通江湖泊干旱的多成因机制研究

Yangtze-connected lakes generally have complicated intra- and inter-annual variations, experiencing remarkable changes. The frequently occurred severe lake droughts in the mid-lower reaches of the Yangtze River is of great concern to China and the world. It remains unclear what is responsible for the anomaly phenomenon. The proposed proposal is to investigate the drought issue, with focuses on the Poyang Lake region. First, it will construct comprehensive data sets of lake water storage, terrestrial evapotranspiration, soil moisture, and other hydrological components contributing to the lake water change. The data come from multiple sources including hydrological and meteorological stations, field surveys, in-situ observation and satellite remote sensing. Lake topography, lake water storage, terrestrial evapotranspiration and soil moisture will be produced with advanced retrieval approaches from the multi-source satellite data. Error analysis will be also made to secure the data sets with a high accuracy. Second, water balance analysis and multivariate analysis will be used to find lake water variability and its synthetic responses to each hydrological component within the Poyang Lake Basin. A hydrodynamic model will be incorporated to quantify the lake water loss due to variation of mainstream flow of the Yangtze River. Third, topographic analysis, trajectory analysis and hydrodynamic simulation will be performed to evaluate anthropogenic influences on lake water alternation. The influences include land cover change, water impoundments of the Three Gorges Dam, and change of lake capacity due to land reclamation, dike and sand excavation. Fourth, from a new perspective lake droughts will be addressed and its spatio-temporal connection through water deficits across meteorological, soil moisture, streamflow droughts. Upon the insightful investigation into the mechanisms of lake water variation, the study will further clarify the multi-causality of recent severe lake droughts and especially identify the contributions from anthropogenic influences. Strategies will be proposed for adaptation to the lake droughts. This study should benefit development of quantitative remote sensing and its application in hydrology and enrich lake hydrology. It will offer a scientific basis for sustainable development of eco-economic zone and water-use safety over the region in practice.

通江湖泊水量变化复杂，影响因素多样。本世纪以来长江中下游湖区极端干旱事件多发，世人瞩目。本项目以鄱阳湖区为核心研究区域，综合定位监测、野外考察、长期水文气象观测和多源遥感数据，采用非参数化蒸散计算方法、尺度转换与误差评估等多种新颖方法，构建湖泊水量、流域蒸散和土壤水分等新的长时序数据。结合多尺度水量平衡分析、变化轨迹法和水动力模拟等先进方法，系统分析湖泊水量变化规律及流域水文要素变化过程，阐述湖区下垫面变迁、流域地表要素演变和出湖边界条件变动的多重水文效应，定量辨析气候变化与人类活动作用。以水分亏缺为分析主线，从崭新的研究视角，解析湖泊干旱与气象干旱、土壤干旱、径流干旱之间的时空传承过程，阐明湖泊干旱的多成因机制，尤其是人类活动的贡献。在定量遥感方法和湖泊干旱研究上实现创新，推动水文学与定量遥感的交叉融合，深化湖泊水文学，为生态经济区建设和流域用水安全保障等提供科学依据与合理建议。

通江湖泊水量变化复杂，影响因素多样。本世纪以来长江中下游湖区极端干旱事件多发，世人瞩目。本项目以鄱阳湖水量为核心研究对象，以鄱阳湖区下垫面为基本条件，以流域水文要素变化为背景条件，以长江干流水情变动为边界条件，抓住三个关键科学问题（入湖径流的主控因素、出湖边界的控制作用、湖泊干旱的复合成因），结合野外高频监测、遥感反演和模型分析，突破三个研究难点（地表蒸散估算、湖区产流补给作用、气候变化与人类活动影响区分）；在建立流域水文要素长时序数据集的基础上，从湖体-湖区-流域三个层面，解析了近六十年来鄱阳湖流域水量收支要素的时空变化规律；从气象干旱演变入手，结合流域水量收支的多尺度平衡原理，揭示了本世纪以来鄱阳湖干旱频发的自然变率和人类活动复合成因。研究表明，本世纪以来湖泊干旱事件的强度明显增强，极端干旱事件明显增加。从总体上看，入湖流量减少是最主要的原因，其次是出湖流量增加和湖区降水减少，湖区蒸散增加的贡献较小。其中，入湖流量的减少归因于流域气象干旱、蒸散增加以及流域内水库调蓄等人类活动作用，出湖流量的增加则归结于长江对鄱阳湖的顶托作用减弱。气象干旱不但具有基本的空间模态，且会进行空间迁移，并与大尺度的气候变化之间存在着统计关联。长江上游三峡水库的秋季蓄水会减弱长江顶托作用，进而增加同期鄱阳湖干旱的严重强度，但尚无证据表明它可单独触发干旱事件。本项目较为全面地回答了本世纪来鄱阳湖干旱频发的复杂成因，研究结果对于评估鄱阳湖区水量安全、应对湖区极端干旱事件、提升三峡水库生态调度质量以及全流域水资源高效利用等提供了科学的依据。