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Abstract

In this paper, a distributed catchment-hydrology model and a physically based lake hydrodynamic model were used to simulate the large-scale and highly dynamic lake catchment system of Poyang Lake, in the middle reach of the Yangtze River basin, China. The simulation of the hydrodynamics of the lake is a significant extension to previous efforts to simulate Poyang Lake's considerable variability in lake extent and flow rates. Further, the combination of the distributed catchment-hydrology model and the lake-hydrodynamic model, applied to a highly dynamic and large-scale system, is a rare attempt to develop a physically based management model of this complexity and scale. Model calibration and validation were undertaken to evaluate the model's performance and to enhance its effectiveness in simulating catchment discharges, lake water levels, lake water surface areas, and lake flow patterns. The results showed a satisfactory agreement with field observations, with Nash-Sutcliffe efficiencies of 0.71-0.84 for catchment discharges, 0.88-0.98 for lake water levels, and 0.80 for lake outflows during the calibration period. The Nash-Sutcliffe efficiency values for the validation period, ranging from 0.62 to 0.97, were largely consistent with the calibration values. Further investigation of the results showed that the modeling approach simulated adequately the lake hydrodynamics in terms of the flow fields within the lake and the seasonal changes in the lake water surface area. The outcomes of this paper will benefit future modeling efforts by providing a tool for predicting the hydrology of Poyang Lake and its catchment under climate variability and land-use changes.

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... The MIKE 21 model is based on a cell-centered finite volume method, with an unstructured mesh to permit accurate representation of complex surface water bodies (DHI, 2014). The model has been widely used to investigate the hydrodynamic characteristics, external drivers, and various assessments of rivers, lakes, wetlands, and coastal oceans (e.g., Martinelli et al., 2010;Li et al., 2014Li et al., , 2020. In addition, the numerical option of wetting and drying in MIKE 21 is most suited to 2D free-surface flows, where inundation area exhibits considerable variations in response to various influencing factors (DHI, 2014;Li et al., 2014). ...
... The model has been widely used to investigate the hydrodynamic characteristics, external drivers, and various assessments of rivers, lakes, wetlands, and coastal oceans (e.g., Martinelli et al., 2010;Li et al., 2014Li et al., , 2020. In addition, the numerical option of wetting and drying in MIKE 21 is most suited to 2D free-surface flows, where inundation area exhibits considerable variations in response to various influencing factors (DHI, 2014;Li et al., 2014). The underlying principles and a mathematical description of MIKE 21 can be found in the reference above. ...
... According to field investigations and published studies (Li et al., 2020), the wetland bottom is an impermeable boundary with spatial resistance specified by variable roughness for tidal creek (Manning number, M = 48-50 m 1/3 /s), vegetation area (M = 32-35 m 1/3 /s), and natural beach (M = 40-45 m 1/3 /s). The Smagorinsky factor of eddy viscosity (C s = 0.28) was derived from previous studies and adopted to perform the hydrodynamic simulation (e.g., DHI, 2014;Li et al., 2014Li et al., , 2020. The minimum time step was restricted to 0.1 s to keep the target Courant-Friedrich-Levy number of 1.0, the maximum time step was set to 900 s. ...
Article
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Estuarine wetlands have experienced a variety of ecological and environmental problems caused by natural and anthropogenic factors. China has proposed a series of measures and made great efforts to control coastal degradation; however, decision makers still urgently need to know which measures to implement and how they will influence the estuarine environment and functions. This study used field observations, a hydrodynamic model, and statistical methods to investigate the effects of potential restoration scenarios on hydrodynamic conditions in the tidal-influenced estuarine wetland system, Liaodong Bay (China). Results reveal that the average total phosphorus, organic carbon, available phosphorus, pH, total nitrogen content, and moisture content in the soil and sediment environment were 0.04 ± 0.003%, 0.84 ± 0.25%, 16.3 ± 4.7 mg/kg, 8.3 ± 0.1, 0.07 ± 0.02%, and 44 ± 2%, respectively, exhibiting an overall trend of degradation. A series of restoration scenarios in regards to hydrodynamic regulation and tidal inputs were used to preserve the ecological value of the estuarine wetland. Model simulations indicate that the significant improvement of hydrodynamic fields (inundation depth and flow velocity) is more likely to occur when the tidal amplitudes reach around 2 m, while relatively weak responses can be observed when the tidal levels are lower than 1 m. Additionally, the construction of floodgates may play a key role in determining the tidal inputs and flowpaths across the wetland. The modifications in micro-topography of the wetland may play a complementary role in enhancing the connectivity condition via increased creek depth of 0.5 m and width up to around 20 m. This work represents a first attempt in exploring hydrodynamic effects of restoration scenarios for a tidal-dominated wetland. An improved understanding of the estuarine system also highlights that the design and implementation of wetland restoration projects should use more comprehensive measures to achieve long-term landscape management, connectivity planning, and ecological sustainability.
... Model calibration and validation procedures have been conducted in many previous studies regarding Poyang lake hydrodynamics and their interactions with the Yangtze River (e.g., Zhang et al. 2014;Zhang and Werner 2015;Li et al. 2014Li et al. , 2017Li et al. , 2018Li et al. , 2019b. The floodplain hydrodynamic model reproduced the hydrological behaviors of the lake-floodplains based on field measurements (i.e., water level, flow velocity, and outflow discharge) and remote sensing data (i.e., water area and inundation) reasonably well. ...
... Although the impact of the complex topography (e.g., the main flow channel, bays, shallow floodplains with narrow rivers) and model's mesh sizes (i.e., 70-1500 m) on generated patterns of hydrodynamics can almost be ignored during high water level periods, slight discrepancies between the simulation and the observation can be found during low lake level seasons (Fig. 4). The simulated trend in major hydrodynamic behaviors is similar to previous modeling investigations of the Poyang Lake-floodplains (e.g., Li et al. 2014;Zhang et al. 2014). Overall, the evaluation presented in Fig. 4 demonstrates the floodplain hydrodynamic model has the capability to represent an annual cycle of rising, high, receding, and low hydrological phases in the Poyang Lake-floodplain system, building confidence in the applicability of the modeling experimental studies. ...
... In the Poyang Lake floodplains, previous work has concluded that lakefloodplain groundwater exhibits significant seasonal exchanges (Li et al. 2018(Li et al. , 2019c. Considering a large number of previous studies about the lake-floodplain hydrodynamic behaviors (e.g., Li et al. 2014Li et al. , 2020bZhang et al. 2015;Yao et al. 2018), further work is needed to combine a field gauging network or groundwater models to provide some new insights regarding the subsurface connectivity across the lake-floodplains and associated linkage with the surface water connectivity. The issue of multiple dimensions on hydrological connectivity is an important, yet challenging, research direction for the future . ...
Article
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Knowledge of hydrological connectivity and its threshold behaviors plays an important role in sustaining and managing floodplains; however, threshold behaviors at a system scale have not received adequate attention. This study used a geostatistical connectivity method in combination with hydrodynamic modeling experiments to provide new insights on the surface hydrological connectivity of water depth thresholds in a flood-pulse-influenced floodplain system (Poyang Lake, China). The results reveal that hydrological connectivity is more sensitive to changes in water depth during dry, rising, and receding water phases than in the flooding phase under different depth thresholds. Geographically, the connectivity patterns show that large water bodies are mainly distributed in the main lake and floodplain river channels; extensive floodplain areas are dynamically connected to the main lake, indicating that the lake's floodplain is a sensitive area of the flood pulse system. From a systemic perspective, the surface water connectivity exhibits abrupt changes under the depth threshold of around 50 cm, demonstrating a rapid system response to the threshold value. In the floodplains of Poyang Lake, surface topography and flood pulse dynamics play a combined role in affecting hydrological connectivity, especially low and intermediate connectivity. The filling-spilling process generally extends from the lower-lying main lake and floodplain rivers to the upper-lying floodplains of the lake. The current work quantifies the influences of depth thresholds on surface hydrological connectivity to pave the way for performing a joint assessment of hydrological connectivity and ecological responses based on developing comprehensive modellings in threshold-affected floodplains. Graphic abstract
... A previously developed 2D depth-averaged hydrodynamic model using the MIKE 21 code was used to investigate the flow characteristics of Poyang Lake (DHI, 2009;Li et al., 2013Li et al., , 2017. The simulated domain of Poyang Lake covers the maximum flood inundation area of 3124 km 2 (Li et al., 2013), which was determined by examining the historic lake surface under high water levels. ...
... A previously developed 2D depth-averaged hydrodynamic model using the MIKE 21 code was used to investigate the flow characteristics of Poyang Lake (DHI, 2009;Li et al., 2013Li et al., , 2017. The simulated domain of Poyang Lake covers the maximum flood inundation area of 3124 km 2 (Li et al., 2013), which was determined by examining the historic lake surface under high water levels. A triangular mesh generated using 2010 data (30 m × 30 m) was adopted to discretize the lake topography, resulting in a total of 20,450 triangular elements. ...
... The size of mesh elements varied from 70 m and 1500 m, respectively, differentiating the lake topography at different scales. The time step was set to 5 s to limit the Courant-Friedrich-Levy number for a stable solution (Li et al., 2013). A drying depth of 0.005 m, a flooding depth of 0.05 m, and a wetting depth of 0.1 m were selected to capture the change of the seasonal drying and flooding of the Poyang Lake floodplains (Yao et al., 2018). ...
... A further motivation for this study is curiosity, as the spatiotemporal changes of Poyang Lake inundation behavior remain to be investigated in detail. The major purpose of this study is to assess the spatial and temporal floodplain hydrological processes in response to the changed river-lake relationship using the floodplain hydrodynamic model proposed by Li et al. [45]. The primary objectives are to examine the effects of the changed river-lake relationship on the temporal and spatial patterns in the hydrological regime in the Poyang Lake floodplains characterized by inundation area, water level, and inundation duration. ...
... In addition, backflow from the Yangtze River to Poyang Lake occurs frequently due to their water level gradient in different flood seasons [21]. Generally, the lake bottom elevation decreases from south to north, with an absolute difference of about 6.5 m [45]. The annual precipitation is around 1654 mm, and the annual potential evapotranspiration is 1049 mm, resulting from a subtropical wet climate [37]. ...
... MIKE 21 is a powerful and popular hydrodynamic modeling system used around the world. The hydrodynamic model MIKE 21 used in this study was recently assembled by Li et al. [45] which was successfully applied to study the hydrological regime of Poyang Lake and the associate causes and potential impacts [5,8,37,40,45,[51][52][53][54]. Based on the previous work, the constructed Poyang Lake hydrodynamic model [45] was the preferred application in our study. ...
