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Quantifying the combined effects of land use and climate changes on stream flow and nutrient loads: A modelling approach in the Odense Fjord catchment (Denmark)
Abstract
Water pollution and water scarcity are among the main environmental challenges faced by the European Union, and multiple stressors compromise the integrity of water resources and ecosystems. Particularly in lowland areas of northern Europe, high population density, flood protection and, especially, intensive agriculture, are important drivers of water quality degradation. In addition, future climate and land use changes may interact, with uncertain consequences for water resources. Modelling approaches have become essential to address water issues and to evaluate ecosystem management. In this work, three multi-stressor future storylines combining climatic and socio-economic changes, defined at European level, have been downscaled for the Odense Fjord catchment (Denmark), giving three scenarios: High-Tech agriculture (HT), Agriculture for Nature (AN) and Market-Driven agriculture (MD). The impacts of these scenarios on water discharge and inorganic and organic nutrient loads to the streams have been simulated using the Soil and Water Assessment Tool (SWAT). The results revealed that the scenario-specific climate inputs were most important when simulating hydrology, increasing river discharge in the HT and MD scenarios (which followed the high emission 8.5 representative concentration pathway, RCP), while remaining stable in the AN scenario (RCP 4.5). Moreover, discharge was the main driver of changes in organic nutrients and inorganic phosphorus loads that consequently increased in a high emission scenario. Nevertheless, both land use (via inputs of fertilizer) and climate changes affected the nitrate transport. Different levels of fertilization yielded a decrease in the nitrate load in AN and an increase in MD. In HT, however, nitrate losses remained stable because the fertilization decrease was counteracted by a flow increase. Thus, our results suggest that N loads will ultimately depend on future land use and management in an interaction with climate changes, and this knowledge is of utmost importance for the achievement of European environmental policy goals.
... Moreover, in Northern regions nutrient (such as nitrogen) losses from soils are expected to increase [22,23] caused by increase in mineralization rates and loss of snow cover in cold periods [24]. Meaning that substantially changing costs for protecting water ecosystems and resources, which are vital for the survival and development of societies. ...
... However, none of them were connected to the implementation of the WFD or Baltic Sea Action Plan (BSAP) to implement the Helsinki convention. Even though there are plenty of studies in surrounding countries focusing more on environmental management related questions [24,35,37,[56][57][58], very few attempts have been found integrating multiple water management questions at required scale and providing answers, which might be directly relevant to management institutions. It is especially relevant today, because despite significant efforts, diffuse water pollution in Lithuania and other countries remains either stable or is still worsening [13,14,[59][60][61]. ...
... The review of studies provided by the HELCOM report [69] presents multiple studies covering the Baltic Sea region. Also climate impact assessments are presented in studies focusing on fjords [24], lagoons, large river basins [55,70] and smaller river basins [36,71,72]. ...
This study aims to evaluate how climate change affects agricultural diffuse water pollution, the effectiveness of pollution abatement measures, and water management programs in Lithuania. The work assesses changes in water and nutrient balances across the country, examines shifts in the effectiveness of pollution control measures, and estimates the necessary scale and design of water management programs to achieve water protection goals given the warming climate. Conducted in collaboration with the Lithuanian Environmental Protection Agency, the research addresses practical water management issues and aligns with national environmental targets. The study integrates climate impact assessment, hydrological modeling, modeling the best management practices, optimization with genetic algorithms, and the evaluation of achievement of water environmental goals. Additionally, a new tool was developed and provided for SWAT+ model setup verification to enhance confidence in modeling results, which is crucial for informing water management decisions. The findings, disseminated across four publications, offer comprehensive insights into the intersection between climate change, water and environmental management related aspects in Lithuania.
... Numerous authors have investigated the impact of climate change on hydrology, nutrient loads and ecosystem impacts at different scales (Jeppesen et al., 2009, Jeppesen et al., 2011Alcamo and Olesen, 2012;Arias et al., 2021). Land use changes both alone and combined with climate changes have also been explored in many studies in the Nordic-Baltic region, including the River Odense catchment that was appointed as one of the Danish pilot river basins for implementation of the EU WFD (Environment Centre Odense, 2007;Karlsson et al., 2016;Molina-Navarro et al., 2018;Trolle et al., 2019). Karlsson et al. (2016) investigated the combined effects of climate models, hydrological model structures and land use change scenarios on the hydrological impacts of climate change. ...
... They found little impact of land use change scenarios for the mean hydrological catchment responses and concluded that choice of climate model was the dominant factor regarding the hydrological response in the catchment. Molina-Navarro et al. (2018) quantified the combined effects of land use and climate change simulations on the stream flow and nutrient loads in the River Odense catchment. They found that nitrogen (N) loads depend on the future land use and management. ...
... To compare the simulated and observed streamflow, the Nash-Sutcliffe Efficiency (NSE) was used as the objective function. Other authors also used NSE as an objective function in similar catchments (Molina-Navarro et al., 2018). For streamflow, 25 parameters were calibrated at basin level. ...
A societal transformation towards bio-economy will have extensive implications for land use in Nordic countries. These expected changes in land use combined with a changing climate, will have unknown consequences for water quality and quantity. To address this issue, we used the Nordic Bio-economic Pathways (NBPs), which describe five possible future scenarios (NBP1-5) for the Nordic bio-economy in 2050. The NBPs were quantified by experts using local knowledge and translated into modelling scenarios. The SWAT model was applied to simulate the effect of NBP scenarios for changes in farming intensity (varying chemical fertilizer and manure application rates), land cover change (agriculture vs forest) and nutrient loss mitigation (buffer strips and wetlands) in the River Odense catchment. Subsequently, the NBPs were combined with medium (RCP4.5) and strong (RCP8.5) climate change scenarios for the period 2041–2070 utilising the median of an ensemble of 20 and 57 climate models, respectively. Our study clearly showed that only one of the pathways, namely NBP1 (sustainability first), would enable catchment managers to fulfil the Water Framework Directive reduction target set for the total nitrogen loads in the River Odense catchment by reducing total nitrogen loads by 66%. One of the pathways (NBP5; growth first) caused an increase in the average annual total nitrogen loads by 12%, while the NBP3 scenario (self-sufficiency) reduced the total nitrogen loads with 18% compared to 2% in the case of NBP2 (business as usual) and 29 % for NBP4 (cities first). Surprisingly, climate change had only limited added impacts on the total nitrogen loads due to increased nitrogen uptake of crops. Our study provides policy makers with information on the influence of the different choices and directions taken towards transforming societies into bio-economies in the future.
... However, most studies are focused on a particular river or water body (as lake, lagoon or fjord) basin. For instance, a study of Molina-Navarro et al. (2018) is focused on Danish fjord, while a study of Č erkasova et al. (2016) -on the Curonian lagoon or the Nemunas river basin focused study by Kriau či ūnien ė et al. (2008) . Only a few of them take the whole country as a study object. ...
... It has also been broadly used for the hydro-climatic questions ( Tan et al., 2020 ). SWAT has been widely utilized for dealing with questions important in the Baltic Sea basin, which relate to the implementation of River Basin Management Plans required by EU Directive 20 0 0/60/EC (the so-called Water Framework Directive, thereafter -WFD) and Country Allocated Reduction Targets required by BSAP ( Andersen et al., 2016;Hesse et al., 2014;Huttunen et al., 2015;Molina-Navarro et al., 2018;Piniewski et al., 2021;Thodsen et al., 2017 ). It has been successfully applied for hydro-climatic questions in Lithuania as well ( Č erkasova, 2019; Č erkasova et al., 2019 ). ...
... Multiple European scale studies ( Lobanova et al., 2018;Marx et al., 2017;Schneider et al., 2013 ) confirm that the Northern region is expected to face a stream flow increase, the scale of which will be correlated with climate change intensity. The same conclusion is made in studies for the Scandinavian countries in the Baltic Sea catchment ( Molina-Navarro et al., 2018;The BACC II Author Team, 2015 ). Study by Tamm et al. (2018) on Estonian rivers combining highresolution EURO-CORDEX project RCM data with SWAT modeling also obtained results, which predict an increase in annual runoff. ...
The study evaluated climate change impact on water flows and nutrient loads to surface water bodies in Lithuania by applying the SWAT model. Seven RCM and GCM combinations were selected and RCP4.5 and RCP8.5 climate change representative concentration pathways were selected for the study. The study concluded that an annual and winter increase in most river water flows are expected. The change will be driven by rising precipitation, mainly in the regions where it is already high. Less snow would result in less surface runoff, substituted by increased lateral and groundwater flows because of more water percolating through the soils. As a result, water flows could be expected to increase by 9.7% for RCP4.5 and by 35.4% for the RCP8.5 climate scenario by the end-century. Whereas sediment transport and phosphorus loads would tend to decline a little bit (median results are -11.4% and -5.6% respectively for the RCP4.5 scenario, -13.3% and -7.4% for the RCP8.5 by the end of century). Conversely, temperature driven nutrient mineralization and increased leaching are expected to cause a significant increase in nitrogen loads (by 23.1% for the RCP4.5 scenario and by 64.4% for the RCP8.5 by the end of century). Overall, it could be concluded that climate change related hydrometeorological and water quality changes were found to be the most profound for the end-century RCP8.5 climate change scenario.
... Kundzewicz et al. (2018) report that while approximately 60% of major rivers exhibit trends consistent with projections, others show significant deviations, particularly concerning seasonal variability in tropical regions like the Amazon basin. Furthermore, Molina-Navarro et al. (2018) attribute localized inconsistencies to a combination of climatedriven changes and human activities, such as land-use changes and over-extraction of water resources. For example, Rockström et al. (2009) identify unsustainable practices as key contributors to water stress, often independent of climatic factors. ...
... Kundzewicz et al. (2018) report that while around 60% of major rivers exhibit trends consistent with projections, others reveal overestimated or underestimated seasonal variability, particularly in tropical regions like the Amazon basin. Additionally, Molina-Navarro et al. (2018) found that localized precipitation trends often deviate from earlier forecasts, suggesting that observed changes might stem from a mix of climate impacts and human-driven factors, including land-use changes and over-extraction of water resources, (Falkenmark and Lannerstad 2005;Rockström et al., 2009;Chahed et al., 2015). ...
This article investigates the methodological advancements and challenges in climate modeling, focusing on hydrological projections and their application in adaptive water governance frameworks. By exploring the evolution of the Coupled Model Intercomparison Project (CMIP), the paper highlights key advancements, including improved representations of biogeochemical cycles, regional variability, and advanced parameterizations. Specific emphasis is placed on microphysical processes that are critical to precipitation formation but remain major sources of uncertainty in hydrological projections. The article emphasizes the need to address these uncertainties through refined modelling methodologies and the incorporation of robust observational data. Experimental studies and advanced tools, including numerical simulations and machine learning emulators, are essential for linking fine-scale dynamics with global models and enhancing predictions of hydrological feedbacks. The synthesis highlights practical applications, emphasizing how refined models and a precise understanding of uncertainties support adaptive and sustainable water management, particularly in regions under acute stress. This interdisciplinary approach bridges technical precision and governance, providing actionable pathways for addressing global water challenges.
... Moreover, many authors (Barclay and Walter 2015;Øygarden et al.; expect increased nutrient losses (primarily nitrogen) from soils. In the Nordic-Baltic region, higher nitrogen mineralisation due to rising temperatures and precipitation in cold periods are expected to increase leaching of nitrates (Molina-Navarro et al. 2018). Higher nutrient loads together with the likely prolongation of the growing period could further exacerbate the already severe eutrophication problems in places such as the Baltic Sea (HELCOM 2018a). ...
... Multiple studies have employed it for questions related to the impact of CC on agricultural pollution (Bosch et al. 2018;Brouziyne et al. 2018;Jeon et al., 2018;Qiu et al. 2020;Teshager et al. 2017;Wagena and Easton 2018;Woznicki and Nejadhashemi 2014). SWAT has been extensively applied for investigating water policy and management questions (Molina-Navarro et al., 2018;Piniewski et al. 2021; Thodsen et al. 2017). Furthermore, a number of studies integrated the model with Genetic Algorithms (GA) for delivering optimized solutions for BMPs selection and spatial distribution for reaching water protection goals (Geng et al. 2019;Kaini et al. 2012;Naseri et al., 2021). ...
This study aimed at evaluating the scale and costs of an environmentally and economically optimal set of Best Management Practices (BMPs) for agricultural pollution abatement in Lithuania in order to reach water protection goals in both inland and marine waters by distributing BMPs optimally in space, while taking climate change impacts into consideration. The assessment of BMPs impact involved the use of the SWAT model by applying two climate change representative concentration pathways (RCP4.5 and RCP8.5) and two time horizons (mid-century and end-century), as well as five BMPs (arable land conversion to grasslands, reduced fertilization, no-till farming, catch-crops, and stubble fields throughout winter). The optimization of the set of BMPs employed a genetic algorithm. The results suggest that the need for BMPs application will increase from 52% of agricultural areas in the historical period up to 65% by the end of century in the RCP8.5 scenario. This means less arable land could actually be used for crop production in the future if water protection targets are met. The high costs for reaching water targets would rise even more, i.e. by 173% for RCP4.5, and by 220% for the RCP8.5 scenario, reaching approximately 200 million euros/year. In such a context, the BMP optimization approach is essential for significant reduction of the costs. Winter cover crops and reduced fertilization show the best effectiveness and cost balance, and will therefore be essential in pursuing water protection targets.
... Studies show (Bosch et al., 2018;Qiu et al., 2020;Renkenberger et al., 2017) that CC will likely increase the cost of meeting water quality goals in water bodies affected by agriculture. For instance, in the Nordic-Baltic region, higher temperatures may increase nitrogen mineralisation, and increased precipitation in the cold period may create more favourable conditions for nitrate (NO3-N) leaching (Molina-Navarro et al., 2018). Next to increasing nutrient loads, CC is likely to change the spatial distribution patterns of agri NPS, and cause substantial changes in areas identified as Critical Source Areas (Renkenberger et al., 2017). ...
