变化环境下鄱阳湖流域水文响应机制及其影响因素的定量区分研究

Under the background of climate variability and intensive anthropogenic stresses, Poyang Lake and its surrounding catchments have suffered frequent droughts and floods. As an important national development region of "Poyang Lake ecological and economic zone" as well as the area of "Mountain-River-Lake" project in the Jiangxi Province, concerns on the changes of regional climatical, hydrological and ecological processes in the Poyang Lake basin have rised all around the country. We present this research aims to investigate the mechanism of hydrological response in the Poyang Lake basin under the changing environment, and attempt to quantitative distinguish the impacts of climate variability and human activities on the change of watershed streamflow. According to the evaluation of changes of catchment hydro-meteorological characteristics, a coupled water and energy budget analysis is then used to reveal the mechanism of hydrological response in the Poyang Lake basin. The relative effects of climate variability and human activities on the change of streamflow will be distinguished and examined under different spatial and temporal scales. In addition, based on a framework describing the sensitivity of annual streamflow to precipitation and potential evaporation, we decide to establish a water resource evaluation model to quantitatively assess the contribution of climate variability and human activities on the change of mean annual streamflow. This result is further compared and validated from a distributed hydrological simulation in a selected river subbasin, and specific hydrological responses of land use/land cover change is also examined..The outstanding innovation of this project is that we investigate the mechanism of hydrological response in the Poyang Lake basin from a perspective of coupled water and energy budget analysis, and provide an impirical and a quantitative assessments on the effect of climate variability and human activities on the change of streamflow. We believe the result of this research is essential not only for in-depth understanding the eco-hydrological shifts in the lake-catchment system under the impact of nature and human activities, but also for local water resources management as well as floods and droughts protection in the middle and lower reaches of Yangtze River.

鄱阳湖流域是长江中下游水旱灾害的重灾区，作为当前国家和地方正在实施的环鄱阳湖生态经济区建设和"山江湖"综合开发战略的重要区域，鄱阳湖及其流域的气候、水文以及生态过程备受关注。本项研究针对目前鄱阳湖流域水资源变化机制分析和定量研究缺乏这一现状，通过对流域水文-气象要素变化特征的综合分析，从地表水热收支变化的角度，研究不同时期流域水资源变化对气候变化和人类活动的响应过程，揭示变化环境下鄱阳湖流域的水文响应机制。在此基础上，基于一定的水文敏感性分析，建立起流域尺度上的水资源变化评价模型，并结合分布式水文模拟的分析结果，定量化识别近50年来气候变化和人类活动对流域水资源变化的影响分量及其空间差异。研究结果对深入理解和认识湖泊-流域系统对自然和人类活动的响应具有重要意义，并可为流域水旱灾害防治、水资源管理和生态环境治理提供科学依据和对策。

全球变化背景下鄱阳湖流域水旱灾害频繁，是长江中下游游水旱灾害的重灾区和多发区。本项目对鄱阳湖流域气候、水文水资源演变特征及其影响因素开展了深入研究，取得了以下主要研究成果：（1）从流域水热收支变化的角度，采用经验判别和定量区分相结合的方法，研究了鄱阳湖及其主要水系流域尺度上气候变化和人类活动对径流变化的影响分量。结果表明气候变化和人类活动的相对作用在不同时空尺度上存在差异，对整个鄱阳湖平均状况而言，相对于1960s，1970s～2000s等不同年代气候变化因素引起径流增加的分量在75.3～261.7mm之间；人类活动作用起着减小径流的辅助作用，其引起的径流减小分量在5.4～56.3 mm。（2）在年际尺度上，流域参考蒸发量对日照时数变化最为敏感，其次是相对湿度、风速和日平均气温，水汽压的变化对参考蒸发量影响十分微弱。尽管近50年来流域气温上升和相对湿度下降在一定程度上可引起参考蒸发量的增加，但日照时数的缩短和风速的下降在很大程度上抵消了流域气温上升和相对湿度下降对参考蒸发量的影响，并引起流域参考蒸发量的显著下降。进一步研究揭示，蒸发量的变化是众多气候要素综合作用的结果，并且主要气候变量对参考蒸发量的相对贡献在时间上并不是稳定不变的，不同时期波动较大。（3）鄱阳湖流域春、秋季节有干旱化的发展趋势，而冬、夏季节有湿润化的趋势；气温对气候干湿的影响不容忽视，特别是近年来的高温、热浪对气候干旱起着重要的促进作用。在过去50年中，流域湿转旱的发生频率要高于旱转湿。受流域下垫面特性及面积大小的影响，水文干旱一般比气象干旱的出现时间延迟一个月左右。2个月时间尺度的SPEI指数对鄱阳湖流域水文干旱具有较好的预警监测意义。本项目研究结果对深入理解和认识湖泊—流域系统对自然和人类活动的响应具有重要意义，并可为流域水旱灾害防治、水资源管理和生态环境治理提供科学依据和对策。