Article
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Poyang lake floodplains are hydrologically complex and dynamic systems which exhibit dramatic intra-annual wetting and drying. The flow regime of the Yangtze River was previously known to play an important role in affecting Poyang Lake and its extremely productive floodplains (river–lake relationship). The recent severe declines and recessions in the lake are closely linked to the changed river–lake relationship, resulting in significant hydrological, ecological, and economic problems. This study aims to examine the spatiotemporal heterogeneity of the floodplain hydrodynamic behaviors with respect to impacts of the changed river–lake relationship, characterized by the lake water level, inundation area, and inundation duration based on a floodplain hydrodynamic model of Poyang Lake, and to further quantify the severity of dryness recently endured since 2000. Simulation results show that, in general, the current modified river–lake relationship is more likely to affect the hydrological seasonality of the floodplain system since 2000, relative to the flooding and drying cycles during past decades (1953–2000). The present hydrodynamic behaviors suffered significant change due to the greatest interference from the altered river–lake relationship, particularly for the falling period in October. On average, the floodplain water level and inundation duration decreased by 6 m and 12 days during October, respectively. Additionally, the highest monthly shrinkage rate in floodplain inundation shifted from the period of October–November to September–October, with the mean inundation area decreasing by around 50%, demonstrating an advanced and prolonged dry condition. The spatial responses of the hydrodynamics in the low-slope floodplains are most likely to be affected by the dynamic river–lake relationship, as expected. This study assessed the effects of the altered river–lake relationship on the hydrological regime of the Poyang Lake floodplains in terms of spatiotemporal distributions and changing processes for the periodic inundated behavior, which can support the relevant study of the subsequent ecological effects on the wetlands.
... The hydrological condition in raising period I was highly variable, with a large fluctuation in WL. Furthermore, water flow velocity was relatively high (about 0.80 m s −1 ) (Dou and Jiang, 2003;Li et al., 2014), which was generally consistent to the variation of WL in raising period (Liu et al., 2015). Generally, elevated flow velocity is against to phytoplankton growth (Valdes-Weaver et al., 2006). ...
... Although significant relationship between chl a and WL was also observed in falling period II, WL did not enter the final model, with relative low correlation coefficient (r = 0.32). In falling period II, water flow velocity commonly increased with decreasing WL (Dou and Jiang, 2003;Li et al., 2014), which inhibits phytoplankton growth. This phenomenon may probably result in the positive effect of WL on phytoplankton growth in this period. ...
... The impact of WL on underwater light condition in Lake Poyang was more evident in raising period II. Water flow velocity continually decreased with increasing WL in raising period II (Dou and Jiang, 2003;Li et al., 2014), which reduced sediment particles (especially sand) to be resuspended. As a result, the underwater light condition was greatly improved in RII and then promoted phytoplankton growth. ...
Article
The interpretation of environmental effect on phytoplankton growth is not straightforward, especially in ecosystems with high variation in hydrological conditions due to confounding variables. Lake Poyang is characterized by high fluctuation of water level (WL) due to its free connection to the Yangtze River. High frequency (weekly) and long-term (2009–2018) samplings were conducted in Lake Poyang resulting in 170 samples. Our study aimed to illustrate that whether the key factors determining phytoplankton growth change with WL. Furthermore, the impact of WL on phytoplankton was also detected. Six periods were classified in our study, i.e., dry season, raising period (I and II), wet season, and falling period (I and II) based on WL variation. Environmental characteristics were significantly (P < 0.01) different among these periods with the exception of orthophosphate. Based on the whole data set, water temperature (WT) was the critical parameter affecting phytoplankton growth. However, according to time series analysis, the key factors varied in different periods. Underwater light condition, which was represented by Secchi depth (SD), was the most critical factor controlling phytoplankton growth, especially in the periods with relatively high WL and WT (i.e., raising period II, wet season, and falling period I). The role of water temperature on phytoplankton was more evident in falling periods. In dry season with the lowest WL, total phosphorus limited phytoplankton growth. Regarding WL, its impact on phytoplankton was mainly through change in environmental parameters, such as water flow velocity, water transparency, and nutrients. Furthermore, time series analysis well simulated phytoplankton chlorophyll a in Lake Poyang, with larger R²adj (except raising period II and falling period II) and lower model error in all 6 periods. Our results revealed that the critical factors controlling phytoplankton growth were various with WL. Additionally, time series analysis will benefit local water resource management.
... The Smagorinsky factor of eddy viscosity ( C s = 0.28) and Manning numbers ( M = 10-59 m 1/3 /s) were used to represent heterogeneous bed roughness for the lake flow channels and the floodplains (e.g., vegetation area, mudflat, and permanent waterbody) of the flood pulse system ( Li et al., 2020b ). The model adopted the depth rule h drying (0.005 m) < h flooding (0.05 m) < h wetting (0.1 m) to capture the wetting and drying cycle in the floodplain system ( DHI, 2014 ;Li et al., 2014 ). To maintain the target Courant-Friedrich-Levy number of 1.0, the minimum and the maximum time step were set to 0.1 s and 3600 s, respectively. ...
... Extensive validation and applications in many previous studies have been conducted for the hydrodynamic model of the Poyang Lake-floodplain system (e.g., Li et al., 2014 ;Li et al., 2017Li et al., , 2019aLi et al., , b , 2020a. Therefore, a brief description regarding the theoretical basis and other model aspects of the MIKE 21 is given in this section. ...
Article
Recent years, the hydrological connectivity has gained popularity in various research fields, however, its definition and threshold effects at a system scale have not received adequate attention. The current research proposes a promising framework to refine the concept of surface hydrological connectivity by combining hydrodynamic modeling experiments, threshold effects and geostatistical connectivity analysis, exemplified by the flood-pulse-influenced Poyang Lake floodplain system (China). To enhance the inherent linkage between hydrological connectivity and eco-environments, total connectivity (TC), general connectivity (GC), and effective connectivity (EC) were proposed to refine the metrics of hydrological connectivity. The results show that substantial differences between the three connectivity metrics are observed for all target directions, demonstrating that the joint role of water depth and flow velocity may produce more dynamic and complex influences on EC than the other two metrics of TC and GC. Topographically, the connectivity objects/areas within the flood pulse system reveal that the floodplain is a more sensitive area than the lake's main flow channels under different connectivity conditions. The modelling experimental studies show that variations in water depth thresholds are more likely to have a strong effect on connectivity for the dry, rising, and falling limbs, rather than the flooding period, while the flow velocity may exert an opposite threshold effect. The lake-floodplain system is characterized by dynamic threshold behavior, with seasonally varying water depth and velocity thresholds. This study highlights the importance of redefined connectivity concept for facilitating scientific communication by combining hydrodynamic thresholds and offering recommendations for future connectivity assessments using our proposed metrics of TC, GC, and EC.
... To obtain the spatiotemporal fluctuations of the water regime in Poyang Lake, a numerical model was implemented based on the Delft3D-Flow model, which has been widely applied in simulations of flows, sediment transports, and water quality of shallow waters (Delft Hydraulics, 2014). As a shallow and wide lake, vertical currents in Poyang Lake can be neglected (Lai et al., 2011;Li et al., 2014;Zhang et al., 2015a, b;Yao et al., 2018). Thus, a 2D free-surface hydrodynamic model was constructed. ...
... The model parameters were initially defined based on literature values (Delft Hydraulics, 2014;Li et al., 2014;Zhang et al., 2015a;Qi et al., 2016;Li et al., 2016;Yao et al., 2018;Liang et al., 2019;Lu et al., 2019). The critical parameters were calibrated and validated by comparing the simulation values and measurements. ...
... Within the lake-floodplains, the flow velocities range between 0.1 and 1.0 m/s [31] and the associated residence time vary from~20-300 days [32]. The catchment rivers and the Yangtze River play a joint role in affecting the hydrological system, leading to different connectivity conditions between the lake and the adjacent floodplains (i.e., west-east direction) [33,34]. ...
... Within the lake-floodplains, the flow velocities range between 0.1 and 1.0 m/s [31] and the associated residence time vary from ~20-300 days [32]. The catchment rivers and the Yangtze River play a joint role in affecting the hydrological system, leading to different connectivity conditions between the lake and the adjacent floodplains (i.e., west-east direction) [33,34]. ...
Article
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Knowledge of dam construction in floodplain systems and its hydrodynamic effects plays a critical role in managing various kinds of floodplains. This study uses 3D floodplain hydrodynamic modeling to explore the possible effects of a proposed hydraulic project in Poyang Lake (PLHP) on the hydrodynamics, exemplified by a large floodplain system. Simulations showed that the water levels across most lake regions presented more significant changes than in the floodplain areas during the study period. The increased water levels upstream from the PLHP (~1.0 m) were distinctly higher than that downstream (~0.1 m). The PLHP may decrease the magnitude of the water velocities in the main channels of the lake, whereas velocities may experience mostly minor changes in the floodplains, depending upon the altered flow dynamics and transport. On average, the water temperature may exhibit mostly minor changes (~<1.0 °C) for both the horizontal and vertical scales within the flood-pulse-influenced lake system. Additionally, the model results indicated that the outflow process caused by the PLHP may be altered from the natural discharge into the Yangtze River to frequent backflow events during the storage period, demonstrating the non-negligible effect of the PLHP on the water supply for the downstream Yangtze River in the future.
... At the same time, the United Nations Environment Programme (UNEP), the World Bank Poyang Lake and the adjacent area is a basin that is composed of different landform types, such as mountains, hills, plains and lakes. The elevation of the lake basin is generally high in the south and low in the north; the maximum elevation difference can be up to 13 m, and the average elevation difference between the south and north is about 6.5 m [33]. Taking Songmen Mountain between Duchang County and Wucheng Town of Yongxiu County as the boundary, Poyang Lake is divided into two lakes in the north and south; the southern part is wide and shallow, which is the main lake area; the northern part is narrow and deep, which is the waterway into the Yangtze River. ...
... Poyang Poyang Lake and the adjacent area is a basin that is composed of different landform types, such as mountains, hills, plains and lakes. The elevation of the lake basin is generally high in the south and low in the north; the maximum elevation difference can be up to 13 m, and the average elevation difference between the south and north is about 6.5 m [33]. Taking Songmen Mountain between Duchang County and Wucheng Town of Yongxiu County as the boundary, Poyang Lake is divided into two lakes in the north and south; the southern part is wide and shallow, which is the main lake area; the northern part is narrow and deep, which is the waterway into the Yangtze River. ...
Article
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Poyang Lake is a typical lake in the middle and lower reaches of the Yangtze River and is the largest freshwater lake in China. The habitat quality of Poyang Lake has been declining in recent years, leading to a series of ecological problems. An ecological risk evaluation, based on land use, is important in order to promote a coordinated development of land use and the ecological environment. In this paper, land use data from the Poyang Lake basin in the corresponding years are interpreted based on the images from the Landsat satellite mission in seven periods from 1980 to 2020. The lake surface and the 1 km lakeshore zone of Poyang Lake are extracted based on the interpreted land use data. Finally, the ecological service value per unit area of the area is measured by combining it with the Chinese terrestrial ecosystem service value equivalent table, and then with the value of each ecological factor and the value of the changes to land use type. The research results show that: (1) from 1980 to 2000, the lake area of Poyang Lake had an overall decreasing trend (the area slightly increased from 1980 to 1990); from 2000 to 2020, the lake area of Poyang Lake gradually increased (the area slightly decreased from 2015 to 2020). (2) The farmland, forest, grassland and desert areas gradually increased and the wetlands gradually decreased over 40 years; the area of the water body gradually increased from 1980 to 2010, and gradually decreased from 2010 to 2020. (3) The ecosystem service value of the lakeshore zone of Poyang Lake fluctuated around 15,000 × 106 Yuan from year to year.
... Comparisons based on observed images show that HSTAFM is more accurate than STARFM and FSDAF , but HSTAFM still requires validation over small seasonal isolated lakes and narrow river channels. In addition, the discrepancies between model and remote sensing derived surface water areas can be considerably large, despite Li et al. (2014) and Zhang et al. (2017b), who have shown good correlation between them. The knowledge gap of when, where and how model-remote sensing differences exist hampers their usage in various applications. ...