... It has been widely applied in hydro-climatic studies (Tan et al., 2020). The SWAT model has also been used extensively for the assessment of water policy and management options (Andersen et al., 2016;Hesse et al., 2014;Huttunen et al., 2015;Molina-Navarro et al., 2018;Piniewski et al., 2021;Thodsen et al., 2017). The advantages of the SWAT model include its past successful application in many studies integrating CC and agri NPS pollution reduction issues (Bosch et al., 2018;Brouziyne et al., 2018;Jeon et al., 2018;Qiu et al., 2020;Renkenberger et al., 2017;Teshager et al., 2017;Wagena and Easton, 2018;Woznicki and Nejadhashemi, 2014;Xu et al., 2019). ...
This study aimed at the evaluation of the change in the effectiveness of Best Management Practices (BMPs) for agricultural pollution control in terms of reduction of nutrient loads to surface water bodies in Lithuania in the context of climate change (CC). The SWAT model was used by applying two CC representative concentration pathways (RCP4.5 and RCP8.5), three time horizons (historical – 2000–2019, mid-century – 2040–2059, and end-century – 2080–2099), and five BMPs (arable land conversion to grasslands, reduced fertilization, no-till farming, catch-crops, and stubble fields throughout winter). The most effective (with the greatest nutrient reduction) BMPs include grasslands, stubble fields, and winter cover crops. No-plough farming and reduced fertilization BMPs appear to be the least effective ones. CC would increase the potential of reduced fertilization and conversion to grasslands BMPs up to 179% and 17%, respectively for total nitrogen (TN) reduction. Regarding total phosphorus (TP), the reduction potential would increase 226% for fertilization reduction, and remain approximate for grasslands (at median −4%). Due to winter reduction of loads, no-plough stubble fields, and winter cover crops would decrease by as much as − 50%, − 12% and − 26%, respectively for TN, and − 30%, − 11%, and − 17%, respectively for TP, compared to the historical period. The greatest change would be recorded for the most extreme CC scenario (RCP8.5) and the longest time horizon (end-century). The effectiveness of BMPs (except for no-plough) for TN load reduction would increase more, and on average would become greater in agriculture dominated areas (of central-northern Lithuania) than elsewhere, although the maximum reduction values would occur in western (and in some cases eastern) Lithuania (except for reduced fertilization). This suggests the importance of the application of the measures in both areas. BMPs (except for grasslands) are expected to have relatively little effect on the overall crop yield.
... In nutrient cycles around the world, lack of understanding in seasonal relationships between hydrology, climatology, and biogeochemistry is a rich area for researchespecially at the regional scale (Lohse et al. 2009). In Denmark, scientists have found projected increases in precipitation and changes in air temperature (T) increase TN loads and export (Andersen et al. 2006), increase P loading from land to streams, release P from lake sediments (Jeppesen et al. 2000a), and increase discharge of organic nutrients and dissolved inorganic phosphorus (DIP), anddepending on future land usesdecrease nitrate (NO À 3 ) transport (Molina-Navarro et al. 2018). Dissolved inorganic nitrogen (DIN) concentrations and loads are known to be influenced by agricultural land uses and fertilizers, and seasonal N export has been found to correlate with climate, anthropogenic N inputs, and discharge (Q) (Boyer et al. 2002;Dumont et al. 2005;Sobota et al. 2009). ...
... In the context of climate change, precipitation is known to dominate interannual variability of TN in the U.S. (Sinha and Michalak 2016). Similarly, researchers in Denmark found that nutrient loads relate to precipitation and air temperature (Jeppesen et al. 2000a;Andersen et al. 2006;Molina-Navarro et al. 2018). As expected, precipitation and high Q were found to be significant, positive predictors for nutrient loads across most watersheds (regression coefficients were 0.41 and 0.15 for Precip and DIN loads, and 0.017 for Precip and DIP loads; Tables 5 and 8, respectively. ...
Understanding the temporal dynamics and drivers of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) provides a critical link to better management of nutrient‐related impacts such as eutrophication and harmful algal blooms (HABs). DIN and DIP are a primary control on persistent eutrophication and HABs in the Pacific Northwest (PNW). An understudied phenomenon, this paper examines multi‐decadal trends in DIN and DIP concentrations and loads, and their relationships to climatic and hydrologic factors (e.g., stream and air temperature, discharge, precipitation) in the PNW. Dissolved constituents act as a broad sentinel of linkages between watershed and in‐stream mechanisms such as nitrification, denitrification, nutrient use efficiency, evapotranspiration, hydrologic connectivity, groundwater extraction, irrigation, and land uses. As opposed to the total N and P often used in individual, autochthonous, lentic systems, DIN and DIP are used here as measures of multiscaled processes in allochthonous lotic systems with diverse flow paths. Time‐series data from public agencies were used for up to 20 years in river outlets from the Willamette, Salmon, Spokane, and Yakima watersheds. Seasonal Mann Kendall (SMK) tests suggest significant decreasing multi‐decadal trends in DIN and DIP loads for three out of four watersheds (for DIN, SMK = −0.104; for DIP, SMK = −0.081, −0.181, and −0.213), significant decreasing trends in DIN concentrations for one of the four watersheds (SMK = −0.144), and significant decreasing trends in DIP concentrations in three of the four watersheds (SMK = −0.120, −0.135, and −0.157). Multivariate regressions found significant relationships for concentrations, loads, and ratios when regressed against stream and air temperatures, precipitation, and discharge (16 significant regressions, with adjusted R2 values between 0.016 and 0.65). Highlights of these regression results are as follows: (1) precipitation, discharge, and water and air temperatures help to explain DIN and DIP concentrations and loads, (2) changes in DIN concentrations are sensitive to more hydroclimatic variables than DIP concentrations, and (3) DIP concentrations are positively correlated with stream temperature while DIP loads are negatively correlated with stream temperature. Furthermore, seasonal changes in nutrients — and their potential to alter aquatic productivity during a year — has received little attention in the literature. Regressions established significant seasonality or monthly variation of DIN and DIP concentrations and loads in all four watersheds (20 significant regressions, with adjusted R2 values between 0.038–0.65). Nutrient thresholds of DIN (0.3–0.5 mg/L) and DIP (0.05–0.005 mg/L) concentrations were used to analyze N‐ and P‐limitation. P‐limitation is known to occur in lakes, and N‐limitation is known to occur in rivers. Surprisingly, except for one watershed (Salmon), nutrient concentrations for both DIN and DIP in all watersheds were shown to be above the limitation thresholds across multiple seasons. In certain situations, such as where significant decreasing trends continue, the DIN:DIP ratio suggests seasonal switching between N‐ and P‐limited could create ideal conditions for HABs. The findings of this study have important implications for water resource management issues such as agriculture, land use development, fish populations, timber harvests, water quality, and public health.
... In the studies of the combined effects of climate and land-use change, very few studies simultaneously consider the combined effects on runoff, sediment, and nutrient loads. Instead, most studies consider the effects either on hydrology (Chanapathi and Thatikonda, 2020;Dosdogru et al., 2020), or on hydrology and sediment (Khoi and Suetsugi, 2014;Zuo et al., 2016;Ndulue and Mbajiorgu, 2018), or on hydrology and nutrient load (Chen et al., 2017;Molina-Navarro et al., 2018;Shrestha et al., 2018) only. However, both runoff and sediment decide the transport process of nutrient loading (Tang et al., 2018). ...
... Molina- Navarro et al., 2018; Schürz et al., 2018). Eight GCMs corresponding to the two emission scenarios RCP4.5 (CMCC-CMS, GFDL-ESM2G, IPSL-CM5A-LR, and MPI-ESM-LR) and RCP8.5 (BCC-CSM1-1-m, CanESM2, MIROC-ESM, and MRI-CGCM3) are adopted by using 10 and 90% quantiles of the change of average rainfall and temperature in the future predicted by each GCM relative to the baseline period (Immerzeel et al., 2013) (Figure 2). ...
The present study predicts and assesses the individual, combined, and synergistic effect of land-use change and climate change on streamflow, sediment, and total phosphorus (TP) loads under the present and future scenarios by using the Soil and Water Assessment Tool (SWAT). To predict the impacts of climate and land-use change on streamflow, sediment, and TP loads, there are 46 scenarios composed of historical climate, baseline period climate, eight climate models of Coupled Model Intercomparison Project phase 5 (CMIP5) of two representative emission pathways (RCP4.5 and RCP8.5), after downscaled and bias-corrected, two observed land-use maps (LULC 1995, LULC 2015) and the projected two future land-use maps (LU2055 and LU 2075) with the help of CA-Markov model to be fed into SWAT. The central tendency of streamflow, sediment, and TP loads under future scenarios is represented using the annual average. The intra-/inter-annual variation of streamflow, sediment, and TP loads simulated by SWAT is also analyzed using the coefficient of variation. The results show that future land-use change has a negligible impact on annual streamflow, sediment, TP loads, and intra-annual and inter-annual variation. Climate change is likely to amplify the annual streamflow and sediment and reduce the annual TP loads, which is also expected to reduce its inter-/intra-annual variation of TP loads compared with the baseline period (2000–2019). The combined impact of land-use and climate change on streamflow, sediment, and TP loads is greater than the sum of individual impacts for climate change and land-use change, especially for TP loads. Moreover, the synergistic impact caused by the interaction of climate and land use varies with variables and is more significant for TP loads. Thus, it is necessary to consider the combined climate and land-use change scenarios in future climate change studies due to the non-negligible synergistic impact, especially for TP loads. This research rare integrates the individual/combined/synergistic impact of land-use and climate change on streamflow, sediment, and TP loads and will help to understand the interaction between climate and land-use and take effective climate change mitigation policy and land-use management policy to mitigate the non-point source pollution in the future.
... The impact of land use type, topography, climate change, soil type, agriculture management, and other factors that affect NPS pollutant loads has often been investigated using hydrologic and water quality models (Fereidoon and Koch 2018;Molina-Navarro et al. 2018;Nasab et al. 2017 Pesce et al. 2018;Stefanidis et al. 2016;Wang et al. 2018a;Yu et al. 2018;Zou et al. 2018). These studies indicate that landscape patterns greatly influence NPS pollution (Boongaling et al. 2018). ...
... As the study area is located in a mountain-rural region lacking of monitored data for water quality, only the data for 1995 and 1996 were available and used for calibration and validation of sediment flux and ammonia nitrogen. The calibration and validation effectiveness were evaluated via three indices, i.e., coefficient of determination (R 2 ), Nash-Sutcliffe efficiency (E NS ), and relative error (E R ) (Molina-Navarro et al. 2018;Nash and Sutcliffe 1970;Wang et al. 2018c;Yu et al. 2018). ...
Landscape patterns have a substantial effect on non-point source (NPS) pollution in watersheds. Facilitating sustainable development of mountain-rural areas is a major priority for China. Knowledge of the impacts of various landscapes on water quality in these areas is critical to meeting environmental goals. This study applied the Soil and Water Assessment Tool (SWAT) to create a hydrologic and water quality model of the study watershed; then, the relationship between water quality and landscape patterns was investigated using multiple linear regression and redundancy analysis. The results show that the western sub-basins had higher nitrogen pollution loads, and the total nitrogen concentration reached a maximum value of 3.91 mg/L; the eastern sub-basins had a higher pollution load of phosphorous featured by maximum total phosphorous concentration of 2.15 mg/L. The water quality of the entire watershed in all scenarios tended to deteriorate over time. Landscape metrics accounted for 81.7% of the total variation in pollutant indicators. The percentage of forest landscape was negatively correlated with NPS pollution, while other types of landscape showed a positive correlation. The patch density, landscape shape index, and largest patch index of urban and agricultural lands were negatively correlated with pollutant concentrations. Upland landscapes contributed more pollutants than paddy fields. Some measures, e.g., returning grassland and farmland to forest in steep regions and replacing upland crops with paddy fields, were recommended for mitigating NPS pollution in the study watershed.
... This study was motivated by a lack of knowledge and the need for better modelling approaches to assess spatiotemporal changes in nutrient and suspended solids (SS) status in a peatland-dominated catchment. The soil and water assessment tool (SWAT) has been successfully implemented under various conditions (Molina-Navarro et al. 2017), including in peatlands (Melaku et al. 2020). However, to our knowledge, it has not yet been used in drained peatlands, especially in areas with intensive peatland forestry. ...
Peatland drainage can affect the natural state of hydrological conditions and nutrient loading but is rarely included in catchment-scale models. To understand the gap, we aimed to use the soil and water assessment tool (SWAT) model to observe drained peatlands and their properties to predict nutrients and suspended solids (SS) in the peatland-dominated Simojoki catchment. We integrated drainage networks in SWAT to (i) identify the parameters for the drainage; (ii) determine annual loads and mean concentrations of SS, organic phosphorus (Org-P), total phosphorus (TP), organic nitrogen (Org-N), and total nitrogen (TN); (iii) understand spatial variation of nutrients and SS; and (iv) investigate the uncertainty ranges for the estimates. The calibrated SWAT model showed a 9.6% PBIAS between the simulated flow and the observations with low to medium loading variations for the water quality parameters. For Org-N and TN, the highest loading per year was at the downstream outlet, whereas for SS, Org-P, and TP, it was higher at the upstream outlet of the catchment. This approach of representing the drained peatland in SWAT indicated a maximum spatial distributed load in the peat soil in the clear-cut area and it can be beneficial in future hydrological modelling efforts in identifying the status of nutrients or SS.
... Quantitative, process-based models are widely used for assessing the combined effects of climate and /land cover change (e.g. Moe et al. 2019;Whitehead et al. 2013;Bussi et al. 2016;Molina-Navarro et al. 2018) on catchment processes. The results have provided an important source of information to decision-makers for estimating the impact of land management alternatives on water quality. ...
