Impact of climate change and human activities on the changes of ecological flow indicators in the Lake Poyang Basin since 1960s

基于鄱阳湖流域五河水文站1960-2013年逐日径流量和14个国家级气象站的日气象数据，本文利用长短记忆模型框架构建神经网络模型来开展鄱阳湖流域的径流过程模拟，结合生态赤字与生态盈余等生态径流指标，定量分析了鄱阳湖流域的水文变异特征.同时，利用差异化的情景模拟方式，定量区分了人类活动和气候变化对鄱阳湖流域生态径流变化的贡献分量.研究结果表明：（1）5个站点的夏季径流贡献率达到40%以上，年内的生态盈余主要发生在夏季，基准期的夏季径流贡献率大于实测期和模拟期，可能的原因是水利工程的蓄水调水在时间上分摊了夏季的径流压力.（2）生态径流指数与降水在年尺度上有较好的一致性，相关系数均在0.7以上，但各生态流量指标与春、秋、冬季降水的一致性较差，相关系数均小于0.6，降水最多的夏季与年际变化最相似.（3）年内变化上，气候变化引起生态赤字的减少，春、冬季节减少最为强烈；人类活动引起生态赤字的增加，在秋、冬季节增加最多，而在冬季引起生态盈余的减少.（4）年际上，生态盈余的变化中，除了赣江以外（气候变化的影响贡献为26%），其他河流中气候因素是影响生态盈余的主要原因（60%~85%），对生态赤字而言，除了饶河（25%）和抚河（52%），赣江、信江和修水气候因素的影响贡献都达到了95%以上.研究结果为更好地了解气候变化与人类活动对流域水文变化的影响提供了一种新的研究方法，为鄱阳湖流域水资源管理提供了理论支持.;Based on the daily runoff data of the hydrological station in the Lake Poyang Basin (from 1960 to 2013) and the daily meteorological data of 14 national meteorological stations, this paper applied the long-short-term Memory network (LSTM) to simulate the runoff dynamics in the basin and attribute the contributions of human activities and climate change on eco-flow variations using eco-flow indices. The results show that:(1) The contribution rate of summer runoff in the five stations reached more than 40%, and the ecological surplus was mainly in summer. The contribution rate of summer runoff in S0 was higher than that in S1 and S2, which may be due to the water storage project. (2) Annually, the changes in the eco-flow indices and precipitation are relatively consistent in the entire period (with correlation coefficients above 0.7), however, the correlation between the eco-flow indices and precipitation is lower at the seasonal scale. (3) Inter-annually, climate change dominant the variation of ecological surplus (60%-85%) in the basin except for the Ganjiang River (26%). Except for the Raohe River (25%) and Fuhe River (52%), the contribution of climate change on the variations of eco-flow indices are 25% in Raohe River, 52% in Fuhe River, 95% in Ganjiang River, 98% in Xinjiang River, and 99% in Xiushui River, respectively. (4) At seasonal scale, climate change causes the reduction of eco-deficit and the reduction is strongest in spring and winter. Whereas the eco-surplus increased in most cases. Human activities cause the increase of eco-deficit, mostly in autumn and winter, and it causes a decrease in eco-surplus in winter. Our research proposed a new method for attributing the impact of climate change and human activities on hydrological changes. The results should provide theoretical support for water resources management in the Lake Poyang Basin.