (SW) or groundwater (GW) individually (Winter et al., 1998). However, SW and GW are components of the hydrological cycle that interact with each other (Deb et al., 2019). The SW bodies like streams, rivers, reservoirs, and wetlands are in direct or indirect interaction with GW (Eini et al., 2019). Therefore, effective water management requires a comprehensive understanding of SW-GW interactions. However, we have limited knowledge about SW-GW interactions because of the lack of available field measurement/data and complexities associated with SW, GW and SW-GW processes. Thus, SW-GW interactions have frequently been ignored. Lack of proper quantification of SW-GW interactions in water resources management has resulted in unrealistic outputs and therefore, unsuitable policies and decisions (e.g. Aliyari et al., 2019; Dehghanipour et al., 2019; Pai, 2015; Tian et al., 2015; Pérez-Martín et al., 2014; Cho et al., 2010). Integrated simulation of the whole water cycle is required for realistically simulating exchange between SW and GW (Guzman et al., 2015).
It is imperative to understand the interconnectedness of water use and hydrological impacts for water policy design underlying varying hydrological conditions across space and over time. However, such analysis remains difficult, constrained by the lack of appropriate modeling tools that fully integrate water policies, water use, and hydrological processes with high spatiotemporal resolutions. To address this challenge, this study proposes a distributed policy design scheme featuring spatially variable and temporally dynamic policies for conjunctive surface water‐groundwater management in large river basins. A fully integrated modeling framework is developed to tightly couple (a) an agent‐based model for farmers' water use under distributed water policies and (b) a physically based hydrological model for surface water‐groundwater processes. The modeling framework is applied to the Heihe River Basin to assess water use and hydrological impacts under distributed water policies. By using the distributed policy scheme to adjust a water policy (e.g., groundwater tax) across space and over time, we found that hydrological outcomes can be improved without adversely reducing agricultural water supply. For example, by shifting the implementation of a high groundwater tax from dry to wet years, a rise of the water table by 0.28 m (0.03–0.95 m across different irrigation districts) can be achieved while the total water supply is maintained at a similar level. Furthermore, hydrological externality effects among nearby districts can be explicitly identified and quantified based on assessments of spatially varying water policies. This study highlights the need for water policy design to consider spatiotemporal variations in the physical hydrological system.
The behavior of groundwater response to leakage of surface water in the middle reaches area of Heihe River Basin is significantly influenced by a thick vadose zone. The groundwater regime is a result of two recharge events due to leakage of Heihe River and irrigation water with different delay time. A nonlinear leakage model is developed to calculate the monthly leakage of Heihe River in considering changes of streamflow, river stage and agricultural water utilization. Numerical modeling of variable saturated flow is carried out to investigate the general behaviors of leakage-recharge conversion through a thick vadose zone. It is found that the recharge pattern can be approximated by simple reservoir models of leakages under a river and under an irrigation district with different delay-time and recession coefficient. A triple-reservoir model of relationship between surface water, vadose zone and groundwater is developed. It reproduces the groundwater regime during 1989–2006 with variable streamflow of Heihe River and agricultural water utilization. The model is applied to interpret changes of groundwater level during 2007–2008 that observed in the Watershed Airborne Telemetry Experimental Research (WATER).
Gujarat state in Western India exemplifies all challenges of an agrarian economy founded on groundwater overexploitation sustained over decades by perverse energy subsidies. Major consequences are: secular decline in groundwater levels, deterioration of groundwater quality, rising energy cost of pumping, soaring carbon footprint of agriculture and growing financial burden of energy subsidies. In 2009, Government of Gujarat asked the present author, an economist, to chair a Taskforce of senior hydro-geologists and civil engineers to develop and recommend a Managed Aquifer Recharge (MAR) strategy for the state. This paper summarizes the recommended strategy and its underlying logic. It also describes the imperfect fusion of socio-economic and hydro-geologic perspectives that occurred in course of the working of the Taskforce and highlights the need for trans-disciplinary perspectives on groundwater governance.
Percolation of precipitation through unsaturated zones is important for recharge of ground water. Rain and snowmelt at land surface are partitioned into different pathways including runoff, infiltration, evapotranspiration, unsaturated-zone storage, and recharge. A new package for MODFLOW-2005 called the Unsaturated-Zone Flow (UZF1) Package was developed to simulate water flow and storage in the unsaturated zone and to partition flow into evapotranspiration and recharge. The package also accounts for land surface runoff to streams and lakes.
A kinematic wave approximation to Richards’ equation is solved by the method of characteristics to simulate vertical unsaturated flow. The approach assumes that unsaturated flow occurs in response to gravity potential gradients only and ignores negative potential gradients; the approach further assumes uniform hydraulic properties in the unsaturated zone for each vertical column of model cells. The Brooks-Corey function is used to define the relation between unsaturated hydraulic conductivity and water content. Variables used by the UZF1 Package include initial and saturated water contents, saturated vertical hydraulic conductivity, and an exponent in the Brooks-Corey function. Residual water content is calculated internally by the UZF1 Package on the basis of the difference between saturated water content and specific yield.
The UZF1 Package is a substitution for the Recharge and Evapotranspiration Packages of MODFLOW-2005. The UZF1 Package differs from the Recharge Package in that an infiltration rate is applied at land surface instead of a specified recharge rate directly to ground water. The applied infiltration rate is further limited by the saturated vertical hydraulic conductivity. The UZF1 Package differs from the Evapotranspiration Package in that evapotranspiration losses are first removed from the unsaturated zone above the evapotranspiration extinction depth, and if the demand is not met, water can be removed directly from ground water whenever the depth to ground water is less than the extinction depth. The UZF1 Package also differs from the Evapotranspiration Package in that water is discharged directly to land surface whenever the altitude of the water table exceeds land surface. Water that is discharged to land surface, as well as applied infiltration in excess of the saturated vertical hydraulic conductivity, may be routed directly as inflow to specified streams or lakes if these packages are active; otherwise, this water is removed from the model.