Browning of surface waters due to increased terrestrial loading of dissolved organic matter (DOM) is observed across the Northern Hemisphere. The effects influence several ecosystem services from freshwater productivity to water purification. Brownification is often explained by changes in large-scale anthropogenic pressures and ecosystem functioning (acidification, climate change, and land cover changes). This study examined the effect of forest use changes on water browning in Finland, considering the effects of global pressures. Our goal was to find the ecosystems and geographic areas that are most sensitive to environmental pressures that increase the loading of DOM. We were also looking for land use strategies that decrease browning. We combined mathematical watershed modelling to scenarios of climate change, atmospheric deposition, and forest use change. Changes included scenarios of forest harvest and protection on forest, that were derived from European Union’s regulation. The study area covered 20 watersheds from south to north of Finland. In northern Finland brownification continue. In southern Finland global influence (atmospheric deposition, climate change) seem to weaken, giving more space for local forest use change having an influence on brownification. Forest use change was more influential in river basins dominated by organic soils than in mineral soils. Extending forest protection decreased brownification especially in areas where the influence of atmospheric pressure is decreasing. When forest protection is planned to provide a carbon storage and sequestration potential and to favor biodiversity, it has favorable effect on surface water quality as well.
... Coastal marine waters assume a vital role in the ecological ecosystem balance due to their high productivity and their crucial function in the major biogeochemical processes in the marine environment (McLaughlin et al. 2021). In addition to their role as a buffer space, between land and the deep sea, their transient position exposes them to several discharges from human activities such as industry and agriculture, which are in severe increase due to global changes (Molina-Navarro et al. 2018;Ontoria et al. 2019). ...
To evaluate the impact of anthropogenic activities and climate change on the water quality of Monastir Bay, monthly monitoring of physico-chemical and bacteriological parameters was conducted out in eight stations located in the southern part of the coastal waters during 2019. The obtained results showed severe fluctuations, both spatially and temporally, in temperature (from 9 °C to 33 °C), salinity (between 37.9 and 45.9 practical salinity units (psu), turbidity (between 0.18 and 8.5 nephelometric turbidity units (NTU), and pH (8.11 and 9.15). Oxygenation is quite variable, with total or partial anoxia recorded in certain areas of the bay, especially in the end of spring and in summer. Organic nitrogen and phosphorus concentrations were significantly higher in the North Bay than in the South. Mineral nitrogen at most stations was dominated by ammonium, indicating an imbalance in the nitrogen cycle. Chlorophyll a concentrations were above 20 µg/L in some stations, with two peaks, one in spring and a second in autumn. The bacteriological analysis showed a predominance of salt-tolerant bacteria and the presence of fecal contamination, especially near urban wastewater discharge zones. Analysis of variance confirms that this ecosystem is strongly influenced by anthropogenic inputs. The trophic index shows that more than 30% of the samples analyzed correspond to eutrophic waters. The high anthropogenic inputs combined with the limited current are responsible for the degradation of this ecosystem. The results obtained in this study constitute a database for the development of an ecological restoration strategy.
... Hydrological models are widely used to support the management of water resources, including the assessment of scenario impacts (Hakala et al., 2019;Molina-Navarro et al., 2018). The model's process representation, its limitations, assumptions made by the modeller, and other factors such as calibration procedures contribute to uncertainty in model predictions (Goderniaux et al., 2015;Hakala et al., 2019;Karlsson et al., 2016;Mendoza et al., 2015;Smerdon, 2017). ...
... Cho et al., 2016;Huttunen et al., 2015;Marcinkowski et al., 2017;Merriman et al., 2019;Molina-Navarro et al., 2018;Ockenden et al., 2016;Orlińska- Woźniak et al., 2020;Shi & Huang, 2021;Tattari et al., 2017) ...
Currently, climate change is considered as an important factor affecting nutrient loads introduced through riverine systems into the Baltic Sea. Although the prospect of a large increase in pollution has long seemed very real, it still does not translate into planning of effective remedial actions. One of the factors limiting the development of such activities is the scale of simulations, focusing generally on catchment outlet profiles. To fill this gap and enable a step forward in understanding responses toward future predictions in a higher resolution scale (subcatchment), we assessed nutrient load contribution using calculation profiles localized along a main watercourse and its tributaries. To track spatial and seasonal changes of total nitrogen and phosphorus for the Wełna River (central Poland), we used climate change data and the SWAT model. Having at our disposal a catchment model with a good performance we could follow not only total load changes in particular subcatchments, but also track localization of the pollution sources and their direct impact on load estimations. Our results showed an increase of the loads, especially from the agricultural land use type, up to 34% for TN and 85% for TP, in the most extreme scenario. Moreover, forest areas have been noted as highly reactive to climate change, and through their localisation are able to distinctly alter nutrient outflow. Finally, the contribution of urban areas should be further investigated since the dynamics of nitrogen and phosphorus release from impervious surfaces is noticeably different here than from the other diffuse sources.
... A substantial volume of research has been dedicated to the development, application, and enhancement of P source apportionment models (Ren et al., 2022a(Ren et al., , 2023Zou et al., 2020). The primary source apportionment models include inventory analysis, diffusion models, and receptor models (Molina-Navarro et al., 2018;Ren et al., 2023;Zou et al., 2020). These models are capable of simulating watershed hydrological processes across various scales and situations, enabling the estimation of pollution source contributions (Chen et al., 2019;Wang et al., 2018a;Zhu et al., 2023). ...
... In fact, areas with natural cover such as forests, wetlands, and riparian areas help maintain good quality freshwater sources (Ernst et al. 2004;Cunha et al. 2016). Conversely, in areas with intensive agriculture, there is a high level of non-point pollution of nutrients and pesticides (Molina-Navarro et al. 2018). In addition, both agriculture and urbanization play a role in the presence of microbiological agents and chemicals (G1) in raw water sources (Rousseau et al. 2004;Yu et al. 2014;Jalliffier-verne 2015;Cunha et al. 2016). ...
Climate change (CC) causes extreme meteorological events such as floods, droughts, water scarcity, heat waves, wildfires, and extreme cold. CC may also damage public infrastructures such as drinking water systems (DWSs) and reduce water quality from source to tap. The objective of this review paper is to provide a critical analysis of (1) the impact of CC on the three components of the DWSs: source, treatment, and distribution; (2) the perspectives of DWS employees on CC impacts and adaptation solutions for maintaining water quality; and (3) decision support systems (DSSs) that could be used by DWS employees for CC adaptation. A bibliographic research was conducted using international databases and search engines. The search for scientific articles resulted in the selection of 5234 articles, 78 of which were analyzed in more detail for the elaboration of this scoping review. This review shows that the impacts of CC on water quality are significant, but DWS employees are not enthusiastic about developing adaption measures. This review also shows that DSSs can help DWS employees facilitate the CC adaptation process for the protection of source water, improve water treatment plant operations, and enhance routine management of water quality in the distribution system. Further research is needed to identify strategies that might increase the awareness of and interest in climate change impacts, adaptation, and the use of DSSs among DWS employees.
... Because NBP 3 and 5 had a higher ratio of biomass removal in the catchment, the export of nutrients and SS was also higher in those NBPs. A similar analysis was also applicable for organic and inorganic nutrients, where organic nutrients were the major drivers throughout the catchment, which varied in the same way as total nutrients 43 . ...
The Nordic Bioeconomy Pathways (NBPs), conceptualized subsets of Shared Socioeconomic Pathways varying from environmentally friendly to open-market competition scenarios, can lead to plausible stressors in future for using bioresources. This study analysed the impacts of NBPs on hydrology and water quality based on two different land system management attributes: management strategy and a combination of reduced stand management and biomass removal at a catchment-scale projection. To understand the potential impacts of NBPs, the Simojoki catchment in northern Finland was chosen, as the catchment mainly covered peatland forestry. The analysis integrated a stakeholder-driven questionnaire, the Finnish Forest dynamics model, and Soil and Water Assessment Tool to build NBP scenarios, including Greenhouse gas emission pathways, for multiple management attributes to simulate flows, nutrients, and suspended solids (SS). For the catchment management strategy, an annual decrease in nutrients was observed for sustainability and business-as-usual scenarios. Reduced stand management and biomass removal also led to decreased export of nutrients and SS for the same scenarios, whereas, in other NBPs, the export of nutrients and SS increased with decreased evapotranspiration. Although the study was investigated at a local scale, based on the current political and socioeconomic situation, the approach used in this study can be outscaled to assess the use of forest and other bioresources in similar catchments.
... Quantitative, process-based models are widely used to assess combined effects of climate and land use change (e.g., Moe et al., 2019;Whitehead et al., 2013;Bussi et al., 2016;Molina-Navarro et al., 2018) on catchment processes. Different catchment-scale, process-based models have been applied in the Nordic countries to estimate impact of land use and land management on water quality (e.g. ...
In Northern Finland, the most significant land use challenges are related to bioenergy production from peat extraction and forest biomass. Increasing societal demand for bioenergy may increase production rates. However, environmental impacts of peat extraction are of increasing concern, which has led to a decline in production, thereby freeing up these areas for other uses. Using storylines for different societal futures and process-based models (PERSiST and INCA), we simulated the effect of simultaneous land use change and climate change on
water quality (phosphorus, nitrogen and suspended sediments concentration). Conversion of peat extraction areas to arable land, together with climate change, may pose a risk for deterioration of ecological status. On the other hand, continuous forestry may have positive impacts on water quality. Suspended sediment concentrations in the river do not exceed water quality requirements for salmonids, but nitrogen concentrations may exceed threshold values especially during high flows. A storyline emphasizing sustainable development in energy production led to the best outcome in terms of water protection.
... The individual models have been applied in other studies, e.g., as part of the monitoring of the environment in Denmark [81][82][83], but only a modeling chain such as the DEEMON system allows for a consistent evaluation from management regulation to environmental effects. In the following, we discuss the main underlying assumptions and uncertainties related to the model chain and the scenarios. ...
Manure acidification has been introduced as an abatement to reduce ammonia (NH3) emissions to improve air quality and protect terrestrial and aquatic environments from nitrogen deposition. A successful regulation of NH3 emissions using manure acidification might, however, result in increased nitrogen leaching from fertilized fields with adverse effects on freshwater and marine ecosystems, if the overall fertilizer application rate in the fields is not adjusted according to the increased fertilizer value of the manure. We apply a holistic model framework encapsulating all important environmental compartments to assess the ecological and economic consequences of a specific agricultural practice or a combination of these. The results show that manure acidification combined with air cleaners reduces NH3 emission and atmospheric nitrogen deposition with substantial positive effects on the terrestrial environment. Although manure acidification results in a slight increase in total nitrogen input into freshwater and marine ecosystems, the subsequent increase in chlorophyll a concentration and decrease in water transparency is insignificant. Hence, according to the model results, manure acidification will improve terrestrial nature quality, with no significant adverse effects on the aquatic environments.
... Land use largely represents land management practices such as fertiliser dosage, irrigation, and crop and tree species . Some land-use conversions, such as crop plantations after the deforestation of broad-leaved forests, can increase both above-and below-ground N loads (Molina-Navarro et al., 2018;Mulholland et al., 2008). Liang et al. (2021) found that land management practices are crucial factors that influence SON leaching. ...
Accumulation of soluble organic nitrogen (SON) in soil poses a significant threat to groundwater quality and plays an important role in regulating the global nitrogen cycle; however, most related studies have focused only on the upper 100-cm soil layers. Surface land-use management and soil properties may affect the vertical distribution of SON; however, their influence is poorly understood in deep soil layers. Therefore, this study assessed the response of SON concentration, pattern, and storage in deep regoliths to land-use conversion from woodlands to orchards in a subtropical hilly region. Our results showed that the SON stocks of the entire soil profile (up to 19.5 m) ranged from 254.5 kg N ha−1 to 664.1 kg N ha−1. Land-use conversion not only reshaped the distribution pattern of SON, but also resulted in substantial accumulation of SON at the 0–200 cm soil profile in the orchards compared to that in the woodlands (124.1 vs 190.5 kg N ha−1). Land-use conversion also altered the SON/total dissolved nitrogen ratio throughout the regolith profile, resulting in a relatively low (<50 %) ratio in orchard soils below 200 cm. Overall, 76.8 % of SON (338.4 ± 162.0 kg N ha−1) was stored in the layers from 100 cm below the surface to the bedrock. Regolith depth (r = −0.52 and p < 0.05) was found to be significantly correlated with SON concentration, explaining 17.8 % of the variation in SON, followed by total nitrogen (14.4 %), total organic carbon/total nitrogen ratio (10.1 %), and bulk density (9.3 %). This study provides insights into the estimation of terrestrial nitrogen and guidance for mitigation of groundwater contamination risk due to deep accumulation of SON.
... The popularity of topics such as movement, drinking water and fisheries has decreased, while that of the other topics, such as heavy metal, gas fluxes, spatiotemporal trends, landuse change, eutrophication and climate change, has grown considerably. For example, starting at the bottom of the list before the Similarly, Molina-Navarro et al. (2018) illustrated that the nutrient loads of rivers largely depend on land use management in interaction with climate change. What is striking is that microbial and antibiotic resistance have never been a major research topic to most river researchers as they have stayed on the lowest ranks ever since. ...
As one of the earth's key ecosystems, rivers have been intensively studied and modelled through the application of machine learning (ML). With the amount of large data available, these computer algorithms are ever increasing in numerous fields, although there is ongoing scepticism and scholars still question the actual impact and deliverables of algorithms.
This study aims to provide a systematic review of the state‐of‐the‐art ML‐based techniques, trends, opportunities and challenges in river research by applying text mining and automated content analysis.
Unsupervised and supervised learning have dominated river research while neural networks and deep learning have also gradually gained popularity. Matrix factorisation and linear models have been the most popular ML algorithms, with around 1300 and 800 publications on these topics in 2020 respectively. In contrast, river researchers have had few applications in multiclass and multilabel algorithm, associate rule and Naïve Bayes.
The current article proposes an end‐to‐end workflow of ML applications in river research in order to tackle major ML challenges, including four steps: (1) data collection and preparation; (2) model evaluation and selection; (3) model application; and (4) feedback loops. Within this workflow, river modellers have to balance numerous trade‐offs related to model traits, such as complexity, accuracy, interpretability, bias, data privacy and accessibility and spatial and temporal scales. Any choices made when balancing the trade‐offs can lead to different model outcomes affecting the final applications. Hence, it is necessary to carefully consider and specify modelling goals, understand the data collected and maintain feedback loops in order to continuously improve model performance and eventually reach the research objectives. Moreover, it remains crucial to address the users' needs and demands that often entail additional elements, such as computational cost, development time and the quantity, quality and compatibility of data. Furthermore, river researchers should account for new technologies and regulations in data collection and protection that are transforming the development and applications of ML, most notably data warehouse and information management with multiple‐cycles that are becoming a cornerstone of the integration of ML in decision‐making in river and ecosystem management.
