鄱阳湖水位变化的复合驱动机制

基于对鄱阳湖开放水文系统特点和影响因素的深入分析，通过构建一组联合的神经网络模型，定量辨识了包括湖盆地形变化、三峡工程作用、长江流域气候变化等因素对湖泊水位变化的影响分量、时空差异及其发展趋势，并对其作用机制进行了探讨。结果表明：相对于1980—1999年，2003—2014年鄱阳湖湖盆地形变化、三峡工程运行、长江流域气候变化和其他人类活动对湖泊水位降低的平均贡献率分别为50%、18%和32%。由于影响机制的不同，湖泊水位对这3个驱动因子的响应表现出明显的时空差异。冬、春季节湖泊水位降低主要由湖盆地形变化引起，而夏、秋季节的水位降低则主要归因于长江流域气候变化及其他人类活动的综合影响。湖盆地形变化对湖泊水位的影响在湖区都昌站附近最为突出，并且该影响仍呈长期增加趋势。三峡工程引起的湖泊水位变化在湖口处最大，向南部湖区逐渐减弱，其长期变化趋势日渐稳定。长江流域气候变化及其他人类活动的作用值得特别注意，该影响年际间波动较大，在某些年份里（如2006年、2011年）可成为湖泊水位降低的主导因素，但年际变化趋势不明显。

Compound Driving Mechanism of Water Level Change in the Poyang Lake

Since the beginning of the 21st century, the Poyang Lake has undergone significant hydrological change. However, so far, the complex driving mechanism behind is still not clear. Based on the in-depth analysis of the characteristics and influencing factors of the open hydrological system of Poyang Lake, two combined neural network models were constructed to quantitatively distinguish the impacts, spatial-temporal differences and development trends of compounding influencing factors to this hydrological change, such as lake bottom topography change, the operation of the Three Gorges Dam (TGD), and climate change and other human activities over the Yangtze River basin. The driving mechanism of the influencing factors were then explored. Results indicate that with reference to the period 1980-1999, the average contributions of lake bottom topography change, the operation of the TGD, climate change and other human activities over the Yangtze River basin were 50%, 18% and 32% respectively to lake decline during 2003-2014. The response of the lake water level to the three driving factors shows obvious spatiotemporal differences due to different influencing mechanisms. The decline of lake water level in winter and spring is mainly caused by the change of lake basin topography, while the decline of water level in summer and autumn is mainly due to the comprehensive influence of climate change and other human activities in the Yangtze River Basin. The influence of lake bottom topography change on the decline of lake water level is the most prominent near Duchang, and the effect is still increasing. The decline of lake water level caused by the TGD is the largest at Hukou and gradually weakens to the south of the lake, while this is becoming more and more stable. The role of climate change and other human activities in the Yangtze River Basin deserves special attention. The inter-annual fluctuation of this effect is large. In some years (such as 2006, 2011), it can be the dominant driving factor of lake water level decline. However, the long-term trend of this effect is not obvious.