... In this study, remote sensing-based surface water results were compared to model-based results. The inundation depth of Poyang Lake (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) was simulated by the MIKE 21 model (DHI, 2007), which is a 2D depth-averaged hydrodynamic model implemented previously by Li et al. (2014). The model defines a total lake area of 3124 km 2 according to historical lake surface areas during periods with high water levels. ...
Article
Determining the spatiotemporal dynamics of surface water in a heterogeneous floodplain is difficult, especially for its surrounding isolated lakes. Seasonal inundation patterns of these isolated lakes can be misestimated in a hydrodynamic model due to their short and erratic appearances. A surface water time series of Poyang Lake having an 8-day revisit frequency with a 30 m spatial resolution from 2000 to 2016 was conducted for the first time. This study was produced with a modified hierarchical spatiotemporal adaptive fusion model (HSTAFM) by integrating both Landsat and MODIS data. Discrepancies between model-based surface water and remotely-sensed surface water were evaluated, and possible causes were discussed. Results show that the modified HSTAFM can better detect the water features of a floodplain, thereby providing more detailed information in an seasonal isolated lake system than the MODIS MOD13Q1 product. With the fusion product, we found that Poyang Lake evidently shrank after experiencing a longer low-water period after the impoundment of the Three Gorges Dam. A large proportion of these discrepancies (averaging 36%) between model-based and remotely-sensed surface water distributed in seasonal isolated lakes, mainly occurred during high-water level periods. Uncertainties in the hydrodynamic model might attribute to smaller defined lake boundaries, bathymetric variations, human disturbance, and unconsidered groundwater recharge/discharge. These results provide a new insight into the temporally continuous and spatially dynamic assessment of simulated surface water, which is essential for the future improvement in the hydrodynamic model.
... Recentes estudos tem acoplado modelos hidrológicos de base física com modelos hidrodinâmicos em lagos e reservatórios (Dargahi and Setegn, 2011;Debele et al., 2008;Li et al., 2013;Xu et al., 2007), principalmente para avaliar a complexidade dos processos hidrológicos que ocorrem na bacia e os efeitos no comportamento hidrodinâmico do lago, assim como o efeito das transformações bióticas e abióticas de nutrientes que ocorrem ao longo da água, desde a precipitação até seu armazenamento. Outros estudos têm avaliado o impacto de eventos meteorológicos de pequena escala, como a passagem de sistemas frontais (e.g. ...
... This study was limited due to the short time scale employed to assess the potential effect of land-use changes and river discharge on water levels, which is an advantage of this kind of coupled approach. Li et al. (2013) presented another example of the coupled modeling of lake-catchment dynamics. The authors evaluated the performance of a distributed catchment-hydrology model coupled with a lake hydrodynamic model in Poyang Lake (China) (basin total area: 162,000 km 2 ; lake water-surface area: 1000 -3000 km 2 ) using in-situ measurements of lake water level. ...
Thesis
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A gestão de recursos hídricos tornou-se cada vez mais complexa devido ao rápido crescimento sócio-econômico e as mudanças ambientais nas bacias hidrográficas nas últimas décadas. Modelos computacionais são importantes ferramentas de suporte na gestão de recursos hídricos e tomada de decisões devido a sua funcionalidade, provendo informações importantes sobre os principais processos físicos, químicos e biológicos, e permitindo melhorar o entendimento desses processos, os quais ocorrem em diferentes escalas espaciais e temporais. Na presente tese, o objetivo foi compreender o funcionamento hidrológico do sistema integrado bacia hidrográfica - lagoa, e os efeitos na hidrodinâmica do lago, utilizando como suporte o acoplamento da modelagem hidrológica - hidrodinâmica, e o uso de técnicas de sensoriamento remoto para o monitoramento de parâmetros de qualidade da água (e.g., clorofilaa, temperatura da superfície d’água e níveis da água). A área de estudo é a bacia hidrográfica da Lagoa Mirim, localizada no sul do Brasil, possuindo uma área total de 58.000 km2 (56% no Uruguai e o restante no Brasil). Foram propostos e testados modelos empíricos para estimativa de clorofila-a em um lago raso subtropical, baseados em imagens do sensor MODIS e técnicas estatísticas. Além disso, foi desenvolvido e avaliado o acoplamento da modelagem hidrológica-hidrodinâmica de grande escala e o sensoriamento remoto. O modelo hidrológico distribuído de grande escala MGBIPH acoplado com o modelo hidrodinâmico IPH-ECO foi utilizado para simular a bacia hidrográfica e os principais componentes hidrodinâmicos da Lagoa Mirim. O modelo mostrou bom desempenho quando comparado com observações de vazões, além de dados provenientes de sensoriamento remoto, através de altimetria espacial. As simulações mostraram importantes aspectos sobre a estrutura de fluxo, campos de velocidade e níveis d’água na lagoa, assim como a influência de grandes rios, forçantes externas como o vento (intensidade e direção) e o impacto do estressor antrópico (retiradas para irrigação) no sistema. As simulações permitiram avaliar aspectos relacionados com as variações espaciais e temporais (diurna, mensal, sazonal e inter-anual) da temperatura da superfície da água, a dinâmica dos fluxos de calor (sensível e latente) e os efeitos de eventos meteorológicos de pequena escala como frentes frias, os quais têm um impacto significativo sobre a temperatura superficial da água e os fluxos de calor na lagoa. Quanto aos modelos empíricos para estimativa de clorofila-a a partir do MODIS, os resultados mostram que um simples e eficiente modelo desenvolvido a partir de análise de regressão múltipla, apresentou ligeiras vantagens sobre os modelos de redes neurais artificiais, modelos multiplicativos não paramétricos e modelos empíricos (e.g., Appel, Kahru, FAI e O14a) usualmente utilizados na estimativa de Chl-a em ambientes aquáticos. Resultados também indicam que é inapropriado generalizar um único modelo desenvolvido a partir do conjunto total de dados, para estimar concentrações de Chl-a na lagoa, o que corrobora a heterogeneidade espacial na distribuição de Chl-a e as diferenças entre regiões (litoral e pelágica). A modelagem hidrológica-hidrodinâmica de grande escala apoiada por informação de sensoriamento remoto, mostrou ser uma abordagem promissora para o entendimento da estrutura e funcionamento de lagoas rasas de grande porte e longo prazo, úteis para a gestão integrada dos recursos hídricos.
... It is a onelayer model in the vertical so it can be applied for such shallow choked lagoons where stratification can be neglected. The model has been extensively and successfully applied to coastal lagoons all over the world (e.g., Li et al., 2014;Martinelli et al., 2010;Tahershamsi et al., 2009) and was previously selected for Egyptian coastal lagoons (e.g., Assar et al., 2016;Elshemy et al., 2016;Rasmussen et al., 2009). The MIKE 21 model solves the vertically integrated equations of continuity and momentum using implicit finite difference techniques with the variables defined on a space staggered grid. ...
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Coastal lagoons are particularly vulnerable to climate change, in particular, Sea Level Rise (SLR) due to their shallowness. Lake Burullus provides a variety of socio-economic services as the second largest coastal lagoon in Egypt. Recently, it has experienced significant ecological deterioration. Thus, its ecosystem is fragile in the face of anthropogenic induced changes. The main objective of the current study is to investigate the climate change impacts on characteristics of Lake Burullus. A depth averaged hydro-ecological modeling system, MIKE21, was applied to develop an eco - hydrodynamic model for the lake. The developed model was calibrated and verified for two successive years: July 2011 - June 2012 and July 2012 - June 2013. The model simulations exhibited good agreement with the measurements during the calibration and verification processes. Six different Regional Climate Models (RCMs) were compared, using six different statistical metrics, to determine the most accurate one for the study area. The required meteorological input, including surface air temperature, precipitation, and evaporation were derived from the selected RCM. The meteorological input was extracted for two different years in the 21st century considering one Representative Concentration Pathways (RCPs) scenario, based on the Intergovernmental Panel on Climate Change (IPCC) 5th Report. Regional SLR projections for the Mediterranean Sea for the selected RCP scenario and the two studied years were obtained. These future climate change estimates were used to modify the validated model of the lake. A sensitivity analysis was applied to assess effect of future climatic conditions and SLR, separately. The results revealed that the lake water depths will increase and it will be warmer and more saline. Significant spatial variability of the studied parameters under climate change forcing is expected. Consequently, climate change is going to restrict the lake’s ability to preserve the present-day species. An urgent management plan involving adaptation works, should be implemented to reduce such potential species losses in Egyptian lagoons.
... In these cases, a further model refinement could be implemented, and in the specific case of 2D fluxes, the inertial equations could be considered, since they have been successfully applied for the simulation of some shallow lakes with the LISFLOOD-FP (e.g., Neal et al. (2012); Rudorff et al. (2014)) and MGB (Lopes et al. 2018) models. Some researchers have also coupled 1D river models to 2D lake models (Dargahi and Setegn 2011;Li et al. 2014;Zhang et al. 2017;Lopes et al. 2018;Munar et al. 2018;Tanaka et al. 2018), or even to 3D ones (Wu et al. 2017). ...
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Large-scale hydrologic–hydrodynamic models are powerful tools for integrated water resources evaluation at the basin scale, especially in the context of flood hazard assess-ment. However, recent model developments have paid little attention to simulate reser-voirs’ hydrodynamics within river networks. This study presents an adaptation of the MGB model to simulate reservoirs as an internal boundary condition, enabling the explicit simu-lation of hydrodynamic processes along reservoirs and their interaction with upstream and downstream floodplains in large basins. A case study is carried out in the Itajaí-Açu River Basin in Brazil, which has periodic flood-related disasters and three flood control dams. The model was calibrated for the 1950–2016 period forced with daily observed precipita-tion. The adjustment was satisfactory, with Nash–Sutcliffe metrics between 0.54 and 0.84 for the 11 gauges analyzed and with flood frequency curves also well represented. Simula-tion scenarios with and without floodplains and reservoirs were performed to evaluate the relative role of these factors on flood control basin-wide through evaluation of simulated discharges, water levels and flood extent. Itajaí do Oeste tributary and Itajaí-Açu mainstem present major floodplain attenuation, while in Itajaí do Sul and Itajaí do Norte tributaries the main flood control occurs due to reservoir attenuation. Downstream from the dams, results indicated that the reservoirs reach their maximum discharge reduction capacity for 5- to 10-year floods, decreasing it for larger floods. The developed model may be very use-ful for operational uses as flood forecasting and coordinated reservoir operation studies, as well as to enhance the comprehension of flood dynamics at basin scale.
... Accurate simulation of lake water level is paramount for quantifying the effect of morphology changes on lake hydrology. Previously, in order to analyze the effects of catchment inflow and Yangtze River discharge on lake water level variations, Li et al. [24,25] constructed two models: a physically-based mathematical model using the MIKE 21 and a back-propagation neural network (BPNN) model. By comparing the model performance, they concluded that both modeling approaches obtain very high accuracies for lake water level simulation. ...