... Water resources are subject to multiple stressors, of which climate change is a major factor that significantly affects the hydrological cycle by influencing precipitation, temperature, and evaporation processes, thereby leading to changes in biogeochemical processes that control the transformation and transportation of pollutant (Huang et al., 2015;Li et al., 2021;Rudra et al., 2020). Climate change, on the one hand, may impede the achievement of water quality goals by increasing pollutant losses, and an example is the nitrogen mineralization rate is positively correlated with temperature (Costa et al., 2020;Molina-Navarro et al., 2018;Plunge et al., 2022); on the other hand, it adds uncertainty to watershed management by altering NPS pollution patterns and resulting in substantial changes in the priority areas (i.e., CSAs) for applying BMPs. However, recent studies suggest that integrating climate change into watershed management (Brouziyne et al., 2018;Plunge et al., 2022;Qiu et al., 2020;Wallace et al., 2017) and developing long-term resilient watershed management that can buffer climate change impacts on aquatic systems is a promising approach (Bosch et al., 2018). ...
Simulation-based optimization (S–O) frameworks are effective in developing cost-effective watershed management strategies, where optimization algorithms have substantial effect on the quality of strategies. Despite the development and improvement of multi-objective evolutionary algorithms (MOEAs) provide more robust alternatives for optimization, they typically have limited applications in real-world decision contexts. In this study, three advanced MOEAs, including NSGA-II, MOEA/D and NSGA-III, were introduced into the S–O framework and applied to a real-world watershed management problem, and their performance and characteristics were quantified through performance metrics. Results show that a higher crossover or mutation probability do not necessarily promote convergence and diversity of solutions, while a larger generation and population size is helpful for MOEAs to find high-quality solutions. Compared to the other two MOEAs, NSGA-II consistently exhibits robust performance in finding solutions with good convergence and high diversity, and provides more options at the same computational cost, while the degenerate Pareto front of the proposed watershed management problem may account for the poor performance of MOEA/D and NSGA-III in terms of diversity. For a 10% TN or TP reduction target, the average cost of the NSGA-II optimized strategies is 32.22% or 47.83% of the commonly used strategies. In addition, this study also discussed the development of resilient watershed management to buffer the impacts of climate change on aquatic system, the incorporation of fuzzy programming into the S–O framework to develop robust watershed management strategies under uncertainty, and the application of machine learning-based surrogate models to reduce computational cost of the S–O framework. These results can contribute to the understanding of MOEAs and provide useful guidance to decision makers.
... The mathematical modeling of water quality at the watershed level has been developed through the implementation of models that represent physical processes (Gong et al. 2019;Hoghooghi et al. 2021;Hou et al. 2021;Li et al. 2021) as well as by the application of statistical models that seek to identify patterns between predictive variables and quality parameters (Zampella et al. 2007;Park et al. 2014;Giri and Qiu 2016a). Despite the important use of physical or process-based models (Cunwen et al. 2011;Almeida et al. 2018;Molina-Navarro et al. 2018), it should be noted that they generally include many parameters that must be calibrated and require continuous series of hydrometeorological and water quality information over time, which is not always available. For example, Hesse et al. (2013) mention that by increasing the complexity in the representation of nutrient retention processes in a model, the number of calibration parameters, time requirements, and simulation uncertainties also increase. ...
A better understanding of diffuse pollution processes distressing surface water bodies is relevant to develop actions focused on the sustainable management of water resources. This research aims to identify relevant watershed variables that explain the spatial variability patterns of surface water quality in lotic mountain water bodies. Twenty-eight candidate variables (10 land cover and land use (LCLU), 6 pedo-topographic (PT), and 12 hydrometeorological (HM)) were defined to explain the concentration of six water quality parameters temperature (T), pH, dissolved oxygen (DO), chemical oxygen demand (COD), electrical conductivity (EC), and nitrates (NO3-)) in 76 surface water streams of the Andina region, Colombia. The selection of the explanatory variables was carried out by applying an iterative input selection (IIS) algorithm based on highly randomized tree models. The results show that the variability in the concentration of each water quality parameter is explained by a combination of LCLU, HM, and PT variables. LCLU was the most important group of explanatory variables in the selection, followed by HM variables group. This is not the case for DO, where the HM variables show the highest importance. In all the implemented models, the PT variables showed the lowest incidence. This research developed a success approach for identifying basin variables able to contribute to understand non-point sources of pollution, and thus it was not oriented to create a predictive model of water quality, but rather to use machine learning modeling to expose probable relationships between watershed attributes and the quality of surface water. These results can support other water quality studies and territorial planning instruments on the role of watershed-scale variables in diffuse pollution processes in surface water bodies. The implemented algorithm provided modeling flexibility, computational efficiency, and minimum redundancy, allowing a reasonable representation of the observational data set.
... Although there are uncertainties in measuring and predicting the impact of farmland and agricultural activities, we have learned unequivocally that agricultural production does lead to an increase in nutrients in the region's waters, thereby accelerating eutrophication in the waters. Excessive application of chemical fertilizers and pesticides can also be harmful to water quality; for instance, the increase of pesticide and fertilizer application was associated with the increase of nutrient emissions and the extinction of underwater aquatic vegetation in the Mississippi River (Turner and Rabalais 1991), the Chesapeake Bay Basin (Boynton et al. 1982;Kemp et al. 1983), the Odense Fjord catchment (Molina-Navarro et al. 2018), and the Chaohu lake basin (Yang et al. 2020). In 1981, British scholar OAKES et al. explored and studied the distribution of solute extracted from farmland in major aquifers in the UK from 1975 to 1980 and concluded that nitrate concentration was significantly correlated with agricultural production practices (Oakes et al. 1981). ...
Good surface water quality is critical to human health and ecology. Land use determines the surface water heat and material balance, which cause climate change and affect water quality. There are many factors affecting water quality degradation, and the process of influence is complex. As rivers, lakes, and other water bodies are used as environmental receiving carriers, evaluating and quantifying how impacts occur between land use types and surface water quality is extremely important. Based on the summary of published studies, we can see that (1) land use for agricultural and construction has a negative impact on surface water quality, while woodland use has a certain degree of improvement on surface water quality; (2) statistical methods used in relevant research mainly include correlation analysis, regression analysis, redundancy analysis, etc. Different methods have their own advantages and limitations; (3) in recent years, remote sensing monitoring technology has developed rapidly, and has developed into an effective tool for comprehensive water quality assessment and management. However, the increase in spatial resolution of remote sensing data has been accompanied by a surge in data volume, which has caused difficulties in information interpretation and other aspects.
... Odense Fjord is located on the Funen Island, Denmark. Funen has an oceanic climate with an annual average temperature of 8.7 • C (2000-2010) and an annual average precipitation of 812 mm (Molina-Navarro et al., 2018). Odense Fjord consists of two parts: the inner part with an average water depth of about 0.8 m and the outer part with an average water depth of 2.7 m (Riisgård et al., 2007). ...
As part of Blue Carbon ecosystems (BCEs), detached macrophytes can be transported to the coast due to current and wave actions, and then deposited on the shore as beach wrack. To date, the role of beach wrack in the material cycle in BCEs is still unclear. In order to track the fate of beach wrack, this study conducted a monitoring survey on a semi-sheltered beach in Odense Fjord (Denmark) using camera trap data. Deep learning with a VGG network architecture was used to classify the image dataset acquired by the camera trap. The VGG network demonstrated the capability to identify beach wrack from different beach scenes, and the method can provide results on large datasets within a short time (187 images analyzed within 5 min) compared to manual identification of images. By combining the VGG detection with color-based segmentation, beach wrack coverage was determined. To evaluate the impact of ambient conditions on wrack deposition on the shore and relocation back to the sea, wind (including speed and direction), water temperature, and tidal amplitude were analyzed as environmental variables. Partial least squares regression (PLSR) analysis revealed that micro-tidal action with an average amplitude of 0.41 m accelerated the movement of floating macrophytes between the shore and the sea. Despite being exposed to the prevailing southwesterly winds (average speed of 11 m/s), the beach was sheltered due to the location in the inner part of Odense Fjord, limiting the transport of drifting macrophytes from sea to the shore. By using the camera trap to conduct continuous monitoring, this study presents a labor-saving and practical approach to track the dynamics of detached macrophytes deposited on the shore. Furthermore, the application of deep learning in image identification provides a study case for using a large image dataset to assist in ecological studies of dynamic environments.
... Land-use intensification increases the use of fertilizers, causing accelerated eutrophication of streams and particularly so in lowland areas (Howden et al., 2007;Sabater et al., 2018a). Furthermore, the runoff of nutrients and solids to the streams may accelerate because of higher precipitation, and concentrations may increase under drought (Aznarez et al., 2021;IPCC et al., 2014;Jeppesen et al., 2009;Molina-Navarro et al., 2018;Sabater et al., 2018b;Seneviratne et al., 2012). Land-use intensification may further favour the deforestation of riparian vegetation, thus affecting their ability to buffer runoff as well as to modulate light and temperature conditions within the streams (Sweeney et al., 2004;Turunen et al., 2021). ...
Climate-induced changes in precipitation and land-use intensification affect the discharge of streams worldwide, which, together with eutrophication and loss of riparian canopy, can affect periphyton biomass and composition, and therefore, ultimately the stream functioning. We investigated the responses of periphyton biomass and life-forms (i.e., high profile, low profile and motile) to these changes applying an experimental approach by modulating nutrients (nutrient diffusion substrates enriched with 0.5 M NH4NO3 + 0.031 M KH2PO4 and without nutrient enrichment) and light availability (50% shade and full light) along a gradient in discharge ranging from 0.46 to 3.89 L/s (0.7 to 6.5 cm/s) in twelve large-sized (12- m long) outdoor flumes resembling lowland streams. We also analysed the potential effects of other environmental variables including macroinvertebrates on the responses of periphyton to discharge, nutrients, and light. Light and nutrient availability drastically affected periphyton biomass and composition responses to discharge. Periphyton biomass decreased with increasing discharge when shaded but this did not happen when exposed to full light. Under full light conditions, nutrient enrichment mediated an increase in the periphyton biomass with increasing discharge, possibly reflecting an increased metabolism, but this did not happen under non-enriched conditions. Enrichment further affected the compositional responses of periphyton to discharge, with an increase in the biomass of motile, fast-growing, small-sized flagellated at low discharge conditions, and mitigating a loss of high profile periphyton under higher discharges. Light did not affect periphyton composition, and the abundance or feeding-group composition of the macroinvertebrates did not affect biomass or composition of the periphyton either. Our results suggest that nutrient enrichment and light play an important synergistic role in the responses of the periphyton biomass and composition to discharge and emphasize the relevance of riparian canopy conservation and eutrophication control to avoid periphyton growth under increased discharge scenarios in small lowland streams.
... As organic fertilizers cause less pollution than inorganic fertilizers, increasing the usage of organic fertilizers, reducing the usage of chemical fertilizers, and improving the utilization of fertilizers can effectively reduce nonpoint source pollution from rice paddies (Sun et al. 2012). In addition to fertilizer dosage, fertilization and tillage methods, irrigation water dosage, the compound form, and organic component ratio of phosphorus in fertilizer will all have an impact on phosphorus loss (Hart et al. 2004;Mander et al. 1998;Molina-Navarro et al. 2018;Xu et al. 2020). In residential and forest areas, phosphorus loading also requires attention in heavy precipitation event. ...
Phosphorus is an essential nutrient for maintaining and increasing crop production. Owing to frequent human activities, phosphorus resources cause serious environmental pollution. Simulating phosphorus transport with a hydrological model could help understand the phosphorus loss processes at catchment scale. However, in previous modeling studies, phosphorus calibration and validation usually run in monthly time steps, it is difficult to correctly simulate the phosphorus transport peak. Additionally, most previous studies have disregarded the form of phosphorus in transported processes and only considered the total phosphorus, which cannot accurately assist in understanding the specific process of phosphorus transport. Rice is an important agricultural product, widely planted in Asia, and the particulate inorganic phosphorus loss in rice paddies is generally high. Previous studies could not fully simulate the transport of different phosphorus forms in rice paddy catchments. We analyzed the impact of climate change on phosphorus transport under different fertilization scenarios using the Soil and Water Assessment Tool. We compared mineral phosphorus flux with the sum of particulate phosphorus and dissolved orthophosphate during the calibration and validation processes. The Nash–Sutcliffe efficiencies of mineral and total phosphorus in both the calibration and validation periods were higher than 0.65. Rice paddies are the major source of phosphorus loss from the catchment, amounting to 5.4 kg/ha, and particulate inorganic phosphorus accounted for 53% of total phosphorus loss. The average annual phosphorus export was 30 tons/yr; the maximum value was nine times higher than the minimum value. Precipitation had a clear impact on phosphorus transport.Graphic Abstract
... Varanou et al. (2002) also reported that decreasing surface and lateral flows diminished nitrate losses in the Ali Efenti Basin, central Greece. Our analysis illustrated that the highest increase in temperature is projected for summer under the two RCPs, and the large decrease in nitrate estimates occurs in the summer months because of the increase in temperature, which could also lead to more losses of nitrate due to the increase of mineralization (Molina-Navarro et al., 2018). ...
The spatial and temporal dimensions of environmental impacts of climate and land cover changes are two significant factors altering hydrological processes. Studying the effects of these factors on water quality, provides important insight for water resource management and optimizing land planning given increasing water scarcity and water pollution. The impact of land cover and climate changes on surface water quality was assessed for the Neka River basin in Northern Iran. The widely used Soil and Water Assessment Tool (SWAT) was applied for pollutant modeling, and was calibrated using the Sequential Uncertainty Fitting (SUFI-2) algorithm. An ensemble of 17 CMIP5 climate models under two IPCC greenhouse gas emission scenarios were selected, and future land cover change (LCC) was modeled based on the evolution that occurred in the last decades. We simulated the impacts of climate change (CC) and LCC on sediment, nitrate, and phosphate for the 2035–2065 time slice. The annual loads of sediment, phosphate, and nitrate are projected to decrease under both CC scenarios based on the inter-model average, and generally follow a pattern similar to the change in river discharge. Nitrate concentrations show an increase across all seasons, while the sediment and phosphate concentrations increase in winter and autumn under CC conditions. Results indicate that pollutants are expected to increase under LCC alone, mainly due to the expansion of the cultivated areas. Overall, it seems CC has a greater impact than LCC on the variation of water quality variables in the Neka River basin. With a combined change in climate and land cover, the annual nitrate concentrations are expected to increase by + 19.7% and + 17.9%, under RCP 4.5 and RCP 8.5, respectively. The combined impacts of the CC and LCC caused a decline in the annual sediment and phosphate concentrations by −10.1% and −2.2% under RCP 4.5 and −9%, and −3.2% under RCP 8.5, respectively.