The UZF1 Package was tested against the U.S. Geological Survey’s Variably-Saturated Two-Dimensional Flow and Transport Model for a vertical unsaturated flow problem that includes evapotranspiration losses. This report also includes an example in which MODFLOW-2005 with the UZF1 Package was used to simulate a realistic surface-water/ground-water flow problem that includes time and space variable infiltration, evapotranspiration, runoff, and ground-water discharge to land surface and to streams. Another simpler problem is presented so that the user may use the input files as templates for new problems and to verify proper code installation.
Surface–groundwater (SW–GW) interactions constitute a critical proportion of the surface and groundwater balance especially during dry conditions. Conjunctive management of surface and groundwater requires an explicit account of the exchange flux between surface and groundwater when modelling the two systems. This paper presents a case study in the predominantly gaining Boggabri–Narrabri reach of the Namoi River located in eastern Australia. The first component of the study uses the Upper Namoi numerical groundwater model to demonstrate the importance of incorporating SW–GW interactions into river management models. The second component demonstrates the advantages of incorporating groundwater processes in the Namoi River model.
The EPA Storm Water Management Model (SWMM) is a widely used program for simulating urban runoff quantity and quality. Its existing documentation includes a User's Manual that describes how to run the program and a Reference Manual that covers its theory and algorithms. A new manual, the ''SWMM Applications Manual'', has been added to this collection. It contains nine worked-out examples addressing common stormwater management and design problems encountered in practice. The manual will be especially useful for new SWMM users who need additional guidance in applying this powerful tool to urban drainage design and analysis.
Recent observations show that the river Zenne (Belgium) remains well below the water quality goals stated by the European Union Water Framework Directive. An interuniversity, multidisciplinary research project was therefore launched to evaluate the effects of wastewater management plans on the ecological functioning of the river. To this end, different water quantity and quality processes had to be considered and modelled, e.g., the hydrology in the river basin, hydraulics in the river and sewers, erosion and sediment transport, faecal bacteria transport and decay. This paper considers the development of an Open Modelling Interface (OpenMI) based integrated model for the purpose of simulating the river's sediment dynamics. We used the Soil and Water Assessment Tool (SWAT) to model water and sediment fluxes from rural areas. The Storm Water Management Model (SWMM) was used to simulate the hydraulics of the river, canal, and sewer systems in urban catchments. New model codes for sediment transport and stream water temperature were developed to complement SWMM. The results show that the integrated sediment transport model reproduced the sediment concentrations in the river Zenne with ‘good’ to ‘satisfactory’ accuracy. We may therefore conclude that the OpenMI has been successfully implemented to integrate water quality models into a hydraulic one. While the OpenMI run-time data communication inflicted calculation time overhead, we found that the overhead was not significant with respect to the total run-time of the integrated model.
Previous studies indicate predominantly increasing trends in precipitation across the Western United States, while at the same time, historical streamflow records indicate decreasing summertime streamflow and 25th percentile annual flows. These opposing trends could be viewed as paradoxical, given that several studies suggest that increased annual precipitation will equate to increased annual groundwater recharge, and therefore increased summertime flow. To gain insight on mechanisms behind these potential changes, we rely on a calibrated, integrated surface and groundwater model to simulate climate impacts on surface water/groundwater interactions using 12 general circulation model projections of temperature and precipitation from 2010 to 2100, and evaluate the interplay between snowmelt timing and other hydrologic variables, including streamflow, groundwater recharge, storage, groundwater discharge, and evapotranspiration. Hydrologic simulations show that the timing of peak groundwater discharge to the stream is inversely correlated to snowmelt runoff and groundwater recharge due to the bank storage effect and reversal of hydraulic gradients between the stream and underlying groundwater. That is, groundwater flow to streams peaks following the decrease in stream depth caused by snowmelt recession, and the shift in snowmelt causes a corresponding shift in groundwater discharge to streams. Our results show that groundwater discharge to streams is depleted during the summer due to earlier drainage of shallow aquifers adjacent to streams even if projected annual precipitation and groundwater recharge increases. These projected changes in surface water/groundwater interactions result in more than a 30% decrease in the projected ensemble summertime streamflow. Our findings clarify causality of observed decreasing summertime flow, highlight important aspects of potential climate change impacts on groundwater resources, and underscore the need for integrated hydrologic models in climate change studies.
A method is presented for estimating seepage loss and streambed hydraulic conductivity along intermittent and ephemeral streams using streamflow front velocities in initially dry channels. The method uses the kinematic wave equation for routing streamflow in channels coupled to Philip's equation for infiltration. The coupled model considers variations in seepage loss both across and along the channel. Water redistribution in the unsaturated zone is also represented in the model. Sensitivity of the streamflow front velocity to parameters used for calculating seepage loss and for routing streamflow shows that the streambed hydraulic conductivity has the greatest sensitivity for moderate to large seepage loss rates. Channel roughness, geometry, and slope are most important for low seepage loss rates; however, streambed hydraulic conductivity is still important for values greater than 0.008 m/d. Two example applications are presented to demonstrate the utility of the method.
Groundwater discharge constitutes a significant proportion of the total flow volume in most rivers. The exchange flux between surface and groundwater greatly impacts the surface as well as the groundwater balance with serious implications on ecosystem health especially during low flow conditions. There is a move towards conjunctive river–aquifer management with the integration of surface–groundwater exchange fluxes into surface and groundwater models to manage water as a single resource. Groundwater–Surface water (GW–SW) exchange fluxes are seldom integrated into river operation and planning models. The time lags associated with the impacts of groundwater processes on nearby rivers can greatly compromise the forecasting capacity of river models especially during low flow conditions.
Questions about the importance of conduit geometry and about the values of hydraulic parameters in controlling ground-water flow and solute transport through karstic aquifers have remained largely speculative. One goal of this project was to assess the role that the conduit geometry and the hydraulic parameters have on controlling transport dynamics within karstic aquifers. The storm water management model (SWMM) was applied to the Devil’s Icebox–Connor’s Cave System in central Missouri, USA. Simulations with incremental changes to conduit geometry or hydraulic parameters were performed with the output compared to a calibrated baseline model. Ten percent changes in the length or width of a conduit produced statistically significant different fluid flow responses. The model exhibited minimal sensitivity to slope and infiltration rates; however, slight changes in Manning’s roughness coefficient can highly alter the simulated output.