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In recent years, a dramatic decline in Poyang Lake water levels and a shrinking water surface have raised concerns about water security and the wetland ecosystem. Changes in bottom topography due to sand mining activities in the lake was supposed to be one of the influencing factors of these changes. In response to this issue, the current study analyzed the change of lake bottom topography from observed digital elevation model (DEM) data, and quantitatively assessed the spatial and temporal responses of lake hydrology based on the framework of the neural network and the sediment effect was examined afterward. Results showed a total volume of 11.54 × 108 m3/year (about 0.96 × 108 m3/year or 1.58 × 108 t/year sediment) in net change of lake bottom topography in recent years, among which 97% was directly exported by commercial sand mining. During the study period, 2000–2011, intensive sand mining extended the central part of Poyang Lake and widened and deepened the outflow channel of the northern lake. This great change of lake bottom topography caused an average annual increase of 182.74 m3/s of lake outflow and a decline of 0.23 m–0.61 m in water levels across the lake. However, lake water levels are not consistent and show remarkable spatial and seasonal differences. The effects of changes in lake bottom topography on lake hydrological processes continue to grow as sand mining activities in the lake continue. More research on the environmental impacts is required for sustainable management of the lake ecosystem.
... Due to the importance of daily lake area information, a number of methods, including field measurement, topographic analysis, hydrodynamic modeling, and remote sensing techniques, have been developed recently. For example, based on the measured topographic data of Poyang Lake, Li (2014) established a hydrodynamic model to simulate the water surface area of Poyang Lake, and the results show that the modeled lake area is in reasonably good agreement with the one obtained from remote sensing imagery [15]. Although with relatively high accuracy, the first three methods are labor intensive and costly. ...
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Dongting Lake, the second largest freshwater lake in China, is an important water source for the Yangtze River Basin. The water area of Dongting Lake fluctuates significantly daily, which may cause flooding and other relevant disasters. Although remote sensing techniques may provide lake area estimates with reasonable accuracy, they are not available in real-time and may be susceptible to weather conditions. To address this issue, this paper attempted to examine the relationship between lake area and the water levels at the hydrological stations. Multi-temporal water area data were derived through analyzing Moderate Resolution Imaging Spectroradiometer (MODIS) imagery using the Automatic Water Extraction Index (AWEI). Then we analyzed the inter- and intra-annual variations in the water area of the Dongting Lake. Corresponding water level information at hydrological stations of the Dongting Lake were obtained. Simple linear regression (SLR) models and stepwise multiple linear regression (SMLR) models were constructed using water levels and water level differences from the upstream and downstream hydrological stations. We used the data from 2004 to 2012 and 2012, respectively, to build the model, and applied the data from 2013 to 2015 to evaluate the models. Results suggest that the maximum water area of the Dongting Lake during 2000–2015 has a clear decreasing trend. The variations in the water area were characterized by hydrological seasons, with the annual minimum and maximum water areas occurring in January and September, respectively. The water level at the Chengjingji station, and water level differences between upstream stations and the Chengjingji station, play a major role in estimating the water area. Further, results also show that the SMLR established in 2012 performs the best in estimating water area of the Dongting Lake, especially with high water levels.
... In the present modeling study, the Manning number of the lake-floodplains (M = 10-59 m 1/3 /s; Table 1) were based on literature values from previous modeling calibration of Poyang Lake and other similar areas (Chow, 1959;DHI, 2014;Kiss et al., 2019). The Smagorinsky factor of eddy viscosity (C s = 0.28) was also derived from Li et al. (2014) and adopted to perform the hydrodynamic simulation and model validation. ...
Article
The present study uses a 2D floodplain hydrodynamic model in combination with hypothetical scenarios to investigate the coupled effects (or maximum contribution) of floodplain vegetation on the hydrodynamic behaviors of Poyang Lake (China), a flood-pulse-influenced river-lake system. Model simulations reveal that the influences of the floodplain vegetation on lake water levels, flow velocities and outflow discharges were stronger during the rising and receding water phases than during the flooding phase, indicating the interactions between vegetation and hydrology that vary with the floodplain seasonality. The addition of floodplain vegetation affects conveyance efficiency of the system, decreasing flow velocities by 0.2 m/s, increasing water levels by 0.3 m and associated storage volume of the lake by up to ∼5%. The distributed effect of floodplain vegetation on the flow velocities shows more complex and sensitive responses than the water levels across the lake-floodplains, demonstrating a strong linkage between the vegetation structure of the floodplain and the velocity distribution. Sensitivity analysis indicates that the transition between different vegetation cover types cannot produce significant influences on the hydrodynamic behaviors, relative to the coupled effects of floodplain vegetation. This study provides important knowledge regarding the role of floodplain vegetation changes to decision-makers for both Poyang Lake and other similar flood pulse systems, given proposals to cope with the flood risk and the accelerating pace of human interventions.
... We chose the Mike21 software by DHI [8] to solve the dynamic shallow-water equations numerically. Mike21 had been previously applied extensively, and successfully verified in many wind-driven coastal, estuarine and lake environments [19,22,27]. Therefore, we give only a brief description of the solver here, and for further details we refer to the model documentation [8]. ...
Article
We analyse the vorticity production of lake-scale circulation in wind-induced shallow flows using a linear elliptic partial differential equation. The linear equation is derived from the vorticity form of the shallow-water equation using a linear bed friction formula. The features of the wind-induced steady-state flow are analysed in a circular basin with topography as a concave paraboloid, having a quadratic pile in the middle of the basin. In our study, the size of the pile varies by a size parameter. The vorticity production due to the gradient in the topography (and the distance of the boundary) makes the streamlines parallel to topographical contours, and beyond a critical size parameter, it results in a secondary vortex pair. We compare qualitatively and quantitatively the steady-state circulation patterns and vortex evolution of the flow fields calculated by our linear vorticity model and the full, nonlinear shallow-water equations. From these results, we hypothesize that the steady-state topographical vorticity production in lake-scale wind-induced circulations can be described by the equilibrium of the wind friction field and the bed friction field. Moreover, the latter can also be considered as a linear function of the velocity vector field, and hence the problem can be described by a linear equation.
... Water flow velocity data were obtained from the 2D MIKE 21 hydrodynamics model for Poyang Lake . Li et al. (2014Li et al. ( , 2015 developed a 2D depth-averaged hydrodynamic model of Poyang Lake using MIKE 21 code to explore its water level, water surface area, and water flow pattern dynamics, and the MIKE 21 modeling system is considered to be appropriate for modeling the wide and shallow characteristics of Poyang Lake (Zhang et al. 2012Zhang and Werner 2015). ...
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Large river floodplain systems provide a variety of societal, economic and biological benefits and are undergoing extensive and intensive environmental deterioration. Eutrophication coupled with undesired harmful cyanobacterial blooms is one of the most widespread and severe problems in floodplain ecosystems. However, our knowledge about cyanobacteria, particularly the biogeography of N2-fixing (Nfix) cyanobacteria in shallow floodplain lakes, is very limited, and the relationships of cyanobacterial blooms with nutrient ratios and hydrological alterations remain unclear. We used a comprehensive database of field data compiled over several years (2012 to 2016) to compare the biomass and distribution of Nfix cyanobacteria between the northern (high water velocity) and southern (low water velocity) parts of Poyang Lake and to investigate the roles of hydrology and the critical nutrient mass ratios of total nitrogen:total phosphorus (TN:TP) and dissolved inorganic nitrogen:orthophosphate (DIN:PO4-P) as significant predictors of Nfix cyanobacterial biomass and distribution in eutrophic floodplain ecosystems. Dolichospermum spp. (Dolichospermum flos-aquae, D. azotica, D. circinalis, and D. spiroides) were the most widely distributed and frequent diazotrophic cyanobacteria in the regions considered in this study, followed by Aphanizomenon flos-aquae. The Nfix cyanobacterial biomass was generally low (mean = 0.32 mg/l) across Poyang Lake and was lower in the north than in the south. Using Spearman’s rank correlations, we found that this pattern may be attributed to the high turbidity and washout from the high velocity of water flow in the north. The filament length and heterocyst frequency of Dolichospermum spp. in the lake were also strongly linked to variations in hydrological characteristics and water temperature. Our results imply that the nutrient mass ratios are more important determinants of Nfix cyanobacterial biomass than hydrology in the south part of the lake. The critical TN:TP mass ratio for the Nfix cyanobacterial communities in Poyang Lake is approximately 20, and the critical DIN:PO4-P mass ratio in the lake is approximately 40. Our analysis provides new information regarding the occurrence of bloom-forming Nfix cyanobacteria in Yangtze River floodplain lakes and thus fills an important knowledge gap in subtropical freshwater ecosystems.
... In hydrodynamic mathematical modeling, bathymetric data are required to estimate storage and flow propagation across lakes. While level-area-volume relationships are used in lumped, simplified level-pool routing methods, the availability of bathymetric data allows a more complete description of the hydrodynamics of water bodies (Dargahi & Setegn, 2011;Fread, 1993;Li et al., 2014;Lopes et al., 2018;Munar et al., 2018;Zhang et al., 2017). For modeling river systems, channel bathymetry is also required and remote sensing-based methods have been proposed (Brêda et al., 2019;Domeneghetti, 2016;Durand et al., 2008;Moramarco et al., 2019). ...
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Topography is critical information for water resources management in lakes, and remote sensing provides a unique opportunity to estimate topography in ungauged regions. We introduce here a new method that estimates nearshore topography of water bodies based on a flood frequency map and time series of water levels by assuming the equivalence between flood frequency and water level exceedance probability at a given area. Test cases are performed for two lakes and 12 hydropower reservoirs using the proposed Flood2Topo app. This new application generates the bottom level pixel by pixel and level‐area‐active storage relationship directly from the topography map, without the need to fit functions. Flood extent estimates from the Landsat based Global Surface Water (GSW) data set, the current state‐of‐the‐art, were used to run Flood2Topo, together with water levels from satellite altimetry and in situ gauges. Results show bottom level root mean square deviation (RMSD) values of 18.5 and 146 cm for Lake Poopó (Bolivia) and Lake Curuai (Amazon basin), respectively. For reservoir active storage, RMSD normalized values ranged from 2% to 11% for 11 reservoirs (average NRMSD of 6.4%). The method can be applied to any seasonally flooded area using any data set. Considering the surface water occurrence map from the GSW data set, the method is applicable to 35.8% (86%) of the global seasonally flooded areas delimited by flood frequencies between 0 and 95% (99%) over 35 years. The flood frequency‐based method is a promising tool for obtaining data for hydrodynamic simulations and monitoring of ungauged water bodies.
... Muskingum-Cunge routing) may be implemented for the whole basin or for only part of it, for which kinematic routings are usually sufficient Follum et al., 2017;Getirana, Peters-Lidard, et al., 2017;Paiva et al., 2013). An optimum setup is likely related to a 1-D-2-D coupling strategy (Andreadis et al., 2017;Hoch, Neal, et al., 2017;Hodges, 2013), for example, the hybrid model systems used to represent river-lake modeling systems (Dargahi & Setegn, 2011;Li et al., 2014;Lopes et al., 2018;Munar et al., 2018;Tanaka et al., 2018;Zhang et al., 2017), and adaptive model meshes are also promising (Hoch, Haag, et al., 2017). In the case of the Negro basin, a 1-D river-floodplain simulation could be performed for most of the basin and 2-D mainly for the interfluvial wetlands and the large floodplains around Negro mainstem (in the case that other output variables than discharge are required). ...