... The SWAT (Arnold et al., 1998) has been recognized as an essential tool for evaluating hydrologic effects (Gassman et al., 2007;Anand et al., 2018c). The SWAT model has been extensively applied for the simulation and assessment of the several influences of the alterations in climatic conditions and transformation of land use upon the hydrologic components of the catchment (Molina-Navarro et al., 2018;Reshmidevi et al., 2018). Therefore, it has been adopted in this research to study the effects of alterations in climatic conditions as well as conceivable transformations in the future land use on the existing water resources in the Ganga river system, India. ...
The assessment of climate and land-use transformations upon the hydrologic response is crucial for decision-makers to accomplish various adaptation strategies. The Regional Climate Models (RCMs) have been extensively employed to study the impact of climate change on various hydrologic components. However, these climate models are subjected to a large number of uncertainties, which demands a careful selection of an appropriate climate model. To rationalize such uncertainties and select suitable models, a multi-criteria ranking technique has been employed. Ranking of RCMs has been done on its capability to simulate hydrologic components, i.e., simulations of the surface runoff by employing Soil Water Assessment Tool (SWAT), exercising Entropy, and PROMETHEE-2 approach. The spatial extent of changes in the hydrologic components is examined over the Ganga river basin, using the top three ranked RCMs, for a period from January 2021-December 2100. For the monsoon months (June-September), the future annual mean surface runoff will decrease substantially (-50% to -10%), while the flows for post-monsoon months (October-December) are projected to increase (10-20%). Extremes are noted to increase during the non-monsoon months, while a substantial decrease in medium events is also highlighted. Snow-melt is projected to increase during the months of November-March (50% to 400%). Major loss of recharge is expected to occur in the central part of the basin. The investigation presents not only a reliable impact assessment but also the valuation of future alterations in individual hydrological components and will furnish the administrators with substantive information, a prerequisite to formulating ameliorative policies.
... According to Molina-Navarro et al. (2018), it requires interdisciplinary approach to understand the factors involved and their interactions, and contributes to water resources impact mitigation. Adequate land use planning is central in such approach (Neupane and Kumar, 2015). ...
Changes in climate and in land use/cover can compromises water resources availability and quality, conditioning the planning and management of these essential resources. The objective of this research was to understand the environmental dynamics of the studied region considering this context and to develop instruments for the best management of water resources, based on Potential Runoff Charts generated from natural and anthropic environment attributes consideration in the years 2001 and 2017. The study area was the Rio Claro Watershed (RCW), which covers 251.91km² and is located in the northwest region of São Paulo State, Brazil. Analytic Hierarchy Process (AHP) was used to define weights of the environmental attributes: steepness; total annual rainfall; land use/cover; soil; landforms; and aquifer units. The charts present the surface runoff in five classes (Very Low, Low, Medium, High, and Very High). The results showed significant changes in the period, due to climate changes, and, secondly, due to land use/cover changes. While in 2001 the Low and Medium Potential classes (59.3%) predominated, in 2017 the Medium and Very Low Potential classes (56.5% total) were the most common. High and Very High Potential classes showed small variations in the two years. Results derivate especially from lower rainfall in 2017 compared to 2001, showing that climate changes does not always mean an increase in rainfall on a regional scale and that water resources management instruments should consider such situations. The proposed measures aim to favor infiltration, reduce erosive processes, and favoring aquifers recharge.
... Most of the above-mentioned directives have recently resulted in the generation of many innovative methods and bioecologically/environmentally based models (without the use of data from national monitoring programmes) for the quality assessment of water resources in the EU [20]. Furthermore, the synthetisation of input variables (e.g., physicochemical and hydrological properties of river basins, agroecological conditions, land use, fertiliser application, crop/livestock production) by means of Geographical Information Systems (GIS) has been successful in predicting nitrogen emissions from different (non)point pollution sources (agriculture, urban areas, wastewater treatment plants, industrial discharges) at the catchment-scale level by using: INCA [21], SWAT [22], MONERIS [23], Generalised Linear and Boosted Regression Trees [24], Linear Mixed Effects [25], and other multi-criterial models or approaches [26,27]. In general, methods based on (i) topology are recommended to help in pre-processing stations or sub-basins, (ii) geostatistics is recommended for specific monitoring with high spatial correlation, (iii) hydrology combined with optimization can facilitate statistical analysis to propose new candidate stations, while (iv) multivariate statistical approaches are most commonly used in designing water quality monitoring, but they fail when a new network is proposed for catchment characteristics [28]. ...
Background
The Nitrates Directive (ND) is an EU anti-pollution legislative that, for almost 30 years, has controlled and protected hydro-resources against excessive levels of nitrates originating from agroecosystems, striving to prevent the further exacerbation of the nitrates in aquatic environments. ND sets several principal goals that member states must accomplish, such as performing spatiotemporal nitrate analyses in ground/surface water networks to achieve national water quality monitoring programme.
Results
In this study, using the novel LUMNAqSoP approach, the prioritisation of 151 candidate groundwater stations for ND monitoring in Croatia was performed. The LUMNAqSoP integratively evaluates: (i) the most dominant loads from the agroecosystem (land use and management, net nitrogen application) and (ii) environmental (aquifer and soil) vulnerabilities and sensitivities of groundwater resources to nitrate pollution. By comparing stations which scored the most agro-environmental loads vs. the data from water stations containing elevated mean nitrate concentrations (from existing monitoring programmes) a very good agreement was confirmed. Moreover, deviations close to large urban zones were detected, suggesting that elevated nitrates in groundwaters in those areas likely originated from municipal/industrial rather than agricultural sources; however, further studies are needed for elucidation.
Conclusions
The presented approach can serve as a useful tool to policy makers and regulators for: (i) more efficient and reliable establishment of water monitoring programme pursuant to ND, as well as (ii) better management and shaping (designating/derogating) of nitrate-vulnerable zones, especially in diverse environmental conditions and dynamic agroecosystems as have been confirmed in recent decades across the EU member states.
... In the Lobo Stream Hydrological Basin, its cultivation has grown by some 10% in 30 years (Anjinho et al. 2019), encompassing 23.66 km 2 or 10.70% of the basin. Thus, the study demonstrates the need for greater attention to the development of anthropic activities in the basin, in particular, agricultural activities, the principal source of its nutrients, as crop fertilization increases nitrogen load in watercourses through surface runoff, while phosphorus load reaches watercourses primarily through soil erosion and sediment transport (Molina-Navarro et al. 2018). Accordingly, it is necessary to adopt management practices that favor soil and water conservation and reduce erosion and leaching of soil nutrients. ...
A significant contributor to water pollution is increased nutrient concentration that results in eutrophication. Modeling approaches are crucial to understanding the dynamics of nutrients in river basins. This study integrates empirical models into Geographic Information Systems to quantify total nitrogen and phosphorus (TN and TP) load and concentration in watercourses of Brazil’s Lobo Stream Hydrographic Basin (LSHB). Land use, topographic, demographic, and hydrological data were used to simulate the load and concentration of nutrients generated by point and nonpoint pollution sources. The results indicate that the simulated TN and TP load is primarily generated by nonpoint sources, 81% and 76%, respectively. The Itaqueri River subbasin is the most critical, yielding more than half of the basin’s TN and TP load. About 90% of annual LSHB point pollution load is generated in the Itaqueri River subbasin, principally from the Água Branca Stream. The linear regression between simulated and observed concentration indicates significant relationships (TN, r² = 0.73 (p < 0.05), TP, r² = 0.78 (p < 0.05)). The method used was able to simulate TN and TP concentration in watercourses, but was inconsistent for point pollution, indicating it represents the dynamics of nutrients in rural basins more effectively than in urban ones. The study shows that its methodology, despite limitations, enables scientists and managers to understand and predict spatial distribution of nutrient concentration in LSHB watercourses.
... Many studies have shown that the effects of climate change on streamflow are different in different regions and that spatial heterogeneity exists (Dinpashoh et al., 2019;Molina-Navarro et al., 2018). According to Eqs. (5) and (6), ∂Q/∂P and ∂Q/∂E 0 change with the aridity index (ϕ = E 0 /P) and ω within the theoretical range, which are shown in Figs. 3 and 4. Fig. 3 shows that ∂Q/∂P has a decreasing trend from 1.0 and is getting closer to 0.0 with ϕ increases. ...
In the past 50 years, the decrease of river runoff in China has attracted wide attention from government decision-making departments and the public. The Baiyangdian catchment is one of the regions with the most serious water shortage and the most prominent human-water conflicts, and attribution analysis of the runoff change is of considerable interest at a range of spatial scales. The Budyko framework has been widely used to attribute changes in streamflow to the effects of climate and catchment changes. In this study, we used the elasticity method based on the Budyko framework to examine the sensitivity of streamflow to climate and catchment variables, which indicated that a 1-mm decrease in precipitation would induce a 0.3546-mm decrease in streamflow, a 1-mm decrease in potential evapotranspiration would induce a 0.1045-mm increase in streamflow, and an increase of 1 in the catchment characteristic coefficient would induce a 79.6711-mm decrease in streamflow. The absolute sensitivities of streamflow to climate variables decreased with increases in the aridity index, which indicates that the streamflow was more sensitive to climate change in wet regions. Among the total changes in streamflow (−43.41 mm), the effect of climate change was +3.86 mm (accounting for 7.55%), and the effect of the catchment characteristic changes is −45.99 mm (accounting for 89.95%) based on the sensitivity analyses. The results indicate that streamflow changes in the Baiyangdian catchment are mainly caused by catchment changes.
The Environmental Management Cycle for Chemicals and Climate Change (EMC ⁴ ) is a suggested conceptual framework for integrating climate change aspects into chemical risk management. The interaction of climate change and chemical risk brings together complex systems that are imperfectly understood by science. Making management decisions in this context is therefore difficult and often exacerbated by a lack of data. The consequences of poor decision making can be significant for both environmental and human health. This paper reflects on the ways in which existing chemical management systems consider climate change and proposes the EMC ⁴ conceptual framework that is a tool for decision makers operating at different spatial scales. Also presented are key questions raised by the tool to help the decision maker identify chemical risks from climate change, management options and, importantly, the different types of actors that are instrumental in managing that risk. Case studies showing decision making at different spatial scales are also presented highlighting the conceptual framework's applicability to multiple scales. The United Nations Environment Programme's development of an intergovernmental Science Policy Panel on Chemicals and Waste has presented an opportunity to promote and generate research highlighting the impacts of chemicals and climate change interlinkages.
Best management practices (BMPs) have wide application in non-point source (NPS) pollution abatement in agricultural watersheds. Multivariate analysis of BMPs reduction effects taking their randomness and correlations into account is significant to spatial optimization of BMPs configuration. However, quantifying the correlations among high-dimensional random variables of BMPs effects is challenging and remains unexplored thoroughly. This study coupled the SWAT with the Vine Copula model to conduct multivariate analysis of BMPs reduction effects considering their randomness caused by hydro-meteorological variability along with correlations among different indicators (ammonium nitrogen, NH3-N; and total phosphorus, TP) and BMPs. The coupled model was applied to evaluate the multi-indicator effect of individual BMP and combined effect of various BMPs in the upper Boyang River basin, China. Results showed that bivariate copulas and three-dimensional vine copulas can efficaciously describe the dependence of BMPs effects. Simulation results indicate 43–100% probabilities of 45% NH3-N loads reduction, while 0–79% probabilities of 45% TP loads reduction for combined BMPs scenarios. Besides, the joint probabilities of different indicators in combined BMPs scenarios are generally lower than separate probabilities with 0–21% decrease, which is similar to individual BMP. Generally, joint probabilities using copulas can provide more accurate and factual knowledge of the risk and dependability of implementation of BMPs than univariate variables. The proposed model can conduct multivariate analysis of BMPs reduction effects and has great prospect in the future risk-based decision-making of NPS pollution management.
The study of groundwater–surface water interaction has attracted growing interest among researchers in recent years due to its wide range of implications from the perspectives of water management, ecology and contamination. Many of the studies shed light on conditions on a local scale only, without exploring a regional angle. To provide a broad and historical overview of groundwater–surface water interaction, a review of research carried out in Denmark was undertaken due to the high density of studies conducted in the country. The extent to which this topic has been investigated is related to Denmark's physiography and climate, the presence of numerous streams and lakes combined with shallow groundwater, and historical, funding, and administrative decisions. Study topics comprise groundwater detection techniques, numerical modeling, and contaminant issues including nutrients, ranging from point studies all the way to studies at national scale. The increase in studies in recent decades corresponds with the need to maintain the good status of groundwater‐dependent ecosystems and protect groundwater resources. This review of three decades of research revealed that problems such as the difference in scales between numerical models and field observations, interdisciplinary research integrating hydrological and biological methods, and the effect of local processes in regional systems remain persistent challenges. Technical progress in the use of unmanned aerial vehicles, distributed temperature sensing, and new cost‐effective methods for detecting groundwater discharge as well as the increasing computing capacity of numerical models emerge as opportunities for dealing with complex natural systems that are subject to modifications in future triggered by climate change.