Traditionally, the difference in flow dynamics between karstified aquifers and porous media aquifers has led to the idea that modeling of karst aquifers is more difficult and less precise than modeling of porous media aquifers. When evaluated against models for porous media aquifers, SWMM produced results that were as accurate (10% error compared to basecase). In addition, SWMM has the advantage of providing data about local flow. While SWMM may be an appropriate modeling technique for some karstic aquifers, SWMM should not be viewed as a universal solution to modeling karst systems.
Accurate determination of reference evapotranspiration is very essential for precise computation of crop water use. Several models have been used in computing reference evapotranspiration and they require local calibration in order to validate their usage. Climatic data used in computing reference evapotranspiration (ET o) for Abeokuta, Ijebu-Ode and Itoikin were obtained from Ogun-Osun River Basin and Rural Development Authourity, Abeokuta, Nigeria. For Abeokuta, complete climatic data were used in the computation of the ET o while limited climatic data were used in computing ET o for Ijebu-Ode and Itoikin using FAO-56 Penman-Monteith (FAO-56 PM), Jensen-Haise and Hargreaves models. In Abeokuta, the average coefficients of determination R 2 obtained when ET o computed using Jensen-Haise and Hargreaves models were compared with FAO-56 PM model were 0.7914 and 0.5158 respectively. The average Root Mean Square Errors (RMSEs) obtained between Jensen-Haise, Hargreaves and FAO-56 PM models were 1.03 and 1.79 mmd -1 respectively. The index of agreement between pan evaporation and FAO-56 PM, Jensen-Haise and Hargreaves models were 0.56, 0.71 and 0.52 respectively. The average R 2 of the ET o computed using s R and temperature for FAO-56 PM and Jensen-Haise were 0.6784 and 0.8488 respectively. For Ijebu-Ode, the average R 2 when Jensen-Haise, Hargreaves were compared with FAO-56 PM model were 0.9908, 0.9907 respectively. The average RMSEs between FAO-56 PM, Jensen-Haise and Hargreaves were 2.51 and 0.87 mmd -1 respectively while the index of agreement between FAO-56 PM, Jensen-Haise and Hargreaves models were 0.49, 0.88 and 0.54 respectively. Similarly for Itoikin, the average R 2 obtained when Jensen-Haise and Hargreaves model were compared with FAO-56 PM were 0.9754 and 0.9557 respectively. The average RMSEs obtained between FAO-56 PM and Jensen-Haise and Hargreaves models were 2.50 and 0.89 mmd -1 respectively while the index of agreement between pan evaporation and FAO-56PM, Jensen-Haise and Hargreaves models were 0.28, 0.61 and 0.34 respectively. It is hereby recommended that beside FAO-56PM model, Jensen-Haise model is also recommended for the computation of ET o in situations where only maximum and minimum temperatures are available in Ogun-Osun River basin.
Aim Many macroecological analyses are based on analyses of climatological data, within which evapotranspiration estimates are of central importance. In this paper we evaluate and review the use of evapotranspiration models and data in studies of geographical ecology to test the likely sensitivity of the analyses to variation in the performance of different metrics of potential evapotranspiration.
Location Analyses are based on: (1) a latitudinal transect of sites (FLUXNET) for 11 different land-cover types; and (2) globally gridded data.
Methods First, we review the fundamental concepts of evapotranspiration, outline basic evapotranspiration models and describe methods with which to measure evapotranspiration. Next, we compare three different types of potential evapotranspiration models – a temperature-based (Thornthwaite type), a radiation-based (Priestley–Taylor) and a combination (Penman–Monteith) model – for 11 different land-cover types. Finally, we compare these models at continental and global scales.
Results At some sites the models differ by less than 7%, but generally the difference was greater than 25% across most sites. The temperature-based model estimated 20–30% less than the radiation-based and combination models averaged across all sites. The combination model often gave the highest estimates (22% higher than the radiation-based model averaged across all sites). For continental and global averages, the potential evapotranspiration was very similar across all models. However, the difference in individual pixels was often larger than 150 mm year−1 between models.
Main conclusions The choice of evapotranspiration model and input data is likely to have a bearing on model fits and predictions when used in analyses of species richness and related phenomena at geographical scales of analysis. To assist those undertaking such analyses, we provide a guide to selecting an appropriate evapotranspiration model.
Ecological constraints in subsurface environments relate directly to groundwater flow, hydraulic conductivity, interstitial biogeochemistry, pore size, and hydrological linkages to adjacent aquifers and surface ecosystems. Groundwater ecology has evolved from a science describing the unique subterranean biota to its current form emphasising multidisciplinary studies that integrate hydrogeology and ecology. This multidisciplinary approach seeks to elucidate the function of groundwater ecosystems and their roles in maintaining subterranean and surface water quality. In aquifer-surface water ecotones, geochemical gradients and microbial biofilms mediate transformations of water chemistry. Subsurface fauna (stygofauna) graze biofilms, alter interstitial pore size through their movement, and physically transport material through the groundwater environment. Further, changes in their populations provide signals of declining water quality. Better integrating groundwater ecology, biogeochemistry, and hydrogeology will significantly advance our understanding of subterranean ecosystems, especially in terms of bioremediation of contaminated groundwaters, maintenance or improvement of surface water quality in groundwater-dependent ecosystems, and improved protection of groundwater habitats during the extraction of natural resources. Overall, this will lead to a better understanding of the implications of groundwater hydrology and aquifer geology to distributions of subsurface fauna and microbiota, ecological processes such as carbon cycling, and sustainable groundwater management.
Quasi three-dimensional (quasi-3D)modelling plays a major role in analysis of groundwater flow in multiaquifer systems and it can be an efficient tool for artificial recharge modelling. As the role of artificial recharge in groundwater management continues to increase, analysis of responses to artificial recharge has a particular significance. This paper deals with some practical aspects of the development of a general quasi-3D model based on an algorithm employing the combined techniques of Finite Element Method (FEM) and convolution integral. Responses to well recharge in a multiaquifer system were analyzed. The results of flow and consolidation analyses for an idealized hydrogeological section of the Bangkok aquifer system are presented to illustrate the role of artificial recharge in land subsidence control for Bangkok city. Here, land subsidence due to groundwater extraction is a serious issue to be resolved, and artificial recharge has been recommended as a supplemental means of mitigation.