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Recent years have seen the development of 1D and 2D regional scale hydrological-hydrodynamic models, which differ greatly from reach scale applications in terms of subgrid assumptions, parameterization and applied resolution. Although 1D and 2D comparisons have already been performed at reach and local scales, model differences at regional scale are poorly understood. Moreover, there is a need to improve the coupling between hydrological and hydrodynamic models. It is addressed here by applying the MGB model at 1D and 2D dimensions for the whole ~700,000 km² Negro Basin (Amazon), which presents different wetland types. Long term continuous simulations are performed and validated with multi-satellite observations of hydraulic variables. Results showed that both approaches are similarly able to estimate discharges and water levels along main rivers, especially considering parameter uncertainties, but differ in terms of flood extent and volume and water levels in complex wetlands. In these latter, the diffuse flow and drainage patterns were more realistically represented by the 2D scheme, as well as wetland connectivity across the basin. The 2D model led to higher drainage basin-wide, while the 1D model was more sensitive to hydrodynamic parameters for discharge and flood extent, and had a similar sensitivity for water levels. Finally, tests on the coupling between hydrologic and hydrodynamic processes suggested that their representation in an online way is less important for tropical wetlands than model dimensionality, which largely impacts water transfer and repartition.
... For more details on the hydrology of the system, the interested reader is referred to the relevant publications, e.g. Li et al., 2014 andGuo et al., 2008. According to the Chinese Environmental Quality Standards for Surface Water (GB3838-2002), Poyang Lake has an overall water quality that is better than most other large Chinese Lakes, such as Tai Lake or Chao Lake (Fig. 9). ...
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We propose a visualisation framework for data exploration, analysis and presentation of complex hydrological studies in large catchments. This furthers a deeper understanding of the interrelations between the included datasets, allows for discussions among researchers from different disciplines and is the basis for illustrating complex phenomena to stakeholders or the interested public. Based on the 162,000 km² catchment of Poyang Lake, the largest freshwater lake in China, we developed a Virtual Geographic Environment that combines a wide range of 2D and 3D observation data sets with simulation results from both an OpenGeoSys groundwater model and a COAST2D hydrodynamic model visualising water and solute dynamics within and across hydrologic reservoirs. The system aims for a realistic presentation of the investigation area and implements approaches of scientific visualisation to illustrate interesting aspects of multi-variate data in intuitive ways. It employs easy-to-learn interaction techniques for navigation, animation, and access to linked data sets from external sources, such as time series data or websites, to function as an environmental information system for any region of interest.
... The performance of the model in understanding the pattern of flood inundation showed satisfactory results compared with the remote sensing imageries. In a recent study, Li et al. (2014) incorporated the MIKE 21 and remote sensing approaches to study the hydrodynamics of a lake watershed in China and suggested that the model is applicable to simulations of river hydraulics and flood inundation. ...
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Increasing urbanization has led to diminished agricultural mainland for food production worldwide. Riverine sandbars could be viewed as prospective landmasses which could act as additional agricultural lands. The present study emphasizes sandbar area availability and the scope of utilizing these landmasses through geospatial techniques, modelling studies and questionnaire surveys. Satellite images were derived at decadal scales to determine the change in the land-use land cover (LULC) within the Brahmaputra River in Assam, India. The fluctuations in the landmasses under different streamflow conditions were derived using a hydrodynamic model. The results showed that the percentage of vegetated sandbars has increased from ~27.36% in 1976–1980 to ~44.67% in 2016–2017, and consecutively, the percentage of non-vegetated sandbars has decreased from ~51.18 to ~30.93%. Furthermore, it was found that the area under cropland and vegetated sandbar varied seasonally. To further understand the utilization of these resources, a socioeconomic survey with a structured set of questions was conducted at various sandbars. The survey revealed various aspects of economic benefits, practices of sandbar cultivation, beneficial produce, difficulties faced, and willingness among farmers to expand sandbar cultivation. Coupling the prevailing traditional knowledge of cultivation among the farmers with scientifically derived information obtained from satellite data and mathematical model simulations can lead to a more systematic utilization of the ecosystem. Thus, the study shows the immense potential of utilizing the sandbars of large rivers to sustain food demands, alongside developing links between land-use change, ecosystem behavior, and socio-economic development.
... The simulation indicated that near-surface velocities were affected by the wind conditions and they matched the predominant wind directions. Li et al. [19] developed a hydrodynamic model and a distributed catchment hydrological model to simulate spatial water level differences in Poyang Lake, China. The results revealed a satisfactory agreement with field observations, and both models accurately simulated seasonal changes in the lake surface area. ...
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A three-dimensional (3D) numerical model was developed to investigate the thermodynamic and sediment processes in a subtropical drinking water reservoir. Data-driven models were also established to generate the inflow conditions. The modelling outputs revealed that climatic forces such as storms and winds significantly impact lake stratification and mixing processes. The sediment transport is driven by storm events, during which sediment delivery to the reservoir is dominated by allochthonous flux. The sediments are transported from riverine zones to transition zones and finally to lacustrine zones. It is estimated that sediment accumulation could have reached 100,000 kg during the largest storm event in February 2015. The winds can lead to a strong vertical water cycle, especially at the centre of the reservoir, and strong winds result in bed erosion in shallow regions. The outcomes of this paper benefit future research by providing a modelling approach for understanding the hydrodynamics of lakes and reservoirs under a variable climate, and also the local water utility by providing insights for an improved management of the reservoir of this study.
... Lake DT has a drainage area of 257,000 km 2 , and the average yearly runoff from outlets is 3021 × 10 8 m 3 . The large floodplain regions of lake DT and PY are included in the "Ramsar Convention on Wetlands of International Importance Especially as Waterfowl Habitat" [20]. Lake JS was once a part of lake PY but was isolated from the main channel by a dam in 1959. ...
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Flood pulse related physical variables (FLOOD) can affect zooplankton community structure through local factors directly and can also influence through regional dispersal factors of metacommunity concepts indirectly. Therefore, we infer that spatial patterns of zooplankton communities could be related to metacommunity concepts and their importance may depend on the size of the aquatic/terrestrial transition zone (ATTZ). Herein, we explored the relative importance of limnological (LIMNO) and FLOOD variables in zooplankton community by analyzing data from 272 sites across three floodplain lakes in the middle reaches of the Yangtze River. Our results showed that the variation in the zooplankton community can be well explained by the LIMNO and FLOOD variables in all of the lakes under the low water level season. However, during the high water level season, neither LIMNO nor FLOOD can explain the spatial variances of zooplankton. Therefore, our results indicated that testing biogeographical theories and macroecological laws using zooplankton should consider temporal aspects of flood pulse. Furthermore, we noted that the number of explained variance by local variables is negatively correlated with the size of the ATTZ. Metacommunity concepts provide complementary insights in explaining zooplankton spatial patterns within large floodplain systems, which also provide a theoretical basis for ATTZ protection in floodplain management.
... In addition, HCs were created by identifying the area by water depth, and the storage capacity using reservoir topographic information; thus, the topographic and morphological characteristics of these basins were identified and used as basic data [20][21][22][23]. The morphology index and HC are important information for researching reservoir topographic characteristics, and studies are required to quantitatively investigate topographic characteristics [24][25][26][27][28][29][30][31]. ...
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The impact of irrigation reservoirs requires investigation through hydrological analysis to identify the flood control functions of these reservoirs. However, there is insufficient information concerning important geographical, morphological, and topographic characteristics, such as the reservoir cross-section. Therefore, this study aimed to identify the morphological and topographic characteristics of reservoirs using geographical information instead of measurement data. Ten reservoirs, including the Ga-Gog reservoir located in Miryang City, South Korea, were selected. The topographic information of the reservoirs was obtained using topographic maps and GIS techniques. Based on this information, the volume (V)-area (A)-depth (H) relationship and the hypsometric curve (HC) according to the relative area (a/A) and relative height (h/H) were created. A comparison of the reservoir volume, estimated using topographic information, with the measured volume revealed an error rate between 0.23% and 14.27%. In addition, two collapsed reservoirs located near Miryang City were investigated by creating V-A-H relationships and HCs using topographic information. The morphological characteristics of the reservoirs were identified by analyzing the (1) morphology index, (2) full water storage area-levee height relationship, and (3) full water storage area relationship. The analysis results showed that the collapsed reservoirs had high water depth and a large area relative to other reservoirs. Similar types of reservoirs were grouped by conducting a cluster analysis using basic properties such as the basin area, storage, and levee height. The cluster analysis results, based on HC analysis, grouped the reservoirs into three shapes: convex upward (youthful stage), relatively flat (mature stage), and convex downward (old stage). The HCs of the collapsed reservoirs exhibited a convex downward shape, indicating that they were subjected to considerable erosion due to aging. Moreover, this considerable erosion caused a large quantity of sediment to accumulate in the reservoirs, resulting in an insufficient allowable storage capacity of the reservoir because the flood control capacity was reduced, which may have led to their collapse during heavy rainfalls. Therefore, the identification of potential causes of reservoir collapse through the morphological characteristics and HCs of reservoirs are expected to support the operation and management of reservoirs to reduce flood damage.
... Geographic location and extent of the study area in Poyang Lake Jiangxi Province, People's Republic of China. S.Yao, et al. Ecological Indicators 117 (2020) 106556 determining which grids could participate in the calculation.(Li et al., 2014). Therefore, this model was chosen to calculate the hydroperiod of Poyang Lake; 1998, 2002 and 2010 were used as typical wet years;2006, 2007 and 2011 were used as typical dry years; 2000, 2008 and 2009 were used as typical normal flow years(Lai et al., 2017;Yang et al., 2018). ...
Article
Migratory birds are indicator organisms for the health of wetland ecosystems. Choosing the key environmental indicators is vital to the assessment of habitat suitability for migratory birds. In the study, hydroperiod was used to predict wetland suitability for migratory birds. It control growth of vegetation used for migratory birds’ food and could predicted by hydrodynamic model. This study presents a new indicator for assessing migratory bird habitat suitability in wetland, continuous flooding time (CFT), based on two-dimensional (2D) hydrodynamic model and vegetation growth threshold. In Poyang Lake wetland (the largest migratory bird wintering based in Asia), variation in CFT amongst different hydrological years (wet, dry and normal flow years) was calculated by using the 2D hydrodynamic model based on incompressible Reynolds Average Navier-Stokes (N-S) equation. The habitat suitability for migratory birds were calculated based on the vegetation growth threshold (CFT) of Carex spp., Phalaris arundinacea and Polygonum criopolitanum in the typical (hydrological) years. Results show that migratory birds have the largest suitable area (with High and Very High suitability) in 2009 (normal flow year). The suitable area in severe drought (flood) year is significantly less than the area in normal dry (wet)year. The average of the suitable CFTs (with High and Very High suitability) are almost equal in 2007 (dry year) and 2002 (wet year). The suitable CFT is between 120 and 240 days, and the average of the suitable CFT is 170.39, 190.26 and 173.49 days in 2007 (dry year), 2009 (normal flow year) and 2002 (wet year), respectively. Overall, the study provides a valuable evaluation indicator of habitat suitability for migratory bird, however the use of the indicator must depend on a certain study of the vegetation growth threshold and the feeding habit of migratory birds for the study area. The proposed indicator can further improve the comprehensive evaluation system for wetland migratory birds and provide a scientific reference of the water environment planning and ecological management for the scheduled Poyang lake dam.