This article is categorized under: Science of Water > Hydrological Processes
Science of Water > Water and Environmental Change
Water and Life > Nature of Freshwater Ecosystems
Abstract Storylines are introduced in climate science to provide unity of discourse, integrate the physical and socioeconomic components of phenomena, and make climate evolution more tangible. The use of this concept by multiple scholar communities and the novelty of some of its applications renders the concept ambiguous nonetheless, because the term hides behind a wide range of purposes, understandings, and methodologies. This semi‐systematic literature review identifies three approaches that use storylines as a keystone concept: scenarios—familiar for their use in IPCC reports—discourse‐analytical approaches, and physical climate storylines. After screening peer‐reviewed articles that mention climate and storylines, 270 articles are selected, with 158, 55, and 57 in each category. The results indicate that each scholarly community works with a finite and different set of methods and diverging understandings. Moreover, these approaches have received criticism in their assembly of storylines: either for lacking explicitness or for the homogeneity of expertise involved. This article proposes that cross‐pollination among the approaches can improve the usefulness and usability of climate‐related storylines. Among good practices are the involvement of a broader range of scientific disciplines and expertise, use of mixed‐methods, assessment of storylines against a wider set of quality criteria, and targeted stakeholder participation in key stages of the process.
Currently, climate change is considered as an important factor affecting nutrient loads introduced through riverine systems into the Baltic Sea. Although the prospect of a large increase in pollution has long seemed very real, it still does not translate into planning of effective remedial actions. One of the factors limiting the development of such activities is the scale of simulations, focusing generally on catchment outlet profiles. To fill this gap and enable a step forward in understanding responses towards future predictions in a higher resolution scale (subcatchment), we assessed nutrient load contribution using calculation profiles localised along a main watercourse and its tributaries. To track spatial and seasonal changes of total nitrogen and phosphorus under short-and long-term (RCP4.5 and RCP8.5) climate change scenarios we used the digital platform Macromodel DNS/SWAT. Having at our disposal a catchment model with a good performance we could follow not only total load changes in particular subcatchments, but also track localisation of the pollution sources and their direct impact on load estimations. Our results showed an increase of the loads, especially from the agricultural landuse type, up to 34% for TN and 85% for TP in the most extreme scenario. Moreover, forest areas have been noted as highly reactive to the climate changes, and through their localisation able to distinctly alter nutrient outflow. Finally, the contribution of urban areas should be further investigated since the dynamics of nitrogen and phosphorus release from impervious surfaces is noticeably different here than from the other diffuse sources.
Climates, Land use/land cover (LULC) and vegetation growing dynamics have been regarded as the main factors affecting terrestrial hydrological process. However, the mechanisms underlying their integrated effects on terrestrial runoff and nutrient dynamics are not understood well. Here, we constructed a framework to disentangle and quantify the independent and coupled contributions of climate, LULC and vegetation leaf area index (LAI) changes to watershed runoff and nutrient yields changes. Long series of changing meteorological, LULC and LAI data between 1990 and 2020 were integrated into a factor-controlled simulation protocol in a distributed hydrological model, to quantify their comprehensive contributions (individual contribution of single factor change and coupling contribution of multiple factor synchronous changes) to runoff and nutrient changes. The results showed that changes of runoff and nutrient yields are more induced by climate change, rather than LULC and LAI transformations. Increase in annual precipitation significantly elevated runoff and nutrient yields. TP yield was more sensitive to climate change than runoff and TN yields. LULC transformation and climate change have synergistic effects on runoff and nutrient yields. Shift of vegetation areas to construction lands will amplify the effect of climate change on runoff and nutrient yields. Single LAI change has weak effect on runoff and nutrient yields, but it can significantly alter the hydrological effects derived from climate change and the synergistic effects between climate change and LULC transformation. This study considered the coupling and potential synergistic effects among climate change, LULC conversion and LAI variation, which elucidated the comprehensive effects of changing environment on runoff and nutrients evolutions in a more systematic and integrated perspective.
The Qinghai-Tibet Plateau (QTP) is the source for many of the most important rivers in Asia. It is also an essential ecological barrier in China and has the characteristic of regional water conservation. Given this importance, we analyzed the spatiotemporal distribution patterns and trends of 10 water quality parameters. These measurements were taken monthly from 67 monitoring stations in the northeastern QTP from 2015 to 2019. To evaluate water quality trends, major factors influencing water quality, and water quality risks, we used a series of analytical approaches including Mann-Kendall test, Boruta algorithm, and interval fuzzy number-based set-pair analysis (IFN-SPA). The results revealed that almost all water monitoring stations in the northeastern QTP were alkaline. From 2015 to 2019, the water temperature and dissolved oxygen of most monitoring stations were significantly reduced. Chemical oxygen demand, permanganate index, five-day biochemical oxygen demand, total phosphorus, and fluoride all showed a downward trend across this same time frame. The annual average total nitrogen (TN) concentration fluctuation did not significantly decrease across the measured time frame. Water quality index (WQI-DET) indicated bad or poor water quality in the study area; however, water quality index without TN (WQI-DET′) reversed the water quality value. The difference between the two indexes suggested that TN was a significant parameter affecting river water quality in the northeastern QTP. Both Spearman correlation and Boruta algorithm show that elevation, urban land, cropland, temperature, and precipitation influence the overall water quality status in the northeastern QTP. The results showed that between 2015 and 2019, most rivers monitored had a relatively low risk of degradation in water quality. This study provides a new perspective on river water quality management, pollutant control, and risk assessment in an area like the QTP that has sensitive and fragile ecology.
Climate change has significant implications for irrigated agriculture and global food security. Understanding how altered precipitation patterns and magnitudes, coupled with rising growing season temperatures, affect irrigation demand and crop production is a prerequisite for formulating effective water resources management strategies. This study evaluated the effects of near-term climate change (centered on 2035) on irrigation demand, green water scarcity, and row crop yields in a major agricultural watershed in southern New Jersey, USA. Downscaled precipitation and temperature from six General Circulation Models (GCMs) for two representative concentration pathways (RCP-4.5 and 8.5) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) were used to drive the Soil and Water Assessment Tool hydrological model.
Temperature and precipitation increases resulted in greater surface runoff, lateral flow, groundwater recharge, and total streamflow. Seasonal ET for corn is projected to alter between −3.0 % to 0.5 %, with irrigation demand between −17 % to −1 %, and yield ranges between −4 % to +9 % depending on the GCMs in the RCP-4.5 scenario, with similar patterns projected by RCP-8.5 scenario. For soybean, the simulation also indicates a declining trend of ET and irrigation demand while increasing yield. Increasing yield for both crops is attributed to changes in agronomic management practices combined with genetically improved cultivars and higher soil fertility due to CO2 fertilization. Green water scarcity analysis under future climate change for corn and soybean display a decreased soil moisture stress due to increased water use efficiency resulting from reduced stomatal conductance under elevated CO2 concentration.
The water quality of Le 'an River Watershed (LRW) is crucial to the water environmental safety of Poyang Lake, especially the concentration of nitrogen and phosphorus. The effect of climate and land use change on watershed water quality has always been under the attention of local managers. More importantly, the lack of detailed studies on climate and land use impact on river water quality has prevented sustainable water security management in the LRW. Therefore, this study aimed to quantify the weight of climate and land use on nutrient loss in the LRW, respectively. We divided the historical period (1990–2020) into six scenarios and a baseline scenario. TN and TP losses in the watershed were simulated using Soil and Water Assessment Tool (SWAT), and the weight of climate and land use were quantified in overall, by period, and by region. The results showed that the weight of climate was greatly higher than land use with values around 90%. However, the weight of land use had a positive cumulative effect in a certain period, and its influence could not be neglected. The climate in all scenarios led to a reduction in nutrient loss, while land use was found to slightly increase the nutrient loss yield. In addition to, unique regional topographic features, urbanization rates, and climatic conditions could cause spatial heterogeneity in the climatic and land use weights.
Detailed information on species temperature preferences are needed to measure the effects of global warming on species and communities in European rivers. However, information currently available in the literature on taxon-specific temperature preferences or temperature tolerances is very heterogeneous and therefore not well suited for forecasting purposes. To close this gap, we derived so-called 'central temperature tendencies' (CTTt values) for benthic invertebrate species. For this end, 547 species and temperature data from regional monitoring programmes in Germany collected at 4,249 sites were analysed. Due to the vulnerability of species to high temperatures, CTTt values were calculated for mean summer temperatures, following a robust approach of calculating a weighted average based on temperature classes. Derived CTTt values correspond well to species temperature preferences as reported in literature as long as the latter were homogeneous in terms of how they were derived and which temperature reference was at focus. Based on taxon-specific CTTt values, a community value, CTTCom, was calculated for each benthic invertebrate sample. CTTCom values were validated by correlation with mean summer water temperatures. As the slope a of the linear regression model between CTTCom values and measured summer temperatures was comparatively low (a = 0.49), a correction function was derived in order to optimise the relation between both. This was crucial, because it is assumed that although CTTt was derived solely from taxa abundances within summer temperature classes, CTTCom not only reflects the effect of (summer) water temperature itself, but also corresponds to a temperature equivalent value, which describes the overall quality of all respiration-relevant aquatic summer habitat conditions that determine the metabolism of respective benthic invertebrates. By comparing this equivalent value with water temperatures measured in the year previous of sampling, statements can be made about the influence of flow conditions and other factors determining oxygen availability.
Thus, CTTCom reflects the mean aerobic scope of the overall benthic invertebrate fauna: the better the respiration conditions for rheophilic species with high oxygen demand, the larger the aerobic scope and the lower CTTCom.
The approach taken in our study is promising and provides a tool to track and even project past, present, and future impacts of global warming on benthic invertebrates in rivers based on measured values of respiratory relevant environmental variables. We encourage all stakeholders in the field of freshwater ecology to test this tool, which is already in use in river management practice in Germany and is known under the long or short terms KLIWA-IndexMZB or KIMZB.
Stormflow runoff is an important non-point source of pollution in drinking water reservoirs. Rationally managed flood discharge processes at estuaries can reduce the high concentration of pollutants carried by runoff, and thus their impacts on water plant operations. In this study, the physical and chemical water quality parameters upstream from a dam were measured for a flood discharge process in the Jinpen Reservoir of Northwest China. The results showed that the time needed for the flood to reach the reservoir was ∼9 h after flooding began, and this lag effect meant that water in the metalimnion and hypolimnion were vented in advance. Consequently, the undercurrent intruded into the hypolimnion. The water temperature increased by 1.83 °C, and the Schmidt stability index decreased from 3291.37 J m⁻² to 2496.32 J m⁻². Flood discharge can effectively reduce the volume of pollutants; however, it cannot completely prevent the deterioration of water quality in the main reservoir. The turbidity of the reservoir still exceeded 300 NTU after the flood discharge. When the outflow discharge decreased, the critical height of aspiration also decreased, and dissolved pollutants could neither be vented nor precipitated quickly, not allowing their concentration within the reservoir to decrease further. A three-dimensional hydrodynamic model was successfully used to simulate flood processes and determine an optimal flood discharge plan. We found that the elevations of the outlet and undercurrent layer are essential to determine the efficiency of flood discharge, while appropriate timing and outflow discharge volumes may further enhance the results. Therefore, using a hydrodynamic model to predict the position of an undercurrent layer, and opening spillways near the elevation of the undercurrent layer can improve the efficacy of flood discharge. Our findings provide novel insights that may be used to improve the operation and management of source water reservoirs.
Increasing nutrient loads from land use and land cover (LULC) change degrade water quality through eutrophication of aquatic ecosystems globally. The Vaal River Catchment in South Africa is an agriculturally and economically important area where eutrophication has been a problem for decades. Effective mitigation strategies of eutrophication in this region require an understanding of the relationship between LULC change and water quality. This study assessed the long-term impacts of LULC changes on nitrate (NO3-N) and orthophosphate (PO4-P) pollution in the lower Vaal River Catchment between 1980 and 2018. Multi-year LULC was mapped from Landsat imagery and changes were determined. Long-term trends in NO3-N and PO4-P loads and concentrations in river water samples were analysed, while multi-year LULC data were ingested into the Soil and Water Assessment Tool (SWAT) to simulate the impacts of LULC changes in NO3-N and PO4-P loads. Main LULC changes included an increase in the irrigated area by 262% and in built-up area by 33%. This occurred at the expense of cultivated dryland fields and rangelands. In situ data analysis showed that at the catchment inlet, PO4-P concentration and loads significantly increased, while NO3-N concentration and loads decreased between 1980 and 2018. At the catchment outlet, only PO4-P loads increased, while NO3-N loads and concentrations remained the same. SWAT simulations at the Hydrologic Response Unit scale showed that irrigated land was the largest contributor to NO3-N leaching per ha. Aggregation of nutrient loads by LULC type showed increased nutrient loads from irrigated and built-up areas over time, while loads from dryland areas decreased. At catchment scale, dryland remained an important contributor of the annual nutrient loads total because of its large area. In future, research efforts should focus on crop management practices to reduce nutrient loads.
This book collects recent and original contributions in the field of climate and underlying human influences on renewable groundwater resources and/or stream–aquifer interactions. The readers can find the contributions both interesting and inspiring when exploring the field of impacts of climate (past, current, and future) on natural, premeditated, and unpremeditated aquifer recharge sources determining the renewable fraction of the groundwater resource. The findings and methods presented in these original contributions will be of interest in some associated problematics concerning stream–aquifer interactions in drylands and mountainous areas, the resilience of groundwater-dependent ecosystems to future climate change and human action, land-subsidence problems in the future, and the influence of climate change on groundwater resources availability and its implication for sustainable groundwater management policies ahead. The Editors envision that these contributions would also be of interest to researchers and practitioners and help identify further research routes.
Francisco Javier Alcalá
David Pulido-Velázquez
Luis Ribeiro
Editors
The burgeoning population and uncontrolled extraction to satisfy the need of the growing population, has induced major changes in the land use and land cover which in turn has imbibed global warming and corresponding changes in the regular pattern of climate. As a result, the flow amount and frequency in a river also get affected and often fails to maintain the equilibrium required to sustain a healthy watershed. The estimation of stream-flow was a popular topic for a long span of time especially for the ungauged basins. The linearity and inability to represent the randomness of stream flow estimation by the empirical models yields the necessity of modern and advanced models which can respond to the uncertainty involved in prediction of flow amount or frequency. However, due to the data dependency and lack of data for the ungauged basins, different models were proposed to estimate stream-flow from lumped data set which ultimately generates an erroneous model. That is why, the present investigation aims to develop a model which tries to retrieve required data from changes in the land use and covers. As land features and uses can be captured remotely by satellites such a model where stream-flow is estimated as a function of changes in different land use and covers can reduce the need of primary or on-site data along with historical data sets for prediction of flow pattern. The present investigation aims to develop a model for estimation of flow amount which have the input variable depending on the change in land use features by the help of neural networks and multi criteria decision making models. An accuracy level of above 95% indicates the advancement of the model and its wide circulation for providing sustainable benefits to the local inhabitants.