The interactions between groundwater and surface water are complex. To understand these interactions in relation to climate, landform, geology, and biotic factors, a sound hydrogeoecological framework is needed. All these aspects are synthesized and exemplified in this overview. In addition, the mechanisms of interactions between groundwater and surface water (GW–SW) as they affect recharge–discharge processes are comprehensively outlined, and the ecological significance and the human impacts of such interactions are emphasized. Surface-water and groundwater ecosystems are viewed as linked components of a hydrologic continuum leading to related sustainability issues. This overview concludes with a discussion of research needs and challenges facing this evolving field. The biogeochemical processes within the upper few centimeters of sediments beneath nearly all surface-water bodies (hyporheic zone) have a profound effect on the chemistry of the water interchange, and here is where most of the recent research has been focusing. However, to advance conceptual and other modeling of GW–SW systems, a broader perspective of such interactions across and between surface-water bodies is needed, including multidimensional analyses, interface hydraulic characterization and spatial variability, site-to-region regionalization approaches, as well as cross-disciplinary collaborations.
A major research plan entitled Integrated research on the ecohydrological process of the Heihe River Basin was launched by the National Natural Science Foundation of China in 2010. One of the key aims of this research plan is to establish a research platform that integrates observation, data management, and model simulation to foster twenty-first-century watershed science in China. Based on the diverse needs of interdisciplinary studies within this research plan, a program called the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) was implemented. The overall objective of HiWATER is to improve the observability of hydrological and ecological processes, to build a world-class watershed observing system, and to enhance the applicability of remote sensing in integrated ecohydrological studies and water resource management at the basin scale. This paper introduces the background, scientific objectives, and experimental design of HiWATER. The instrumental setting and airborne mission plans are also outlined. The highlights are the use of a flux observing matrix and an eco-hydrological wireless sensor network to capture multiscale heterogeneities and to address complex problems, such as heterogeneity, scaling, uncertainty, and closing water cycle at the watershed scale. HiWATER was formally initialized in May 2012 and will last four years until 2015. Data will be made available to the scientific community via the Environmental and Ecological Science Data Center for West China. International scientists are welcome to participate in the field campaign and use the data in their analyses.
Rivers and aquifers are, in many cases, a connected resource and as such the interactions between them need to be understood and quantified for the resource to be managed appropriately. The objective of this paper is to advance the understanding of river–aquifer interactions processes in semi-arid environments stressed by groundwater abstraction. This is performed using data from a specific catchment where records of precipitation, evapotranspiration, river flow, groundwater levels and groundwater abstraction are analysed using basic statistics, hydrograph analysis and a simple mathematical model to determine the processes causing the spatial and temporal changes in river–aquifer interactions. This combined approach provides a novel but simple methodology to analyse river–aquifer interactions, which can be applied to catchments worldwide. The analysis revealed that the groundwater levels have declined (~ 3 m) since the onset of groundwater abstraction. The decline is predominantly due to the abstraction rather than climatic changes (r = 0.84 for the relationship between groundwater abstraction and groundwater levels; r = 0.92 for the relationship between decline in groundwater levels and magnitude of seasonal drawdown). It is then demonstrated that, since the onset of abstraction, the river has changed from being gaining to losing during low-flow periods, defined as periods with flow less than 0.5, 1.0 or 1.5 GL/day (1 GL/day = 1 × 106 m3/day). If defined as 10 years) between the onset of groundwater abstraction and the changeover from gaining to losing conditions. Finally, a relationship between the groundwater gradient towards the river and the river flow at low-flow is demonstrated. The results have important implications for water management as well as water ecology and quality. Copyright © 2012 John Wiley & Sons, Ltd.
Pressure on limited water resources and the environment requires better understanding of how landscape change impacts river flow. Rainfall-runoff models have traditionally focused on estimating total river flows with less emphasis on modelling the groundwater component or the consequences of different land-use change scenarios. In this paper, we present the GWlag model, a water-generation model that predicts river flows with explicit accounting of the impacts of catchment land-use change and surface–groundwater interactions. The paper firstly describes the theory that underpins the model and its calibration then presents a case study application in the Tarcutta Creek catchment of the Murray–Darling Basin, Australia. The case study aims at: (i) demonstrating the ability of the model to predict daily river flows; (ii) modelling the impacts of hypothetical plantation forestry expansions on river flows; and (iii) showing the impacts of reduced recharge on the low-flow regime using three indices, namely, Q90/Q50 (where Qn refers to nth percentile flow), slope of low-flow part of flow duration curve, and % of zero-flow days. Results showed that predicted flows agreed favourably to those observed at the gauge especially during low-flow conditions. The hypothetical plantation expansion from 32% to 87% of the catchment area has resulted in reductions of 48% and 32%, in Q50 and Q20, respectively. The low-flow indices demonstrated the great sensitivity of low flow to reductions in recharge with the trend of the low-flow response changing to non-linear for recharge reductions beyond 10%. GWlag daily river flow predictions compared favourably to those obtained from four other rainfall-runoff models in terms of the Nash–Sutcliffe model efficiency (E). However, GWlag produced the highest E-value for log-transformed flows thus highlighting the model's superior predictive capability during low-flow conditions.