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Poyang Lake, the largest freshwater lake in China, plays a key role in regulating the hydrology, water quality and ecosystem in the middle reaches of the Yangtze River. Recent industrialization and urbanization in Jiangxi province have led to rapid increase in water consumption and water quality deterioration. In this research, a numerical model is developed to simulate the hydrodynamics and water quality evolutions in Poyang Lake and its surrounding river network. The study links an in-house one-dimensional river network model with a MIKE multi-layered three-dimensional hydro-environmental model. The validated model is used to investigate the impact of a proposed downstream barrage on Poyang Lake's flow and ecosystem. All of the five considered barrage operation schemes demonstrate the capability of increasing the water level and inundation area during the dry period, especially in the lake's downstream region. The barrage schemes help reduce the lake's nutrient concentrations, due to the enhanced dilution at higher water levels. Nonetheless, the barrage leads to DO depletion which could pose a threat to the aquatic wildlife and habitats. This study's findings contribute to a better understanding of the hydro-environmental influence of the proposed barrage and thus the optimisation of its operation to mitigate the adverse influence. HIGHLIGHTS A hybrid model is developed for the hydro-environmental simulation in Poyang Lake basin and its associated rivers.; Investigation of the hydro-environmental impact of the Poyang Lake barrage using the validated hybrid model.; The barrage increases the water level and inundated area but reduces nutrient and DO concentrations.; Negative influences of the barrage can be limited by optimising the barrage operation.;
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Floodplains play a significant role in affecting the transport of water, dissolved matter and sediments during wide-ranging drying and wetting. This study uses a hydrodynamic model and geostatistical method to explore the variations of water storage and its relationship with the surface hydrological connectivity, exemplified by the large Poyang Lake-floodplain system (in China). The simulations show that the floodplain storage exhibits largely similar behavior to that of the total lake water storage, but the water storage in the main lake is distinctly higher than the floodplains. The lake storage is estimated to be from 20 × 10⁸ to 163 × 10⁸ m³ and differs considerably between seasons, and the contribution of the floodplain to the total lake storage varies from 18 to 34%. Geostatistical analysis reveals that the degree of surface hydrological connectivity can be classified as high connectivity in summer, low connectivity in winter, and intermediate connectivity during other seasons. Higher variability of water storage and lower frequency of hydrological connectivity are found in the seasonal floodplains, whereas the lower variability and higher frequency are observed in the main lake, indicating that water storage is inextricably linked to the dynamic behaviors of surface hydrological connectivity. Additionally, the estimated water storage significantly increases from the low and intermediate conditions to the high connectivity condition, mainly due to the key process of the west–east connectivity in controlling lake-floodplain interactions. This study improves understanding of Poyang Lake floodplain behavior and other similar floodplain systems by providing knowledge of water balance, water allocation and water management. Graphic abstract Open image in new window
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Groundwater and surface water are hydrologically interconnected systems that exhibit dynamic water, heat and mass exchanges. In this study, a conceptual framework was used to investigate groundwater behaviors and associated hydrological exchanges by combining field measurements, digital filtering and analytical approaches, exemplified by a linked catchment-floodplain-lake system (Poyang Lake, China). The results show that the hydrological regime for both groundwater and surface water exhibit a seasonal variability in the lake catchment. Topographically, the lake catchment can be divided into the mountainous baseflow, ungauged lateral groundwater and floodplain groundwater that contribute to the lake storage changes. Although groundwater flow is generally from the mountainous catchment to the lake floodplain areas due to topographic effects, precipitation provides an additional input for the shallow groundwater and is expected to enhance the groundwater dynamics in terms of spatially heterogeneous responses. The estimation indicates that about 40 % of the catchment river discharge may be coming from the mountainous baseflow (~290 × 10⁸ m³/yr) and discharged into the lake through a surface flow pathway. The ungauged groundwater-lake interaction shows the annual discharge volume is up to 10 × 10⁸ m³/yr and associated exchange fluxes tend to be stronger during spring-summer months (23–45 m³/s) than those of autumn-winter months (9–22 m³/s). Additionally, the floodplain groundwater-lake exchange (~9.5 × 10⁸ m³/yr) indicates that groundwater generally receives the lake water during summer months (mean flux = 110 m³/s) and discharges into the lake during other months (90 m³/s) through a subsurface pathway. This study highlights the importance of groundwater's contributions to the surface river-lake system in terms of the flux variability and different transport pathways. The outcomes of this work will benefit future water resources management and applications by providing a methodology for predicting the groundwater hydrology of large lake-catchment systems.
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Topography determines the nature of hydrodynamic processes and its changes potentially affect the water quantity and quality. This study assessed the spatiotemporal impacts of topography changes on hydrological and hydrodynamic characteristics of China's largest freshwater lake, Poyang Lake. Results from simulation of different channel erosion intensities indicated that topography changes induced hydrological and hydrodynamic variations with spatiotemporal heterogeneity. Water levels in the lake decreased and the effect was enhanced with stronger erosion intensities. The decrease in water level was significant during the dry period, but negligible during the wet period. Water levels decreased by an average of 0.90-1.1 m in the northern channel during the dry period, and 0.27 m and 0.20 m in the central and eastern lakes during the rising and recession periods. The changing water level further affected the distribution of water with the effect of gathering water to the channel from nearby areas. Moreover, channel erosion altered the lake-river interactions. During the dry period, outflow discharges increased as the channel conveyance capacity increased by 25-136%. In contrast, during the wet period, outflow discharges decreased as the inflow regulation volume increased by 3.8-8.2 × 10 8 m³. Particularly, backflow frequency and volume increased during the flooding period of the Yangtze River. In addition, the dry period in Poyang Lake was extended, and the frequency of low-water events increased significantly. This study demonstrated the spatiotemporal impacts of topographical changes on hydrodynamic processes in Poyang Lake, therefore providing a better understanding of variations in water regimes and lake-river interactions.
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Seasonal lakes that exist in floodplain settings have significant effects on hydrological and ecological processes and are highly susceptible to various changes; however, they are rarely investigated, mainly because of the large extent and remoteness of floodplains. This study uses physically based hydrodynamic modeling in combination with a bathymetry adjustment approach to investigate the coupling effects of 77 seasonal lakes (defined as the seasonal lake group) on hydrological behaviors within the Poyang Lake-floodplain system (China) from a systemic perspective. Elucidation of the role of seasonal lake groups could benefit from hydrodynamic modeling, which enables complex lake-floodplain simulations and comparison analyses of natural (original bathymetry) and hypothetical conditions (adjusted bathymetry). In the present study, the simulation results showed that the temporal influences of the seasonal lake group on water levels, lake outflows, and inundation dynamics were greater during dry seasons than wet seasons for both the dry (2006) and wet years (2010). The spatial effects of the seasonal lake group on the hydrology of the lake’s floodplains were stronger than those of the main lake for both hydrological years. The findings demonstrate that the seasonal lakes are likely to have very limited effects on the main lake and the associated flood levels. On average, the role of the seasonal lake group during the dry seasons was around several times stronger than that during flood seasons in terms of the magnitudes of hydrological responses. Additionally, it is expected that the seasonal lake group may exert an important role in influencing the surface hydrological connectivity and associated dry-wet hydrological shift across lake-floodplains, indicating a dominant role of the floodplain bathymetry changes. Overall, the results of this study will support management and planning of Poyang Lake and other similar floodplain regions with numerous small, shallow, and seasonal lakes by providing more reliable information regarding bathymetry changes, water management and lake-floodplain interactions to decision-makers for improved floodplain protection strategy.
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Because of the high spatial heterogeneity of the ecosystem properties of large lakes, the characterisation of lake zones is particularly helpful for designing zone-specific strategies for water management practices. In this study, we developed a lake-zoning framework by investigating the lateral dispersion of inflow pollutants through dye-tracking experiments in a case study of a large shallow lake (Lake Chaohu) in China. A two-dimensional hydrodynamic and mass transport model was used to quantify the impacts of inflow rivers on this lake. Results from 2012 to 2014 showed that the lake zoning results were more stable at the annual scale than at the seasonal scale, implying that the seasonal scale is not suitable for the establishment of lake zones. A driving factor analysis showed that inflow discharge was a more critical factor determining lake zones than wind conditions. In contrast to previous lake zoning methods, the proposed framework implements lake zoning quantitatively through hydrodynamic modelling.
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This study outlines a framework for examining potential impacts of future climate change in Poyang Lake water levels using linked models. The catchment hydrological model (WATLAC) was used to simulate river runoffs from a baseline period (1986–2005) and near-future (2020–2035) climate scenarios based on eight global climate models (GCMs). Outputs from the hydrological model combined with the Yangtze River's effects were fed into a lake water-level model, developing in the back-propagation neural network. Model projections indicate that spring–summer water levels of Poyang Lake are expected to increase by 5–25%, and autumn–winter water levels are likely to be lower and decrease by 5–30%, relative to the baseline period. These amounts to higher lake water levels by as much as 2 m in flood seasons and lower water levels in dry seasons in the range of 0.1–1.3 m, indicating that the lake may be wet-get-wetter and dry-get-drier. The probability of occurrence for both the extreme high and low water levels may exhibit obviously increasing trends by up to 5% than at present, indicating an increased risk in the severity of lake floods and droughts. Projected changes also include possible shifts in the timing and magnitude of the lake water levels.
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Lakes and river-related floodplains are hydrologically complex and dynamic systems that exhibit frequent wetting and drying. Poyang Lake and its extremely productive wetland constitute the largest lake-floodplain system of the Yangtze River basin. This study aims to use a daily water balance model in combination with a physically based hydrodynamic model to investigate the overall hydrological regime of the lake-floodplain system. Water balance analysis shows that 79.0% and 12.2% of yearly inflows are from river discharges from the upstream gauged and downstream ungauged catchments, respectively. The direct precipitation contributes around 3.0% on the lake surface, while the balance of 1.2% is sourced from floodplain runoff (0.5%) and lake's backflow (0.7%). Around 86.9% of the total lake outflow is discharged into the Yangtze River, while 1.5% evaporates for the lake water surface. Net groundwater discharge (11.6%) has greater impacts on the water balance than the net groundwater recharge (4.6%). Water balance results highlight that the catchment rivers and the associated groundwater system are important parts of Poyang Lake. In general, the catchment rivers exhibit higher flashiness during the rising and flood periods than the other periods, and the flashiness in the lake downstream and floodplains is higher than in the lake upstream regions and the main lake, respectively, demonstrating spatiotemporal variability in the flood pulse in the lake-floodplain system. This study contributes to provide more detailed information regarding hydrological components and their relative effects to decision-makers for both Poyang Lake and other similar floodplains, given proposals to cope with the climate and human interventions and the accelerating pace of water resources and water safety management.