Study region: The Qilian Mountain, northwestern China.
Study focus: Land degradation is a global eco-environmental issue. To minimize soil erosion and land degradation, China has implemented several ecological engineering such as “Grain for Green” program (GFG) since 1999. Relationship between vegetation and water budgets in catchments has been widely studied, however very few studies addressed the effects of eco-environmental restoration on water balance in mountain areas, especially with a focus on soil moisture content. Therefore SWAT model was used to quantify the effects of ecological engineering actions (taken place in 2005) on water balance in Qilian Mountain.
New hydrological insights for the region: After the ecological engineering, water yield and soil water content experienced an increment of 32%, and 46%. The opposite trend was monitored in runoff and evapotranspiration, which decreased by 48% and 4%, respectively. Therefore ecosystem restoration have increased soil water retention capacity, a greater proportion of precipitation reaching the catchment is absorbed by the soil rather than flowing out of the region as runoff. Therefore trade-offs between environmental sustainability and water resources security should be carefully addressed in arid region that experienced severe water shortages.
Various ongoing researches are there on topics like which model will give more compatible results with that of observed discharges. It was argued that even complex modeling does not provide better results. Climate change and soil heterogeneity has got an important role in finding out surface runoff. In this paper, we are going to discuss briefly about variable infiltration capacity model (VIC), TOPMODEL, HBV, MIKESHE and soil and water assessment tool (SWAT) model. VIC performs well in moist areas and can be efficiently used in the water management for agricultural purposes. Requirement of large data and physical parameters makes the use of MIKE SHE model limited to smaller catchments. Only a little direct calibration is required for SWAT model to obtain good hydrologic predictions. HBV model gives satisfactory results and TOPMODEL can be used in catchments with shallow soil and moderate topography.
Some agricultural areas lose considerably more than the average amounts of nutrients to waterways (high risk areas, HRAs) and others considerably less than the average (low risk areas, LRAs). These areas are of great interest when river catchment managers seek to both reduce nutrient loads to lakes and marine areas and to allow intensive agriculture. If HRAs were farmed with decreased inputs of fertilizers the environmental benefit would be larger here than from any other areas, and if LRAs were farmed with increased fertilizer use it could be done here causing less environmental damage than at any other areas. If both these changes were applied within the same catchment they might counter balance each other and give the possibility of intensified farming without causing environmental deterioration. We used the semi-distributed SWAT model to identify both HRAs and LRAs in an intensely farmed lowland catchment in Denmark. These areas are classified as the 10% of the agricultural area leaching, respectively, the most and the least nitrogen. Two scenarios were run for HRAs (reduced fertilizer input by 20%) and LRAs (increased fertilizer input by 20%) separately and two were run where both HRAs and LRAs were included. The scenario results showed that the HRA scenario yielded a decrease (3.3%) in nitrate river load at the catchment scale and that the LRA scenario yielded only a small increase (0.9%). The combined scenarios showed an overall decrease in river nitrate load (2.2%).
The pronounced increase in the cycling and deposition of biologically reactive dissolved inorganic nitrogen (DIN) over large areas globally not only cause increased concentrations of DIN in surface waters, but it will also affect nutrient ratios in rivers, lakes and coastal areas. This review addresses the flux and fate of DIN, focusing NO3 in lakes of boreal and alpine catchments. Not only DIN-deposition, but also catchment properties strongly affect the concentrations of NO3 in lakes, as well as NO3:total P (TP) ratios. This ratio displays an extreme variability, and does also serve as an indicator of shift between N and P-limitation of aquatic autotrophs. A high share of forests and bogs in the catchment generally decreases NO3:total P ratios, while alpine and subalpine catchments with sparse vegetation cover may have high NO3:total P ratios, especially in regions with high DIN-deposition. Several empirical and experimental studies indicate a shift from an initial N to P-limitation, but for N-limited lakes, an increased growth of phytoplankton, periphytes and macrophytes may be accredited to elevated inputs of DIN. An intensified P-limitation may also be a consequence of elevated DIN-deposition. This P-limitation may again yield higher C:P-ratios in autotrophs with negative impacts on grazers and higher trophic levels.
There is an ongoing discussion whether floods occur more frequently today than in the past, and whether they will increase in number and magnitude in the future. To explore this issue in Sweden, we merged observed time series for the past century from 69 gauging sites throughout the country (450 000 km(2)) with high-resolution dynamic model projections of the upcoming century. The results show that the changes in annual maximum daily flows in Sweden oscillate between dry and wet periods but exhibit no significant trend over the past 100 years. Temperature was found to be the strongest climate driver of changes in river high flows, which are related primarily to snowmelt in Sweden. Annual daily high flows may decrease by on average -1% per decade in the future, mainly due to lower peaks from snowmelt in the spring (-2% per decade) as a result of higher temperatures and a shorter snow season. In contrast, autumn flows may increase by + 3% per decade due to more intense rainfall. This indicates a shift in floodgenerating processes in the future, with greater influence of rain-fed floods. Changes in climate may have a more significant impact on some specific rivers than on the average for the whole country. Our results suggest that the temporal pattern in future daily high flow in some catchments will shift in time, with spring floods in the northern-central part of Sweden occurring about 1 month earlier than today. High flows in the southern part of the country may become more frequent. Moreover, the current boundary between snow-driven floods in northern-central Sweden and rain-driven floods in the south may move toward higher latitudes due to less snow accumulation in the south and at low altitudes. The findings also indicate a tendency in observations toward the modeled projections for timing of daily high flows over the last 25 years. Uncertainties related to both the observed data and the complex model chain of climate impact assessments in hydrology are discussed.
This chapter reviews the scientific evidence published since the IPCC Fourth Assessment Report (AR4) on observed and projected impacts of anthropogenic climate change in Europe and adaptation responses. The geographical scope of this chapter is the same as in AR4 with the inclusion of Turkey. Thus, the European region includes all countries from Iceland in the west to the Russian Federation (west of the Urals) and the Caspian Sea in the east, and from the northern shores of the Mediterranean and Black Seas and the Caucasus in the south to the Arctic Ocean in the north. Impacts above the Arctic Circle are addressed in Chapter 28 and impacts in the Baltic and Mediterranean Seas in Chapter 30. Impacts in Malta, Cyprus, and other island states in Europe are discussed in Chapter 29. The European region has been divided into five sub-regions (see Figure 23-1): Atlantic, Alpine, Southern, Northern, and Continental. The sub-regions are derived by aggregating the climate zones developed by Metzger et al. (2005) and therefore represent geographical and ecological zones rather than political boundaries. The scientific evidence has been evaluated to compare impacts across (rather than within) sub-regions, although this was not always possible depending on the scientific information available. 23.1.1. Scope and Route Map of Chapter, The chapter is structured around key policy areas. Sections 23.3 to 23.6 summarize the latest scientific evidence on sensitivity climate, observed impacts and attribution, projected impacts, and adaptation options, with respect to four main categories of impacts: • Production systems and physical infrastructure • Agriculture, fisheries, forestry, and bioenergy production • Health protection and social welfare • Protection of environmental quality and biological conservation The benefit of assessing evidence in a regional chapter is that impacts across sectors can be described, and interactions between impacts can be identified. Further, the cross-sectoral decision making required to address climate change can be reviewed. The chapter also includes sections that were not in AR4.
1930 Climate change may have profound eff ects on phosphorus (P) transport in streams and on lake eutrophication. Phosphorus loading from land to streams is expected to increase in northern temperate coastal regions due to higher winter rainfall and to a decline in warm temperate and arid climates. Model results suggest a 3.3 to 16.5% increase within the next 100 yr in the P loading of Danish streams depending on soil type and region. In lakes, higher eutrophication can be expected, reinforced by temperature-mediated higher P release from the sediment. Furthermore, a shift in fi sh community structure toward small and abundant plankti-benthivorous fi sh enhances predator control of zooplankton, resulting in higher phytoplankton biomass. Data from Danish lakes indicate increased chlorophyll a and phytoplankton biomass, higher dominance of dinophytes and cyanobacteria (most notably of nitrogen fi xing forms), but lower abundance of diatoms and chrysophytes, reduced size of copepods and cladocerans, and a tendency to reduced zooplankton biomass and zooplankton:phytoplankton biomass ratio when lakes warm. Higher P concentrations are also seen in warm arid lakes despite reduced external loading due to increased evapotranspiration and reduced infl ow. Th erefore, the critical loading for good ecological state in lakes has to be lowered in a future warmer climate. Th is calls for adaptation measures, which in the northern temperate zone should include improved P cycling in agriculture, reduced loading from point sources, and (re)-establishment of wetlands and riparian buff er zones. In the arid Southern Europe, restrictions on human use of water are also needed, not least on irrigation. O n average, global surface temperatures have increased by about 0.74°C over the past 100 yr (Trenberth et al., 2007), with the majority of the increase (0.55°C) occurring over the past 30 yr. We may expect marked changes to occur in the global climate during this century (IPCC, 2007). Increasingly reliable regional climate projections are available for many regions of the world, but fewer projections are available for many developing countries than for the developed world (Christensen et al., 2007). Th e warming generally increases the spatial variability of precipitation with reduced rainfall in the subtropics and increases at higher latitudes and in parts of the tropics. Th e changes in temperature and rainfall lead to changes in agricul-tural land use and management, including changes in soil cultivation and in the rates and timing of fertilization (Howden et al., 2007). Th ese changes have cascading eff ects on the P cycling, directly and indirectly, that aff ect the aquatic environment. Th e direct eff ects are related to the increased temperatures, increased rainfall intensity, and changes in winter rainfall that are expected to enhance the P loading to freshwaters in the temperate zone (IPCC, 2007) and the Arctic (Arctic Climate Impact Assessment, 2002) and to reduce the loading, but not the concentrations, in streams and freshwater lakes in the Mediterranean region. However, a few quantitative studies are avail-able (Chang, 2004; Andersen et al., 2006). Th e indirect eff ects are related to changes in the choice of crops, crop rotations, use of catch crops, and agricultural practices, including tillage and fertilization. In northern temperate areas, new heat-demanding, warm-season crops (e.g., maize and sunfl ower) will replace many of the present grain cereals and oilseed crops (Olesen and Bindi, 2002). At the same time, changes occur in planting and harvesting times (Olesen, 2005) and in fertilization rates and strategies (Olesen et al., 2007). Crop rotation must be adapted to changes in crop choices, in crop maturing, and in the need to control weeds, pests, and diseases. Th is will aff ect the amount of P released to freshwaters and its seasonal pattern. More-Abbreviation: TP, total phosphorus.
Three coupled climate–carbon cycle models including CESM (Community Earth System Model), CanEsm (the Canadian Centre for Climate Modelling and Analysis Earth System Model) and BCC (Beijing Climate Center Climate System Model) were used to estimate whether changes in land hydrological cycle responded to the interactive effects of CO2-physiological forcing and CO2-radiative forcing. No signs could be indicated that the interactive effects of CO2-physiological forcing and CO2-radiative forcing on the hydrological variables (e.g. precipitation, evapotranspiration and runoff) were detected at global and regional scales. For each model, increases in precipitation, evapotranspiration and runoff (e.g. 0.37, 0.18 and 0.25 mm/year2) were simulated in response to CO2-radiative forcing (experiment M3). Decreases in precipitation and evapotranspiration (about − 0.02 and − 0.09 mm/year2) were captured if the CO2 physiological effect was only accounted for (experiment M2). In this experiment, a reverse sign in runoff (the increase of 0.08 mm/year2) in contrast to M3 is presented. All models simulated the same signs across Eastern Asia in response to the CO2 physiological forcing and radiative forcing: increases in precipitation and evapotranspiration only considering greenhouse effect; reductions in precipitation and evapotranspiration in response to CO2-physiological effect; and enhanced trends in runoff from all experiments. However, there was still a large uncertainty on the magnitude of the effect of transpiration on runoff (decreased transpiration accounting for 8% to 250% of the increased runoff) from the three models. Two models (CanEsm and BCC) attributed most of the increase in runoff to the decrease in transpiration if the CO2-physiological effect was only accounted for, whereas CESM exhibited that the decrease in transpiration could not totally explain the increase in runoff. The attribution of the CO2-physiological forcing to changes in stomatal conductance versus changes in vegetation structure (e.g. increased Leaf Area Index) is an issue to discuss, and among the three models, no agreement appeared.
Global warming impacts the water cycle not only by changing regional precipitation levels and temporal variability, but also by affecting water flows and soil moisture dynamics. In Brandenburg, increasing average annual temperature and decreasing precipitation in summer have already been observed. For this study, past trends and future effects of climate change on soil moisture dynamics in Brandenburg were investigated, considering regional and specific spatial impacts. Special Areas of Conservation (SACs) were focused on in particular. A decreasing trend in soil water content was shown for the past by analyzing simulation results from 1951 to 2003 using the integrated ecohydrological model SWIM (Krysanova et al., 1998). The trend was statistically significant for some areas, but not for the entire region. Simulated soil water content was particularly low in the extremely dry year 2003. Comparisons of simulated trends in soil moisture dynamics with trends in the average annual Palmer Drought Severity Index for the region showed largely congruent patterns, though the modeled soil moisture trends are characterized by a much higher spatial resolution. Regionally downscaled climate change projections representing the range between wetter and drier realizations were used to evaluate future trends of available soil water. A further decrease of average available soil water ranging from -4% to -15% was projected for all climate realizations up to the middle of the 21st century. An average decrease of more than 25mmwas simulated for 34% of the total area in the dry realization. Available soil water contents in SACs were generally higher and trends in soil moisture dynamics were lower mainly due to their favorable edaphic conditions. Stronger absolute and relative changes in the simulated trends for the past and future were shown for SACs within Brandenburg than for the state as a whole, indicating a high level of risk for many wetland areas. Nonetheless, soil water content in SACs is expected to remain higher than average under climate change conditions as well, and SACs therefore have an important buffer function under the projected climate change. They are thus essential for local climate and water regulation and their status as protected areas in Brandenburg should be preserved.
