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As a large open lake that connects to the lower Yangtze River, the Poyang Lake, China, has persisted dramatic water level decline since 2003. For better management of lake water resources and ecosystem, this study quantitatively examined the contributions and spatiotemporal differences of compounding influencing factors to this hydrological change. Attempts were achieved through the reconstruction of lake water level series by two combined neural network models. The results indicate that with reference to the period 1980–1999, the average contributions to lake decline during 2003–2014 of lake-bottom topography change, the operation of the Three Gorges Dam (TGD), and climate change and other human activities over the Yangtze River basin were 50%, 18%, and 32%, respectively. The response of the lake water level to the three factors shows obvious spatiotemporal differences due to different influencing mechanisms. It is worth noting that the effect of lake-bottom topography change is still increasing across the lake. In addition, the reduction of precipitation in the Yangtze River basin should be highly correlated to the water level decline of the lake. From the perspective of maintaining a certain water level of the lake and preventing continuous decline and shrinkage, constructing the proposed water control structure would be an effective solution. [ABSTRACT FROM AUTHOR]

Hydropower operating rules can guide reservoir release and storage for maximizing hydropower generation. The optimal hydropower operating rules are usually derived by numerical hydropower simulation methods. This study focuses on the analytical solution to optimal hydropower rules for storage allocation of a multireservoir system. An energy function, the E -function, is proposed to describe the objective of hydropower generation. The E -function for a multireservoir system can be represented as a function of two variables: the proportional coefficient (alpha, which represents the proportional relationship between any two reservoirs in a multireservoir system) and the total increment in storage. The alpha discriminant deduced from the E -function is used to infer the optimal reservoir storage allocation for maximum hydropower generation. With the Ankang-Danjiangkou reservoirs as a case study, the E -function and the alpha discriminant were compared with the numerical hydropower simulation. The results indicated that (1) the E -function can be used to estimate the hydropower generation for multireservoir systems with acceptable hydropower generation estimation errors between the analytical E -function and the numerical hydropower simulation; and (2) the optimal reservoir storage allocation can be explicitly obtained using the alpha discriminant. These findings are helpful for understanding the allocation of reservoir storages in multireservoir systems. [ABSTRACT FROM AUTHOR]

Affected by intensive human activities, basin hydrologic systems show characteristics of a dualistic structure. Thus, simulation of hydrological processes needs to consider the social water cycle system to obtain a more accurate result. This study uses a dualistic water cycle simulation system to simulate the hydrological processes affected by intensive human activities, which comprises the natural water cycle system and social water cycle system. The social water cycle system includes the agricultural water cycle system, industrial water cycle system, domestic water cycle system, and cross-regional allocation system. As part of the dualistic water cycle simulation system, an integrated dualistic hydrological model is developed which couples a distributed hydrological simulation module with a water resource allocation module. The integrated modeling approach is applied to the Haihe River basin. The results show that the model performance can be improved when considering coupled simulation of natural and social water cycle systems. This model can also be used to investigate the evolutionary relationships among the natural and social water cycle systems in the study region, and to assess the regional water resources in other basins affected by intensive human activities. [ABSTRACT FROM AUTHOR]