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Study region Poyang Lake, the largest freshwater lake in China, is connected to the Yangtze River and has been undergoing shrinkage over the past decade. Study focus The Poyang Lake water control project (PLWCP) was proposed to protect the lake against rapid shrinkage. However, the quantitative impact of the project on the floodplain inundation regime is not yet clear. This study used a hydrodynamic model to quantify the influence of the PLWCP on the inundation regime of upstream floodplains in Poyang Lake. New hydrological insights for the region Poyang Lake was characterised by high spatiotemporal heterogeneity in inundation patterns and that the northern lake areas were most affected, followed by the central and eastern lake areas. The western and southern lake areas were less affected. The water levels of the northern channels increased by a maximum of 4–5 m during the first recession period (16 Sep–31 Oct) and increased by 1–2 m during the impounding period (1 Sep–15 Sep). Most of the lake areas except the northern channels showed a water level increase of less than 0.5 m from November to March. The increased inundation areas were mostly 100–400 km² (<20%) and reached greater than 800 km² (~30%) from September to October, of which over 300 km² (10%) lasted approximately 2 months. Potential suitable habitats in the northern, central and eastern lakes might be impacted.
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Changes in the timing of extreme precipitation have important ramifications for public safety and storm water management, but it has not received much attention in relation to flooding. This study analyzed the changes in the timing of extreme precipitation in the Poyang Lake basin and projected its future changes for the period 2020–2099. The study also quantified the influences of changes in the timing of peak flows on lake floods based on a hydrodynamic model. The results showed that peak rainfall in the Poyang Lake basin had occurred on later dates during the period 1960–2012, and it is this change that caused a delay in peak streamflows from five rivers in the lake basin. Moreover, the effects of these changes are expected to be more prominent during 2020–2099; for example, the rate of delay will be about 2.0 days per 10 years both for peak rainfall and for streamflow in the Poyang Lake basin. The hydrodynamic simulation further showed that a delay of peak streamflows from five rivers would significantly increase the flood level and outflow of the lake and also prolong the duration of floods. These results indicate that the risk of floods in Poyang Lake is likely to increase in the future, therefore making flood control in this region more challenging. HIGHLIGHTS Peak rainfall in the Poyang Lake basin had occurred on later dates.; This delay in peak rainfall, in turn, caused a delay in the peak runoff in the local basin and increased the chances of flooding.; There is a delay in the timing of the projected future peak rainfall during the period 2020–2099.; The delay in peak flows has further increased the highest lake level and the duration of floods.; The risk of floods in Poyang Lake is likely to increase in the future.;
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Watershed anthropogenic activities, including pollutant discharge, sand mining, and upstream reservoir operation, have increased nutrient loads and decreased water levels and sediment concentrations in Poyang Lake, and thus affected the aqueous ecosystem. In this study, we developed an ecological model from the framework of AQUATOX to simulate the physical, chemical, and biological evolution of Poyang Lake under watershed anthropogenic influences, and used model output for a multidimensional ecosystem assessment of ecosystem structure, function, service, material flow, temporal dynamics, and collapse probability. The potential impacts of a proposed Poyang Lake water conservancy project (PYWCP) to build a sluice near the outlet of Poyang Lake to regulate lake level were explored. Results show that the watershed anthropogenic activities have worsened the Poyang Lake ecosystem. Specifically, the phytoplankton biomass increased, while benthos and fish decreased; the exergy, capacity of nutrient change, and the total biomass-gross primary production ratio decreased; as the lake's volume decreased, fishes’ trophic levels and food web robustness decreased, the food web shrank, single species dependence increased, and ecosystem stability decreased. The PYWCP could mitigate most of these effects, however, it would not recover Poyang Lake to historical conditions, and close monitoring with attention to sluice operational scheduling are required.
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The Mirim and Patos Lagoons form the largest lagoon complex in South America. Wind is one of the dominant climatic elements of circulation and water levels in the basin. Therefore, we aimed to better understand the effects of wind on the Mirim–São Gonçalo watershed by applying the MGB hydrological model and to assess whether it would produce satisfactory results for modeling. Various tests were performed to determine the best representation of the processes involved and the observed levels. The best results were obtained with the inclusion of sub-daily wind data in the simulation and also the downstream boundary condition by using the observed water level data at the sluice dam of the São Gonçalo channel. The results showed that the model could successfully simulate the levels and demonstrated the importance of including the wind when modeling the hydrodynamic processes of large lake environments. HIGHLIGHTS What is the numerical effect of introducing wind influence in the inertial flux propagation method?; What are the optimal values of the coefficient of wind friction and parameterization for minibasin connections to obtain the best simulation of the lagoon?; Does the inclusion of lock level information in the SGC as a downstream boundary condition and hourly winds benefit the level representation?;
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River–lake water exchange reflects hydrological connectivity and the dynamic relationship between the river and the lake. The water exchange is crucial for lake level variation, downstream river discharge and the ecosystem. To figure out the water exchange between the Yangtze River and Poyang Lake, a data‐driven model was established based on the support vector regression and genetic algorithm technique. Nine scenarios were set with different river–lake hydrological conditions, divided into two categories: single‐element change scenarios, where only the river conditions or only the lake conditions changed, and combined scenarios, where both elements changed simultaneously. The model could accurately simulate the river–lake water exchange variations. Scenario simulation results show that increasing the river flow or lowering the lake level could cause a decrease in the lake outflow. Conversely, decreasing river flow or raising the lake level could cause an increase in lake outflow. Changing lake conditions have a stronger impact on the water exchange variation than changing river conditions if the change percentages of the situation indicator values are the same. Similarly, lake level increase has a stronger impact on the water exchange variation than lake level decrease. The combined scenarios indicate the additive effect of the corresponding single‐element change scenarios, with a clear linear relationship between their lake outflow changes. This study provides an efficient model for simulating complex hydrological flow relationships in river–lake systems, and supports the management of the Yangtze River and Poyang Lake by providing the characteristics and causes of the river–lake water exchange.
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In 2009, the University of Alabama-Huntsville configured their GOES satellited-based solar radiation product to include Puerto Rico, the US Virgin Islands (USVI), Dominican Republic, Haiti, Jamaica, and Cuba. The half-hourly and daily integrated data are available at 1 km resolution for Puerto Rico and the USVI and 2 km for Hispaniola, Jamaica, and Cuba. These data made it possible to implement estimates of satellite radiation-based evapotranspiration methods on all of the islands. The use of the solar radiation data in combination with estimates of other climate parameters facilitated the development of a water and energy balance algorithm for Puerto Rico. The purpose of this paper is to describe the theoretical background and technical approach for estimating the components of the daily water and energy balance. The operational water and energy balance model is the first of its kind in Puerto Rico. Model validation results are presented for reference and actual evapotranspiration, soil moisture, and streamflow. Mean errors for all analyses were less than 7%. The water and energy balance model results can benefit such diverse fields as agriculture, ecology, coastal water management, human health, renewable energy development, water resources, drought monitoring, and disaster and emergency management. This research represents a preliminary step in developing a suite of gridded hydro-climate products for the Caribbean Region.
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In this study, a particle tracking model was used to simulate the Cu footprints in Poyang Lake under the dual action of complex wind field and lake flow patterns. When ignoring the wind field, the results showed that gravity flow and top‐lifted flow both drove Cu particles to move from south to north, and the backward flow slowed down the velocity of Cu particles, but did not affect the final trend. When considering the wind field, wind‐driven currents had an effect on the horizontal lake flow patterns. Under the influence of wind‐driven current, the top‐lifted flow was the most vulnerable, the backward flow ranks the second, and the gravity flow ranks the third. The results demonstrated the importance of the effect of wind on lake circulation and mixing. Better knowledge of heavy metal footprints in large river‐connected lake was provided to guide future water management.
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The hydrodynamics inside a lake suffers great shifts due to the combined impacts of climate change and anthropogenic activities, which in turn influences the water environment in the lake. Distinguish the impacts of climate change and anthropogenic activities on water age, which indicates the flow patterns and water exchange rates, is of great significance to watershed management. This study performs a quantitative attribution analysis by coupling the environmental fluid dynamics code(EFDC) and the LSTM model. Results showed that the model used in this study can accurately simulate the water level and runoff dynamics, with the Nash-Sutcliffe Efficiency over 0.96 and 0.90, respectively. (2) There exits great spatial heterogeneity of the water age, with average water age of 228.01 and 24.21 days in the floodplains and main channel, respectively. (3) The water age decreased about 30 days for over 2054 km² due to climate change, whereas anthropogenic activities increase the water age in 58% lake area in the dry period and shorten the water age in 82% lake area in the flood period. The results can provide scientific basis and theoretical guidance for water resources management in Lake Poyang Basin.
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A floodplain lake system can be described as a water conveyance-type lake system that is subject to high water-level fluctuations (WLFs). This study investigated the effects of WLF on the nutrient status and the gross primary productivity (GPP) of phytoplankton in Lake Poyang, a large floodplain-lake system in China. This study hypothesized that WLF is the key controlling regulator of the lake’s nutrient status, phytoplankton growth and GPP, driven by its influence on the lake’s hydrological connectivity in combination with water-flow velocity as well as other environmental parameters. The results showed that the intra-annual water levels in this lake varied from 7.61 m to 20.82 m while inter-annual water levels significantly decreased throughout 1989–2018 (P<0.05). Except for pH, most environmental variables and nutrients differed significantly each season. Mean GPP and chlorophyll a (Chl a) concentration during the water rising period was clearly higher compared to the dry season, wet season and falling period. Moreover, nutrient concentration was the main determining factor of phytoplankton growth and GPP during different periods, while water temperature (WT) also played a key role in influencing phytoplankton biomass and GPP during the water rising period. There was also a direct correlation between WLF and GPP during the water rising period, and WLF significantly affected nutrient concentration, subsequently impacting GPP. This study can benefit our overall knowledge of hydrological and ecological dynamics in floodplain-lake systems, while providing an important reference for policymakers in the management of dams and water quality in floodplain-lake systems globally.
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Real-time coupling of a hydro-environmental model and an optimization model is difficult because hydrodynamic model (HDM) and scalar transport model (STM) are both time-consuming, especially when the computational domain is large (e.g., river-lake system). This study presents a new 1D hydro-environmental model for free-surface flows and scalar transport in large river-lake systems. Using a prediction–correction method, hydrodynamic is simulated by solving local linear systems based on domain decomposition. A flux-form Eulerian-Lagrangian method (ELM) is constructed to solve advective transport of scalars in 1D grid systems, and a nested technique is proposed to reduce its startup cost. The resulting STM and HDM both allow large time steps for which the Courant–Friedrichs–Lewy number (CFL) is greater than 1, and they are parallelized using the open multiprocessing technique (OpenMP). Moreover, the STM is good at solving multiscalar transport and has low startup cost. The new model is tested using the Jing-Dongting (JDT) system which is covered by a grid of 2382 cells (with 113,600 sub-grids). Stable and accurate simulations are achieved at large time steps for which the CFL can be larger than 5. A sequential run of the new model runs tens of times faster than that of a conventional 1D model such as the Mike11. Moreover, the efficiency of the new model can be further improved by the OpenMP parallel technique. In the test of scale property of the HDM + STM model (using 32 kinds of scalars and 16 cores), a parallel run is 11.8 times faster than a sequential run, and it only takes the new model 33.3 s to complete a simulation of a 1-year process of unsteady flow and scalar transport in the JDT system.
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This article presents the results obtained from the application of a recently developed coastal area morphological model to simulate the morphological response of a sandy spit/platform system to meteorological forcing of variable intensity. The morphological model applies an unstructured flexible mesh to resolve the bathymetry and allows fully dynamic coupling of and feedback between the modules used to simulate waves, water levels and fluxes, and sediment transport and bed level changes. Morphological changes predicted by the model are compared to available field measurements.
