联合GRACE重力卫星和水文模型的黄河流域水文干旱及其生态效应研究

Drought disasters in China, with a wide range, high frequency, long time, resulting in serious losses on the water security, have a great damage on ecological environment, food security and social stability. The drought is more complex under the influence of climate change and human high-intensity activities. It is difficult to fully reflect the drought characteristics using the traditional drought monitoring indicators which are based on one or some single hydrological variables. This project focuses on the critical scientific issues of accurate assessment of hydrological drought and the response of the ecological environment to drought. The Yellow River Basin, which is affected by the global climate change and intensive population activities, is selected as the research object. Combining GRACE gravity satellites and VIC hydrological model, the long-term water storage changes data are reconstructed. The integrated drought assessment indicators, which consider the changes of groundwater, soil water, surface water, precipitation and other hydrological variables are obtained and used to distinguish the hydrological drought characteristics in the Yellow River Basin. The relationships between ENSO, gross national product etc. and drought were analyzed. The project also discusses the spatial-temporal change characteristics of hydrology elements during drought and the response and resilience of different surface ecological environment to drought event. The research results will provide theoretical and information support for hydrology and water resources management, ecological and environmental protection, drought prevention and resistance measures in the Yellow River Basin.

干旱灾害在我国发生范围广、频率高、时间长、造成的损失严重，对水资源安全、生态环境、粮食安全以及社会稳定产生了极大的损害。气候变化和人类高强度活动双重因素影响下的旱灾发展过程更加复杂，传统的干旱监测指标多以单一或一些水文要素变量为依据，难以全面反映干旱特征。本项目围绕“水文干旱精确评估及生态环境对干旱的响应”这一关键科学问题，选择受全球气候变化影响显著且人口活动密集的典型地区黄河流域为研究对象，联合GRACE重力卫星和VIC水文模型重构长时序水储量变化数据，计算考虑地下水、土壤水、地表水、降水等水文变量动态变化的集成干旱评估指标，分析黄河流域水文干旱特征及其与ENSO、国民生产总值等的关系；探讨旱灾期间水文要素时空动态变化规律以及不同地表生态环境对干旱的响应及恢复力。本项目研究成果可以为黄河流域水文水资源管理、生态环境保护、防旱抗旱措施的制定等提供理论和信息支撑。

黄河流域在我国经济社会发展和生态安全方面具有十分重要的地位，是我国重要的经济地带；又是连接青藏高原、黄土高原、华北平原的生态廊道。流域水旱灾害多发、频发，给该流域造成了严重的人员伤亡和财产损失，已成为影响生态环境的重大灾害。在气候变暖和人类活动双重影响下，黄河流域水资源的供需矛盾更加突出，社会正常生产、生活对水的依赖性日益增加，一旦遭遇重大旱灾，将引发一系列的资源、环境与生态问题。本项目联合GRACE实测水储量变化量、气象资料、遥感数据，及水文/陆表过程模型资料，采用机器学习算法（人工神经网络、多元线性回归分析等）重构1981—2016年间黄河流域高精度时空水储量数据资料；基于重构长时序高精度水储量变化量数据资料反演集成干旱评估指标；对比分析集成干旱评估指标与传统干旱评估指标（例如SPI，SPEI，sc_PDSI），明确黄河流域多类型干旱灾害时空分布特征及规律；探讨分析NDVI、LAI，气象、水文等要素时空演变规律，着重探讨分析生态水文要素对干旱灾害的响应。本项目得到的主要研究成果包括：1.基于ANN机器学习算法，联合WaterGAP水文模型模拟的流域土壤水、地下水、蒸散发等变量，及降水、气温数据，可以获取高精度时序和格网TWS数据资料。2.黄河流域水资源在1981-1999年间平稳或缓慢减少，2000-2004阶段快速上升，2005-2017快速下降。多类型干旱指标探讨分析发现黄河流域秋季干旱环境呈加剧趋势，其中20世纪90年代-21世纪初期干旱发生频繁；空间上干旱化趋势集中分布在流域中游。3.黄河流域气候要素降水、气温、蒸散发量在研究时段内均呈增多趋势。流域草地和林地面积增加，耕地面积减少；植被覆盖指数NDVI以0.0011/yr的速率增加，叶面积指数LAI也呈显著增加趋势。而旱灾对不同生态系统产生不同程度的负效应，对林地NDVI影响最大，耕地NDVI影响最小。基于对长时间序列水储量，多类型干旱指标，和生态水文变量关联分析，实现了黄河流域水-植被-灾害相互作用分析，为黄河流域资源环境保护提供科学依据。

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