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During the past few decades, the ecosystems of lakes have been reshaped greatly by global climate change and expanding human activities. As the second largest freshwater lake in China, Dongting Lake is the most important regulating lake in the Yangtze River Basin because it has extensive flood storage capacity. The dynamic characteristics of its circulation and sediment transport are significantly affected by the scheduling and interception of control reservoirs at the upper reaches of the Yangtze River. In this paper, a central lake reservoir is proposed to improve the flood and drought resistance of Dongting Lake. The efficiency of the central lake reservoir is investigated numerically by developing a two-dimensional shallow water model. We demonstrate that current velocity and water elevation during flood and drought events can be influenced significantly by the construction of the central lake reservoir. The flood storage capacity of the central lake reservoir can reduce the peak flood elevation significantly in West Dongting Lake, which would enhance its flood resistance. The water replenishment of the central lake reservoir in the dry season can also efficiently increase the lake water elevation to enhance the drought resistance in the area surrounding the lake. Our findings have important implications for policy makers and their management of Dongting Lake. [ABSTRACT FROM AUTHOR]

The operation of the Three Gorges Reservoir (TGR) affects the evolution of the interactions between the Yangtze River and Dongting Lake in China and water diversions from the river, which are essential to water resources management in this large river–lake system. Due to the lack of up-to-date and detailed channel topographic/bathymetric data, a simplified flow model based on rating curves was developed to simulate discharges in the river system, and to further quantify and differentiate the contributions of river erosion and flow regulation of the TGR at a seasonal scale. The results indicate that the effect of channel alteration counteracts the effect of reservoir regulation in the high-flow periods. The impacts of TGR regulation on water diversions for both pre- and post-flood seasons were significant, but no obvious changes in the discharge diversion ratios were observed on an annual time scale. [ABSTRACT FROM AUTHOR]

Abstract: Water‐level variations are an internal aspect of lake ecosystems that play a key role in structuring aquatic diversity and providing ecosystem services. In this study, the hydrologic alteration of Dongting Lake induced by the Three Gorges Dam (TGD) was assessed using indicators of hydrologic alteration and range of variability approach. The results demonstrate a declining trend in autumn water level (0.52–2.26 m) and 5–35 days' advancement for date of minimum annual water level because of the impound of water by the TGD in early autumn. The spatial patterns in the degree of the indicators of hydrologic alteration were different among the sub‐lake regions. Annual minimum water level and timing of annual extreme water level suffered a high degree of alteration in the eastern part of the lake, whereas autumn water level, date of minimum water level, and number of reversals in the western part of the lake showed a high degree of alteration. The average integrated degree of hydrologic alteration (D0) for Dongting Lake was 50.40%, indicating that the hydrologic regime suffered a moderate alteration. The most ecologically relevant hydrologic indicators are critical for understanding eco‐hydrology. On the basis of principal component analysis, the five selected ecologically relevant hydrologic indicators were 90‐day minimum, date of minimum, high pulse duration, date of maximum, and May water level. Further studies are required to understand the impact of the TGD on water conditions in Dongting Lake, especially related to the response of the aquatic ecosystem. [ABSTRACT FROM AUTHOR]