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Poyang Lake is a seasonal lake, exchanging water with the lower branch of the Yangtze River. During the spring and summer flooding season it inundates a large area while in the winter it shrinks considerably, creating a large tract of marshland for wild migratory birds. A better knowledge of the water coverage duration and the beginning and ending dates for the vast range of marshlands surrounding the lake is important for the measurement, modelling and management of marshland ecosystems. In addition, the abundance of a special type of snail (Oncomelania hupensis), the intermediate host of parasite schistosome (Schistosoma japonicum) in this region, is also heavily dependent on the water coverage information. However, there is no accurate digital elevation model (DEM) for the lake bottom and the inundated marshland, nor is there sufficient water level information over this area. In this study, we assess the feasibility of the use of multitemporal Landsat images for mapping the spatial‐temporal change of Poyang Lake water body and the temporal process of water inundation of marshlands. Eight cloud‐free Landsat Thematic Mapper images taken during a period of one year were used in this study. We used the normalized difference water index (NDWI) and the modified normalized difference water index (MNDWI) methods to map water bodies. We then examined the annual spatial‐temporal change of the Poyang Lake water body. Finally we attempted to obtain the duration of water inundation of marshlands based on the temporal sequence of water extent determined from the Landsat images. The results showed that although the images can be used to capture the snapshots of water coverage in this area, they are insufficient to provide accurate estimation of the spatial‐temporal process of water inundation over the marshlands through linear interpolation.
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Estimation of specific yield (Sy) of an aquifer is of great importance in water resource management. In this study, an experimental drainage method was developed to determine specific yield of an alluvial aquifer of the Platte River valley, Nebraska, USA. Sets of sediment cores with continuous interval depth were collected to plastic tubes using the direct push technique and then taken to the laboratory. During the Sy experiment, those sediment cores were re-saturated by placing them vertically in a large water tank. Sy was determined by the water drained from the sediments by force of gravity in a bracket. Our results show that the values of Sy varied largely with depth at each site and the variability for Sy with interval depth between the test sites is also observed. This spatial heterogeneity in Sy might result from the variation of grain size, grain shape, sorting and compaction of sediments in different cores with interval depth. The Sy for all sediment cores ranged from 0.01 to 0.18 and the mean value was 0.08±0.04. Our drainage method can functionally preserve the sedimentary structures in their original state and it is easier to experiment at a lower expense.
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Multi-temporal satellite images are widely used to delineate objects of interest for monitoring surface changes. Threshold value(s) are often determined from a histogram of a delineation index. However, the threshold determined may vary and be case-dependent, with images taken at different times. Although the variation is well known, its cause remains unclear, and this raises doubts about the reliability of the classification results. This study selects three widely used indices, the near-infrared (NIR) band, the normalized difference vegetation index (NDVI) and the normalized difference water index (NDWI), all of which can be used to delineate water surfaces. Our theoretical analysis reveals that sensor calibration, the Sun–target–satellite geometry and the atmospheric optical properties create synthetic effects on the satellite's digital number (DN) and, subsequently, on the thresholds for delineation. The DN-based threshold has a significant dependence on the reflectance-based counterpart, which has been proved with multi-temporal Moderate Resolution Imaging Spectroradiometer (MODIS) data for the Poyang Lake region of China. Our results show that a DN-based threshold is generally higher than a reflectance-based one, and ∼90% of the difference is accounted for by temporal influences. A quantification of the temporal influences provides a physical explanation to the variation in thresholds, and the findings should be valuable for improving the reliability of long-term studies using multi-temporal images.
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The Three-Georges Dam holds many records in the history of engineering. While the dam has produced benefits in terms of flood control, hydropower generation and increased navigation capacity of the Yangtze River, serious questions have been raised concerning its impact on both upstream and downstream ecosystems. It has been suggested that the dam operation intensifies the extremes of wet and dry conditions in the downstream Poyang Lake, and affects adversely important local wetlands. A floodgate has been proposed to maintain the lake water level by controlling the flow between the Poyang Lake and Yangtze River. Using extensive hydrological data and generalized linear statistical models, we demonstrated that the dam operation induces major changes in the downstream river discharge near the dam, including an average “water loss”. The analysis also revealed considerable effects on the Poyang Lake water level, particularly a reduced level over the dry period from late summer to autumn. However, the dam impact needs to be further assessed based on long-term monitoring of the lake ecosystem, covering a wide range of parameters related to hydrological and hydraulic characteristics of the lake, water quality, geomorphological characteristics, aquatic biota and their habitat, wetland vegetation and associated fauna.
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We present a multi-year climatology of cloud-base-height (CBH), cloud-top-height (CTH), and trade wind inversion base height (TWIBH) for the Hawaiian region (18°N–22.5°N, 153.7°W–160.7°W). The new climatology is based on data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO), the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), ceilometer observations and radiosondes. The climatology reported here is well suited to evaluate climate model simulations and can serve as a reference state for studies of the impact of climate change on Hawaiian ecosystems. The averaged CBH from CALIPSO in the Hawaiian Region is 890 m. The mean CTH from CALIPSO is 2110 m, which is close to the mean TWIBH from COSMIC. For non-precipitating cases, the mean TWIBH at both Lihue and Hilo is close to 2000 m. For precipitating cases, the mean TWIBH is 2450 m and 2280 m at Hilo and Lihue, respectively. The potential cloud thickness (PCT) is defined as the difference between TWIBH and CBH and the mean PCT is several hundred meters thicker for precipitating than for the non-precipitating cases at both stations. We find that the PCT is more strongly correlated to the TWIBH than the CBH and that precipitation is unlikely to occur if the TWIBH is below 1500 m. The observed rainfall intensity is correlated to the PCT, i.e., thicker clouds are more likely to produce heavy rain.
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An automated base flow separation technique has been developed and tested. Base flow is considered to be the ground-water contribution to stream flow. Estimates of the amount of base flow can be derived from stream flow records. Such estimates are critical in the assessment of low flow characteristics of streams for use in water supply, water management, and pollution assessment. An automated base flow separation technique using a digital filter has been tested against three other automated techniques and manual separation methods. The filter appears to be comparable to other automated techniques in its ability to reproduce the results produced from graphical separation techiques. The filter technique is easy to use and has the added advantage in that it can be adjusted by the user to take into account personnel preferences in separation of stream flow into surface flow and base flow.The slope of the base flow recession has been used to estimate the volume of water in storage in the basin above the level of the stream channel, the amount of recharge to the shallow aquifer, and as an input into water budget models. A second automated technique was developed to calculate the slope of the base flow recession curve from stream flow record. This technique is an adaptation of the Master Recession Curve procedure. The results of this method were compared to manual estimates with an efficiency of 74 percent.
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Poyang Lake in Jiangxi Province is the largest freshwater lake in China and is historically a region of significant floods. Annual events of peak lake stage and of severe floods have increased dramatically during the past few decades. This trend is related primarily to levee construction at the periphery of the lake and along the middle of the Changjiang (Yangtze River), which protects a large rural population. These levees reduce the area formerly available for floodwater storage resulting in higher lake stages during the summer flood season and catastrophic levee failures. The most severe floods in the Poyang Lake since 1950, and ranked in descending order of severity, occurred in 1998, 1995, 1954, 1983, 1992, 1973, and 1977. All of these floods occurred during or immediately following El Niño events, which are directly linked to rainfall in central China. The 2-year recurrence interval for maximum annual lake stage during El Niño years is 1.2 m higher than during non-El Niño years. The 10-year recurrence interval is 1.4 m higher during El Niño years than during non-El Niño years. Copyright © 2006 Royal Meteorological Society.
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In the middle reaches of the Yangtze River, the floods have become more and more frequent, and the water level rises higher than before. The damages are becoming ever more serious. This is primarily a consequence of human activity in the river basin. Three aspects deserve particular attention. First, destruction of vegetation has led to soil erosion in the upper reaches. In the past 30 years, the forest cover has been reduced to half, while the area exposed to severe erosion doubled in size. In the long run, this can be expected to increase flooding. Second, land reclamation and siltation has reduced lake sizes. This has resulted in decrease of the flood storage capacity. Third, the construction of levees has caused flood levels to rise due to restricted flood discharge capacity. Establishment of the Great Jinjiang levee caused silting up of the riverbed and valley in the mid-reaches of Yangtze. Consequently, the discharge capacity decreased to 60,000–68,000 m3/s, which is sufficient only for ordinary floods. This article concludes that the deteriorating flood situation is the result of inappropriate human intervention in the natural environment. It is suggested that the appropriate strategy should change from “keeping the flood away” to “giving the flood way”. Related tactics and strategies under consideration are briefly summarized.
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Lake eutrophication leading to water pollution is a major global concern. In recent years, rapid economic growth and the increase in the intensity of resource exploitation in China have caused the influx of nitrogen and phosphorus into lakes. This in turn has led to more severe lake eutrophication, more frequent outbreaks of algal blooms, and the degradation of lake ecosystems. An effective plan balancing economic growth with the reduction of nitrogen and phosphorus emissions is greatly needed. The design and implementation of such a plan requires the collection and analysis of pertinent data. In this paper, we use the environmental computable general equilibrium (ECGE) model to identify the most effective way to balance economic growth with the reduction of nitrogen and phosphorus emissions. For the multiregional analysis, we use social accounting matrices (SAMs) and a provincial trade matrix based on the assumptions of the gravity model. We consider the Poyang Lake Watershed as a case study to illustrate the utility of the model. Based on present conditions in the Poyang Lake Watershed, restricting nitrogen and phosphorus emissions from sectors with the highest emissions is more effective for balancing economic growth and the reduction of nitrogen and phosphorus emissions than restricting nitrogen and phosphorus emissions from all sectors.
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Summary Recently available hydrological data from Hukou station at the junction of the Poyang Lake with the Yangtze River along with other data from stations in the Poyang Lake basin have allowed further examination and understanding of the basin effect (basin dis- charge generated by rainfall) and the Yangtze River blocking effect on variations of the Poyang Lake level and floods at annual to decadal scales. Major results show that the basin effect has played a primary role influencing the level of Poyang Lake and development of severe floods, while the Yangtze River played a complementary role of blocking outflows from the lake. In most cases, only when the basin effect weakened did the river effect become large, a relationship indicating that the river's blocking effect diminishes when the lake level is high from receiving large amount of basin discharge, albeit a few excep- tions to this relationship occurred when river flow also was elevated from receiving large rainfall discharges in upstream areas. Moreover, the basin effect has become stronger in the period 1960-2003 in accordance with the increase of warm season rainfall in the Poy- ang Lake basin. In particular, large increases of the basin's rainfall in the 1990s corre- sponded to the most severe floods (in 1998, 1995, and 1992) of the last 4 decades. The strong increase of warm season rainfall in the Poyang Lake basin in the 1990s is consistent with the recent southward shift of major warm season rain bands in eastern China. Results of this study provide a utility for improving predictions of the Poyang Lake level and floods, which affect a population of about 10 million. ª 2007 Elsevier B.V. All rights reserved.
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Highlights ► We evaluated the applicability of TRMM satellite rainfall at different time scales. ► TRMM is better at determining rain occurrence and mean value than rainfall extreme. ► TRMM satellite data is not suitable to drive hydrological model at daily scale. ► TRMM satellite data is useful input to hydrological model at monthly scale. ► Different rainfall data can change the proportion of water balance components.