Management of regulated water systems has become increasingly complex due to rapid socio-economic growth and environmental changes in river basins over recent decades. This paper introduces the Source Integrated Modelling System (IMS), and describes the individual modelling components and how they are integrated within it. It also describes the methods employed for tracking and assessment of uncertainties, as well as presenting outcomes of two case study applications.Traditionally, the mathematical tools for water resources planning and management were generally designed for sectoral applications with, for example, groundwater being modelled separately from surface water. With the increasing complexity of water resources management in the 21st century those tools are becoming outmoded. Water management organisations are increasingly looking for new generation tools that allow integration across domains to assist their decision making processes for short-term operations and long-term planning; not only to meet current needs, but those of the future as well.In response to the need for an integrated tool in the water industry in Australia, the eWater Cooperative Research Centre (CRC) has developed a new generation software package called the Source IMS. The Source IMS is an integrated modelling environment containing algorithms and approaches that allow defensible predictions of water flow and constituents from catchment sources to river outlets at the sea. It is designed and developed to provide a transparent, robust and repeatable approach to underpin a wide range of water planning and management purposes. It can be used to develop water sharing plans and underpin daily river operations, as well as be used for assessments on water quantity and quality due to changes in: i) land-use and climate; ii) demands (irrigation, urban, ecological); iii) infrastructure, such as weirs and reservoirs; iv) management rules that might be associated with these; and v) the impacts of all of the above on various ecological indices. The Source IMS integrates the existing knowledge and modelling capabilities used by different state and federal water agencies across Australia and has additional functionality required for the river system models that will underpin the next round of water sharing plans in the country. It is built in a flexible modelling environment to allow stakeholders to incorporate new scientific knowledge and modelling methods as they evolve, and is designed as a generic tool suitable for use across different jurisdictions. Due to its structure, the platform can be extended/customised for use in other countries and basins, particularly where there are boundary issues.
For approximately 20 years, there has been a concerted effort, by several different research groups, to simulate observed rainfall-runoff events from the well-known R-5 catchment, located near Chickasha, Oklahoma. These prior simulation efforts, with relatively simple models of Horton-type overland flow, have not been entirely successful, as the streamflow generation process for the R-5 catchment, as now recognized, may not be totally dominated by the Horton mechanism. In the effort reported here, a new fully coupled comprehensive physics-based hydrologic-response model, the Integrated Hydrology Model (InHM), is tested for two R-5 rainfall-runoff events. The InHM simulations in this study clearly show, in a hypothesis-testing mode, that both the Horton and Dunne overland flow mechanisms can be important streamflow generation processes for R-5 events. The InHM simulations reported here also suggest that accurate accounting of soil water storage can be as important as exhaustive characterization of spatial variations in near-surface permeability.
Estimating surface evapotranspiration is extremely important for the study of water resources in arid regions. Data from the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer (NOAA/AVHRR), meteorological observations and data obtained from the Watershed Allied Telemetry Experimental Research (WATER) project in 2008 are applied to the evaporative fraction model to estimate evapotranspiration over the Heihe River Basin. The calculation method for the parameters used in the model and the evapotranspiration estimation results are analyzed and evaluated. The results observed within the oasis and the banks of the river suggest that more evapotranspiration occurs in the inland river basin in the arid region from May to September. Evapotranspiration values for the oasis, where the land surface types and vegetations are highly variable, are relatively small and heterogeneous. In the Gobi desert and other deserts with little vegetation, evapotranspiration remains at its lowest level during this period. These results reinforce the conclusion that rational utilization of water resources in the oasis is essential to manage the water resources in the inland river basin. In the remote sensing-based evapotranspiration model, the accuracy of the parameter estimate directly affects the accuracy of the evapotranspiration results; more accurate parameter values yield more precise values for evapotranspiration. However, when using the evaporative fraction to estimate regional evapotranspiration, better calculation results can be achieved only if evaporative fraction is constant in the daytime.
A clear understanding of a model is important for its appropriate use. In this article, eleven watershed scale hydrologic and nonpoint-source pollution models are reviewed: AGNPS, AnnAGNPS, ANSWERS, ANSWERS-Continuous, CASC2D, DWSM, HSPF, KINEROS, MIKE SHE, PRMS, and SWAT. AnnAGNPS, ANSWERS-Continuous, HSPF, and SWAT are continuous simulation models useful for analyzing long-term effects of hydrological changes and watershed management practices, especially agricultural practices. AGNPS, ANSWERS, DWSM, and KINEROS are single rainfall event models useful for analyzing severe actual or design single-event storms and evaluating watershed management practices, especially structural practices. CASC2D, MIKE SHE, and PRMS have both long-term and single-event simulation capabilities. Mathematical bases, the most important and critical elements of these mathematical models, were identified and compiled. In this article, a comprehensive summary of the compilation is presented in tabular form. The flow-governing equations and their solution methods used in each of the eleven models are discussed. The compilation of the mathematical bases of these models would be useful to determine the problems, situations, or conditions for which the models are most suitable, the accuracies and uncertainties expected, their full potential uses and limitations, and directions for their enhancements or new developments. AGNPS, AnnAGNPS, DWSM, HSPF, MIKE SHE, and SWAT were found to have all the three major components (hydrology, sediment, and chemical) applicable to watershed-scale catchments. SWAT is a promising model for continuous simulations in predominantly agricultural watersheds, and HSPF is promising for mixed agricultural and urban watersheds. Among the single-event models, DWSM provides a balance between the simple but approximate and the computationally intensive models and, therefore, is a promising storm event model for agricultural watersheds.
Changes in development and use of water resources over the last 30 years have led to significant environmental and hydrological degradation of the River Heihe basin in the People's Republic of China. Water discharge of the lower reaches has been seriously compromised and more than 30 tributaries and terminal lakes have dried up. The water output of springs has dropped significantly. Also water quality problems have been observed, in both surface waters and groundwater. Hydrological changes have resulted in a marked degradation of aquatic habitats, and have caused substantial, and expanding, land salinization and desertification. Solving these problems, which have been largely caused by human activities, requires massive and long-lasting concerted efforts.
We investigate the effects of land-use change in the semi-arid Lerma basin (Ebro valley, Spain), which underwent a transition from rainfed towards irrigation agriculture. For four consecutive years, this transition of formerly uncultivated land to irrigated farmland was intensively monitored. We use the calibrated and validated, physics-based, 3-D fully-coupled model HydroGeoSphere to study the hydrological effects of the change for this unique site, where spatio-temporal data on cropping patterns, irrigation and fertilizer amounts, and the associated catchment response are available with comparatively high resolution. Validation results show that the physics-based model can simulate and predict the impact of the land-use transformation and irrigation on surface and subsurface flow dynamics with high accuracy. Sensitivity and correlation analyses about the calibrated model parameter vector indicate that the set of van Genuchten parameter values and hydraulic conductivities is identifiable and locally unique for the parameter zonation that was defined using information on lithological units and texture data. In order to indicate changes in the runoff generation process and catchment functioning, we analyze the evolution of the total stream length and the average infiltration capacity provided by the model. The results show that irrigation agriculture has raised the base level of the water table of the Lerma aquifer causing new portions of the drainage network to become perennial. Furthermore, we introduce an approximate infiltration capacity, analyze its evolution and study its effect on Hortonian overland flow. Due to the physics-based nature of the model we can obtain values for exfiltrating fluxes directly from the model and show that both, the approximate infiltration capacity curve and the contribution of exfiltration to stream flow are consistent in indicating a shift from Hortonian towards Dunne flow runoff generating processes triggered by the land-use change.Highlights► Physics-based model keeps high prediction accuracy despite ongoing land-use change. ► Van Genuchten values identifiable through parameter range restriction. ► Total stream length analysis reveals upward shift of topographic spring level. ► Irrigation increases Dunne runoff component intensifying system coupling.