River floodplains and riparian areas are often considered efficient traps for sediment and sediment-associated nutrients such as nitrogen (N) and phosphorus (P). However, few studies have focused on the fate of sediment-bound N and P after deposition on floodplains. In this study, the leaching of N and P from sediment deposited on a Danish-restored floodplain was quantified by placing trapped sediment samples under a rainfall simulator and exposing them to in situ temperatures and precipitation for two months. The nitrate release was 2.72–1600 μg NO3-N.g−1 DW which corresponded to 0.06–6.42% of the total nitrogen contained in the sediment. Total dissolved phosphorus (TDP) release was 0.44–3.17 μg P.g−1 DW, corresponding to 0.021–0.065% of the TP content of the sediment. Our results indicate that N and P release from floodplain sediment subjected to rainfall events is very low, which should be considered when applying floodplain restoration to mitigate the load of N and P to rivers.
The quantification of point and non-point losses of Nitrogen (N) and Phosphorus (P) to surface waters is currently a major
issue for the implementation of Environmental Directives, such as the Water Framework Directive in Europe. However, the drivers
behind nutrient pollution are location specific and are affected by regional hydroclimatic and geomorphological characteristics.
In this study the river basin model SWAT was used in order to improve the process-based understanding of mechanisms behind
nutrient transport from land to water recipients in two European catchments with significantly different meteorological conditions:
the Greek catchment of Ali Efenti, representative of the Mediterranean climate, and the Norwegian catchment of Vansjø-Hobølv,
representative of the cold climate typical in Scandinavia. The models were firstly calibrated according to measured river
flows and nutrient loads, and then four Best Management Practices (BMPs), related to nutrient application and soil management
were applied in order to examine their effectiveness under the different geoclimatic conditions of the two catchments. The
results of the baseline indicated that diffuse agricultural sources were the largest contributor of N losses in both catchments
and of P losses in the Greek catchment, while point sources were significant contributors to P levels in Norwegian rivers.
Nutrient losses to surface waters in Ali Efenti exhibited high seasonal variation, attributed to the extremeness of precipitation
events that is typical in the Mediterranean, as well as to the temporal distribution of sediment losses to waters. On the
other hand, in Scandinavia, the losses of N and P occurred with less deviation throughout the year and independently of the
freezing of soils. The values of the calibrated parameters that mainly governed the hydrological and erosion processes in
the catchments demonstrated the natural driving forces of nutrient losses to waters and their temporal distribution indicating
that these forces are also crucial in determining the appropriate implementation of agricultural management practices in various
geoclimatic regions.
KeywordsBMPs–Diffuse pollution–Geoclimatic conditions–Nitrogen–Phosphorus–Sediments–SWAT
Here, we communicate a point of departure in the development of aquatic ecosystem models, namely a new community-based framework, which supports an enhanced and transparent union between the collective expertise that exists in the communities of traditional ecologists and model developers. Through a literature survey, we document the growing importance of numerical aquatic ecosystem models while also noting the difficulties, up until now, of the aquatic scientific community to make significant advances in these models during the past two decades. Through a common forum for aquatic ecosystem modellers we aim to (i) advance collaboration within the aquatic ecosystem modelling community, (ii) enable increased use of models for research, policy and ecosystem-based management, (iii) facilitate a collective framework using common (standardised) code to ensure that model development is incremental, (iv) increase the transparency of model structure, assumptions and techniques, (v) achieve a greater understanding of aquatic ecosystem functioning, (vi) increase the reliability of predictions by aquatic ecosystem models, (vii) stimulate model inter-comparisons including differing model approaches, and (viii) avoid 're-inventing the wheel', thus accelerating improvements to aquatic ecosystem models. We intend to achieve this as a community that fosters interactions amongst ecologists and model developers. Further, we outline scientific topics recently articulated by the scientific community, which lend themselves well to being addressed by integrative modelling approaches and serve to motivate the progress and implementation of an open source model framework.
Phosphorus loss from bank erosion was studied in the catchment of River Odense, a lowland Danish river basin, with the aim of testing the hypothesis of whether stream banks act as major diffuse phosphorus (P) sources at catchment scale. Furthermore, the study aimed at analyzing the impact of different factors influencing bank erosion and P loss such as stream order, anthropogenic disturbances, width of uncultivated buffer strips, and the vegetation of buffer strips. A random stratified procedure in geographical information system (GIS) was used to select two replicate stream reaches covering different stream orders, channelized vs. naturally meandering channels, width of uncultivated buffer strips (≤ 2 m and ≥ 10 m), and buffer strips with different vegetation types. Thirty-six 100-m stream reaches with 180 bank plots and a total of 3000 erosion pins were established in autumn 2006, and readings were conducted during a 3-yr period (2006-2009). The results show that neither stream size nor stream disturbance measured as channelization of channel or the width of uncultivated buffer strip had any significant ( < 0.05) influence on bank erosion and P losses during each of the 3 yr studied. In buffer strips with natural trees bank erosion was significantly ( < 0.05) lower than in buffer strips dominated by grass and herbs. Gross and net P input from bank erosion amounted to 13.8 to 16.5 and 2.4 to 6.3 t P, respectively, in the River Odense catchment during the three study years. The net P input from bank erosion equaled 17 to 29% of the annual total P export and 21 to 62% of the annual export of P from diffuse sources from the River Odense catchment. Most of the exported total P was found to be bioavailable (71.7%) based on a P speciation of monthly suspended sediment samples collected at the outlet of the river basin. The results found in this study have a great importance for managers working with P mitigation and modeling at catchment scale.
This paper presents a quantitative comparison of plausible climate and land use change impacts on the hydrology of a large-scale agricultural catchment. An integrated, distributed hydrological model was used to simulate changes in the groundwater system and its discharge to rivers and drains for two climate scenarios (2071–2100). Annual groundwater recharge increased significantly (especially the B2 scenario), giving higher groundwater heads and stream discharges and amplifying the seasonal dynamics significantly. Owing to drier summers, irrigation volumes increased by up to 90% compared to current values. Changing the land use from grass to forest had a minor effect on groundwater recharge, whereas CO2 effects on transpiration resulted in a relatively large increase in recharge. This study has shown that climate change has the most substantial effect on the hydrology in this catchment, whereas other factors such as irrigation, CO2 effects on transpiration, and land use changes affect the water balance to a lesser extent.
The most frequently used climate classification map is that of Wladimir Köppen, presented in its latest version 1961 by Rudolf Geiger. A huge number of climate studies and subsequent publications adopted this or a former release of the Köppen-Geiger map. While the climate
classification concept has been widely applied to a broad range of topics in climate and climate change research as well as in physical geography, hydrology, agriculture, biology and educational aspects, a well-documented update of the world climate classification map is still missing. Based
on recent data sets from the Climatic Research Unit (CRU) of the University of East Anglia and the Global Precipitation Climatology Centre (GPCC) at the German Weather Service, we present here a new digital Köppen-Geiger world map on climate classification, valid for the second half of
the 20 century.
German
Die am häufigsten verwendete Klimaklassifikationskarte ist jene von Wladimir Köppen, die in der letzten Auflage von Rudolf Geiger aus dem Jahr 1961 vorliegt. Seither bildeten viele Klimabücher und Fachartikel diese oder eine frühere Ausgabe
der Köppen-Geiger Karte ab. Obwohl das Schema der Klimaklassifikation in vielen Forschungsgebieten wie Klima und Klimaänderung aber auch physikalische Geographie, Hydrologie, Landwirtschaftsforschung, Biologie und Ausbildung zum Einsatz kommt, fehlt bis heute eine gut dokumentierte
Aktualisierung der Köppen-Geiger Klimakarte. Basierend auf neuesten Datensätzen des Climatic Research Unit (CRU) der Universität von East Anglia und des Weltzentrums für Niederschlagsklimatologie (WZN) am Deutschen Wetterdienst präsentieren wir hier eine neue digitale
Köppen-Geiger Weltkarte für die zweite Hälfte des 20. Jahrhunderts.
Watershed models are powerful tools for simulating the effect of watershed processes and management on soil and water resources. However, no comprehensive guidance is available to facilitate model evaluation in terms of the accuracy of simulated data compared to measured flow and constituent values. Thus, the objectives of this research were to: (1) determine recommended model evaluation techniques (statistical and graphical), (2) review reported ranges of values and corresponding performance ratings for the recommended statistics, and (3) establish guidelines for model evaluation based on the review results and project-specific considerations; all of these objectives focus on simulation of streamflow and transport of sediment and nutrients. These objectives were achieved with a thorough review of relevant literature on model application and recommended model evaluation methods. Based on this analysis, we recommend that three quantitative statistics, Nash-Sutcliffe efficiency (NSE), percent bias (PBIAS), and ratio of the root mean square error to the standard deviation of measured data (RSR), in addition to the graphical techniques, be used in model evaluation. The following model evaluation performance ratings were established for each recommended statistic. In general, model simulation can be judged as satisfactory if NSE > 0.50 and RSR < 0.70, and if PBIAS + 25% for streamflow, PBIAS + 55% for sediment, and PBIAS + 70% for N and P. For PBIAS, constituent-specific performance ratings were determined based on uncertainty of measured data. Additional considerations related to model evaluation guidelines are also discussed. These considerations include: single-event simulation, quality and quantity of measured data, model calibration procedure, evaluation time step, and project scope and magnitude. A case study illustrating the application of the model evaluation guidelines is also provided.
The capability of eight nutrient models to predict annual nutrient losses (nitrogen and phosphorus) at catchment scale have been studied in the EUROHARP project. The methodologies involved in these models differ profoundly in their complexity, level of process representation and data requirements. This evaluation is focused on model performance in three core catchments: the Vansjø-Hobøl (Norway), the Ouse (Yorkshire, UK) and the Enza (Italy). These three different model applications have been evaluated by comparing calculated annual nutrient loads (total N or nitrate and total P), based on observed flow and total nitrogen or nitrate and total phosphorus concentrations, and the annual nutrient loads that were simulated by the eight nutrient models. Four statistics have been applied for this purpose: the root mean squared error (RMSE), the mean absolute error (MAE), the mean error (ME), and Nash-Sutcliffe's model efficiency (NS). The results show that all model approaches can predict the calculated annual discharges. Depending on the observed statistics (RMSE, MAE, ME and NS) the scores of the model application differed, therefore no overall 'best model' could be identified. Although the water and nutrient loads from (sub)catchments can be predicted, the modelled pathways of nutrients within agricultural land and the nutrient losses to surface waters from agricultural land vary among the catchments and among those model approaches which are able to make this distinction.
The Soil and Water Assessment Tool (SWAT) model is a continuation of nearly 30 years of modeling efforts conducted by the U.S. Department of Agriculture (USDA), Agricultural Research Service. SWAT has gained international acceptance as a robust interdisciplinary watershed modeling tool, as evidenced by international SWAT conferences, hundreds of SWAT-related papers presented at numerous scientific meetings, and dozens of articles published in peer-reviewed journals. The model has also been adopted as part of the U.S. Environmental Protection Agency's BASINS (Better Assessment Science Integrating Point & Nonpoint Sources) software package and is being used by many U.S. federal and state agencies, including the USDA within the Conservation Effects Assessment Project. At present, over 250 peer-reviewed, published articles have been identified that report SWAT applications, reviews of SWAT components, or other research that includes SWAT. Many of these peer-reviewed articles are summarized here according to relevant application categories such as streamflow calibration and related hydrologic analyses, climate change impacts on hydrology, pollutant load assessments, comparisons with other models, and sensitivity analyses and calibration techniques. Strengths and weaknesses of the model are presented, and recommended research needs for SWAT are provided.
Automatic calibration of complex hydro-ecological models is an increasingly important issue which involves making decisions. One of the most relevant is the choice of the objective function, but its effects have been scarcely studied in complex models. We have used the SWAT model to assess the impact of the objective function for a multi-site (4 stations) and multi-variable (OrgP, OrgN, NO3⁻, PO4³⁻) calibration of the Odense catchment (Denmark). Six calibration schemes were tested, varying the objective function and the nutrient fractions targeted. The best performance metrics (R², NSE, PBIAS) were obtained when using NSE as objective function and targeting N-fractions and P-fractions separately. The scheme was validated in another SWAT set-up in northern Denmark. Although NSE is often questioned, we found it as an adequate objective function when addressing a multi-site and multi-variable calibration. Our findings may serve as guideline for hydro-ecological modellers, being useful to achieve watershed management goals.
Water resources globally are affected by a complex mixture of stressors resulting from a range of drivers, including urban and agricultural land use, hydropower generation and climate change. Understanding how stressors interfere and impact upon ecological status and ecosystem services is essential for developing effective River Basin Management Plans and shaping future environmental policy. This paper details the nature of these problems for Europe's water resources and the need to find solutions at a range of spatial scales. In terms of the latter, we describe the aims and approaches of the EU-funded project MARS (Managing Aquatic ecosystems and water Resources under multiple Stress) and the conceptual and analytical framework that it is adopting to provide this knowledge, understanding and tools needed to address multiple stressors. MARS is operating at three scales: At the water body scale, the mechanistic understanding of stressor interactions and their impact upon water resources, ecological status and ecosystem services will be examined through multi-factorial experiments and the analysis of long time-series. At the river basin scale, modelling and empirical approaches will be adopted to characterise relationships between multiple stressors and ecological responses, functions, services and water resources. The effects of future land use and mitigation scenarios in 16 European river basins will be assessed. At the European scale, large-scale spatial analysis will be carried out to identify the relationships amongst stress intensity, ecological status and service provision, with a special focus on large transboundary rivers, lakes and fish. The project will support managers and policy makers in the practical implementation of the Water Framework Directive (WFD), of related legislation and of the Blueprint to Safeguard Europe's Water Resources by advising the 3rd River Basin Management Planning cycle, the revision of the WFD and by developing new tools for diagnosing and predicting multiple stressors.