Irrigation is the most important water use sector accounting for about 70% of the global freshwater withdrawals and 90% of consumptive water uses. While the extent of irrigation and related water uses are reported in statistical databases or estimated by model simulations, information on the source of irrigation water is scarce and very scattered. Here we present a new global inventory on the extent of areas irrigated with groundwater, surface water or non-conventional sources, and we determine the related consumptive water uses. The inventory provides data for 15 038 national and sub-national administrative units. Irrigated area was provided by census-based statistics from international and national organizations. A global model was then applied to simulate consumptive water uses for irrigation by water source. Globally, area equipped for irrigation is currently about 301 million ha of which 38% are equipped for irrigation with groundwater. Total consumptive groundwater use for irrigation is estimated as 545 km<sup>3</sup> yr<sup>−1</sup>, or 43% of the total consumptive irrigation water use of 1 277 km<sup>3</sup> yr<sup>−1</sup>. The countries with the largest extent of areas equipped for irrigation with groundwater, in absolute terms, are India (39 million ha), China (19 million ha) and the United States of America (17 million ha). Groundwater use in irrigation is increasing both in absolute terms and in percentage of total irrigation, leading in places to concentrations of users exploiting groundwater storage at rates above groundwater recharge. Despite the uncertainties associated with statistical data available to track patterns and growth of groundwater use for irrigation, the inventory presented here is a major step towards a more informed assessment of agricultural water use and its consequences for the global water cycle.
The history of the kinematic wave theory and its applications in water resources are traced. It is shown that the theory has found its niche in water resources and its applications are so widespread that they may well constitute what may be termed ‘kinematic wave hydrology’. Few theories have been applied in hydrology and water resources as extensively as the kinematic wave theory. This theory, however, is not without limitations and when it is applied they must be so recognized. Copyright © 2001 John Wiley & Sons, Ltd.
Surface water and groundwater in the Heihe river basin of China are interconnected and the pattern of water resources exploitation has a direct effect on the interaction of groundwater and surface water, especially on a downstream oasis. A three-dimensional groundwater flow simulation model with eight model layers was established to simulate the regional groundwater flow in the multilayered aquifer system and the interaction among the rivers, springs, and groundwater. The model was calibrated not only with historical water levels but also with the investigated baseflow and spring flux. The simulation results of the numerical model match reasonably well with the observed groundwater levels, baseflow to rivers, and spring flux. The numerical simulation also demonstrates that the hydraulic connection between the river and the aquifers has transferred from the coupling to decoupling at some reaches. It is suggested that there is a vital need to reduce groundwater withdrawal and to rationalize the use of both groundwater and surface water in order to maintain sustainable development in the study area. Copyright © 2007 John Wiley & Sons, Ltd.
A conceptual, continuous time model called SWAT (Soil and Water Assessment Tool) was developed to assist water resource managers in assessing the impact of management on water supplies and nonpoint source pollution in watersheds and large river basins. The model is currently being utilized in several large area projects by EPA, NOAA, NRCS and others to estimate the off-site impacts of climate and management on water use, non-point source loadings, and pesticide contamination. Model development, operation, limitations, and assumptions are discussed and components of the model are described. In Part II, a GIS input/output interface is presented along with model validation on three basins within the Upper Trinity basin in Texas.
This paper analyzed the dynamic change of the groundwater level by 6years’ monitoring in field monitoring and the change
of vegetation by the field survey and satellite remote sensing after watering in the lower reaches of Heihe River. The findings
indicated: (1) the groundwater level elevation and the plant growth are closely related to the volume and the duration of
watering. In general, groundwater level elevates dramatically and plants are growing much more vigorously after watering;
(2) Watering incidence on groundwater keeps extending with the watering times increasing; (3) Plants grew rapidly in 100–400m
away from the water channel after watering. Watering incidence on vegetation reached 1,000m; (4) In terms of the function
and structure of ecosystem after watering in the lower reaches of Heihe River, the ecological water conveyance does not still
reach the goal of ecological restoration at a large spatial scale at present. In addition, in order to solve fundamentally
the problem of ecological environment worsens in the lower reaches of Heihe River, some suggestions and countermeasures are
put forward.
The Zhangye Region of Gansu Province is an important agricultural base in arid northwestern China. During the twentieth century, especially in the last five decades, the region has experienced sandy desertification. To document the status and causes of this deterioration, satellite images, meteorological and socioeconomic data to assess landscape change from 1993 to 2002 were interpreted and analyzed. The results show that during the intervening 9-year period the area of sandy lands has increased by 642.2km2, which consist of aeolian sand dune (357.1km2) and potential sandy land (216.3km2). Although the development and reversion of sandy desertification co-exist, the sandy desertification in this area seems serious and is attributable to the irrational use of water and land.
An analysis, over historical times, of the influence of natural factors such as climate, geological activity, existing landforms,
and the activity of aeolian sands on the desertification of oases and other lands in the Heihe River basin of northwestern
China revealed that desertification occurred more or less quickly according to whether the prevailing climate was cold or
warm, respectively. In the 1990s, the area of desertified lands in the lower reaches of the Heihe River (Ejin region) was
29.1% greater than in the mid 1980s. However, the rate of desertification in the middle reaches of the Heihe River basin was
relatively slower, only 9.4% from 1949 to 1990 (or 0.27% per year). Since 1990, the rate of desertification has been stable.
By 2000, the total area of land desertification in the mid to lower reaches of the Heihe River basin was 13,508.4km2, or 11.8% of the region monitored. Of the total land desertification area, the regions of Linze, Gaotai, Sunan, Jiuquan,
Jia Yuguan, and Jinta accounted for 1.70, 1.71, 1.43, 0.85, 0.28, and 9.39%, respectively, whereas the Ejin region’s 11,434.64km2 accounted for 84.65%, indicating that land desertification in the lower Heihe River basin was particularly severe. The causes
responsible for the occurrence and development of land desertification in the Heihe River basin were analyzed.
KeywordsHeihe River basin-Land desertification in historical period-Modern land desertification-Origin analysis
The recharge and origin of groundwater and its residence time were studied using environmental isotopic measurements in samples from the Heihe River Basin, China. δ18O and δD values of both river water and groundwater were within the same ranges as those found in the alluvial fan zone, and lay slightly above the local meteoric water line (δD=6.87δ18O+3.54). This finding indicated that mountain rivers substantially and rapidly contribute to the water resources in the southern and northern sub-basins. δ18O and δD values of groundwater in the unconfined aquifers of these sub-basins were close to each other. There was evidence of enrichment of heavy isotopes in groundwater due to evaporation. The most pronounced increase in the δ18O value occurred in agricultural areas, reflecting the admixture of irrigation return flow. Tritium results in groundwater samples from the unconfined aquifers gave evidence for ongoing recharge, with mean residence times of: less than 36 years in the alluvial fan zone; about 12-16 years in agricultural areas; and about 26 years in the Ejina oasis. In contrast, groundwater in the confined aquifers had 14C ages between 0 and 10 ka BP.
The Zhangye basin is in the middle reaches of the Heihe River, northwestern China. Heavy abstraction of groundwater since
the 1970s in the area is for agricultural, industrial and drinking water supplies and has led to a substantial decline in
the potentiometric surface. A three-dimensional regional numerical groundwater flow model, calibrated under transient conditions,
has been developed and used to predict the drawdown for the period from 2000 to 2030 under two different groundwater management
scenarios.
Much attention has been paid to uncertainty issues in hydrological modelling due to their great effects on prediction and further on decision-making. The uncertainty of model parameters is one of the major uncertainty sources in hydrological modelling. The aim of this study is to quantify the parameter uncertainty in Soil and Water Assessment Tool (SWAT) model using bootstrap method with application to Yingluoxia watershed located in the upper reaches of Heihe River basin. Bootstrap method is a nonparametric technique for simulating the parameter distribution. Nine sensitive aggregate parameters are investigated. The results from bootstrap method show that six of the nine marginal distributions are not normally distributed and each parameter has its own uncertainty range. Further investigation about the effects of parameter uncertainty on simulation results shows that although the parameter uncertainty is one of the important sources of uncertainties, its contribution to simulation uncertainty is relatively small. Only 12–13% of the observed runoff data fall inside the 95% simulation confidence intervals in the calibration and validation periods. For a better understanding of the applicability of bootstrap method, the commonly used Bayesian approach is also investigated for comparison. Results show that the approximate results are obtained from both methods, not only in the percentage of observations falling inside the 95% confidence interval of simulations, but also in the uncertainty range of parameters, although the range obtained from Bayesian method is slightly narrower than that from bootstrap method, possibly due to the correlation structure amongst parameters in the MCMC (Markov Chain Monte Carlo) simulation employed in Bayesian method. The computational efficiencies of both methods presented are comparable as well.
In this second of two papers, analytical step-response functions, developed in the companion paper for several cases of transient hydraulic interaction between a fully penetrating stream and a confined, leaky, or water-table aquifer, are used in the convolution integral to calculate aquifer heads, streambank seepage rates, and bank storage that occur in response to stream-stage fluctuations and basinwide recharge or evapotranspiration. Two computer programs developed on the basis of these step-response functions and the convolution integral are applied to the analysis of hydraulic interaction of two alluvial stream–aquifer systems in the northeastern and central United States. These applications demonstrate the utility of the analytical functions and computer programs for estimating aquifer and streambank hydraulic properties, recharge rates, streambank seepage rates, and bank storage. Analysis of the water-table aquifer adjacent to the Blackstone River in Massachusetts suggests that the very shallow depth of water table and associated thin unsaturated zone at the site cause the aquifer to behave like a confined aquifer (negligible specific yield). This finding is consistent with previous studies that have shown that the effective specific yield of an unconfined aquifer approaches zero when the capillary fringe, where sediment pores are saturated by tension, extends to land surface. Under this condition, the aquifer's response is determined by elastic storage only. Estimates of horizontal and vertical hydraulic conductivity, specific yield, specific storage, and recharge for a water-table aquifer adjacent to the Cedar River in eastern Iowa, determined by the use of analytical methods, are in close agreement with those estimated by use of a more complex, multilayer numerical model of the aquifer. Streambank leakance of the semipervious streambank materials also was estimated for the site. The streambank-leakance parameter may be considered to be a general (or lumped) parameter that accounts not only for the resistance of flow at the river–aquifer boundary, but also for the effects of partial penetration of the river and other near-stream flow phenomena not included in the theoretical development of the step-response functions.
The planning and management of water resources in the Pioneer Valley, north-eastern Australia requires a tool for assessing the impact of groundwater and stream abstractions on water supply reliabilities and environmental flows in Sandy Creek (the main surface water system studied). Consequently, a fully coupled stream–aquifer model has been constructed using the code MODHMS, calibrated to near-stream observations of watertable behaviour and multiple components of gauged stream flow. This model has been tested using other methods of estimation, including stream depletion analysis and radon isotope tracer sampling. The coarseness of spatial discretisation, which is required for practical reasons of computational efficiency, limits the model’s capacity to simulate small-scale processes (e.g., near-stream groundwater pumping, bank storage effects), and alternative approaches are required to complement the model’s range of applicability.Model predictions of groundwater influx to Sandy Creek are compared with baseflow estimates from three different hydrograph separation techniques, which were found to be unable to reflect the dynamics of Sandy Creek stream–aquifer interactions. The model was also used to infer changes in the water balance of the system caused by historical land use change. This led to constraints on the recharge distribution which can be implemented to improve model calibration performance.
The Wakool Irrigation District consists of 74,000 ha of agricultural land, a large part of which is affected by a rising watertable. Irrigation in the district started in 1936 when the watertable depth was about 9 m. Over the past 30 years, the watertable has risen as a consequence of irrigation, wet winters and inadequate drainage. In addition, the Wakool Irrigation District is underlain by the Calivil and Renmark aquifers of the Murray Basin. Rising groundwater pressures in these deeper aquifers are also contributing to the rising shallow watertable. Since 1981, a sub-surface drainage scheme with 48 bores pumping shallow saline groundwater into a 2000 ha evaporation basin has been developed in two stages to control the watertable in the Wakool Irrigation District. This paper describes the development and application of an integrated hydrogeological model for the Wakool Irrigation District, where management of rising watertable levels and land salinisation is a continuing problem. The model development is considered to be an important part in the establishment of sustainable water management policies for the Wakool Irrigation District. The Wakool model was developed by using the MIKE SHE integrated catchment-modelling package. The developed model enables analysis of the complex hydrogeological regime in the region, and prediction of the environmental impacts of various management options. It is able to describe temporal and spatial variations in the exchange of water between the land surface, drainage and supply systems, and the aquifers within the area. Management options proposed in the Wakool Land and Water Management Plan have been analysed for the period between 1975 and 2020. Various scenarios such as the implementation of on-farm recycling ponds in conjunction with laser levelling, deep-rooted perennials, tree planting, installation of deep groundwater pumps and the effect of shallow groundwater pumping, were investigated. The results from these simulations indicate that the best option is the implementation of shallow pumping.
A physically-based, spatially-distributed model is presented for simulation of surface/subsurface flow and the interactions between these domains. The model is designed for practical application to a wide variety of hydrologic evaluations, at various scales of simulation. The system is represented by the three-dimensional saturated–unsaturated flow equation for the subsurface, coupled with the diffusion wave equation for areal overland flow, both of which are coupled with the diffusion wave equation for flow through a network of streams and channels, including hydraulic structures. Ground surface unevenness at the grid scale is incorporated via the concept of detention storage, and thick vegetation or urban features are included via an obstruction storage exclusion term. Evapotranspiration from the surface and subsurface are modeled using land cover and climatic factors to define the complete water budget using a physically-based formulation. The system of equations is discretized using a fully implicit procedure, with the Newton–Raphson method to handle non-linearities efficiently. Robustness, stability and accuracy of solution are obtained for a wide variety of cases including dry systems and large surface/subsurface interaction fluxes. Adaptive time-stepping schemes and under-relaxation formulas further alleviate the computational burden. Verification and application examples demonstrate the need for a rigorous, fully-coupled solution to the set of equations, for complete hydrologic-cycle analysis.
The objective of this article is to develop and implement a comprehensive computer model that is capable of simulating the surface-water, ground-water, and stream-aquifer interactions on a continuous basis for the Rattlesnake Creek basin in south-central Kansas. The model is to be used as a tool for evaluating long-term water-management strategies. The agriculturally-based watershed model SWAT and the ground-water model MODFLOW with stream-aquifer interaction routines, suitably modified, were linked into a comprehensive basin model known as SWATMOD. The hydrologic response unit concept was implemented to overcome the quasi-lumped nature of SWAT and represent the heterogeneity within each subbasin of the basin model. A graphical user-interface and a decision support system were also developed to evaluate scenarios involving manipulation of water rights and agricultural land uses on stream-aquifer system response. An extensive sensitivity analysis on model parameters was conducted, and model limitations and parameter uncertainties were emphasized. A combination of trial-and-error and inverse modeling techniques were employed to calibrate the model against multiple calibration targets of measured ground-water levels, streamflows, and reported irrigation amounts. The split-sample technique was employed for corroborating the calibrated model. The model was run for a 40 y historical simulation period, and a 40 y prediction period. A number of hypothetical management scenarios involving reductions and variations in withdrawal rates and patterns were simulated. The SWATMOD model was developed as a hydrologically rational low-flow model for analyzing, in a user-friendly manner, the conditions in the basin when there is a shortage of water.
The solutions of the Saint-Vénant equations are compared with those of the kinematic, diffusion and gravity wave approximations, for a range of constant Froudé and kinematic wave numbers, with two different lower boundary conditions: (1) critical flow; and (2) zero depth gradient. For each lower boundary condition, zones are defined in the F0,k-field in which either kinematic, diffusion or gravity wave solutions may be used to approximate the full Saint-Vénant solutions.
Spatial interpolation of climatic data is frequently required to provide input for plant growth models. As no single method is optimal for all regions, it is important to compare the results obtained using alternative methods applied to each data set. For estimating 30-year averages (Normals) of monthly temperature and precipitation at specific sites in western Canada, we examined four forms of kriging and three simple alternatives. One of the alternatives was a novel technique, termed `gradient-plus-inverse distance squared' (GIDS), which combines multiple linear regression and distance-weighting. Based on the mean absolute errors from cross-validation tests, the methods were ranked GIDS > detrended kriging > nearest neighbour >co-kriging > inverse distance squared > universal kriging > ordinary kriging for interpolating monthly temperature, and GIDS > co-kriging>inverse distance squared > nearest neighbour > ordinary kriging > detrended kriging > universal kriging for interpolating monthly precipitation. GIDS gave the lowest errors, which averaged 0.5°C for monthly temperature and 3.6 mm, or 11%, for monthly precipitation. These errors were comparable with those from optimal methods in other studies. GIDS errors were also more consistent for a wide range of data variability than the other methods. The performance of kriging may have been constrained by the limited number of stations (32) in the study region, but if so, this is an unavoidable limitation in regions with sparse coverage of climate stations. Compared with kriging, GIDS was simple to apply and avoided the subjectivity involved in defining variogram models and neighbourhoods. We conclude that GIDS is a simple, robust and accurate interpolation method for use in our region, and that it should be applicable elsewhere, subject to careful comparison with other methods.
The principles governing the application of the conceptual model
technique to river flow forecasting are discussed. The necessity for a
systematic approach to the development and testing of the model is
explained and some preliminary ideas suggested.