水文干旱演变归因与定量评价方法研究

Hydrological drought is a key link connecting meteorology drought, agriculture drought and social economy drought. Due to the reduction of surface runoff, the ground water has become the main water sources for many cities in the northern part of China, thus causing serious overexploitation of ground water. Hydrological drought actually reflects integrated changes in surface and ground water resources. However, the quantitative evaluation of traditional hydrological drought only takes surface runoff as the indicator, but neglects the impact of violent changes in ground water. Therefore, it is difficult to comprehensively reflect the real status and evolutionary process of regional hydrological drought. This program selects the northern part of the Haihe River as a typical basin. By adopting such traditional evaluation methods as displacement theory and standard runoff index, taking the distributed hydrological cycle model as a technical platform and ground water index as input information, it aims to study the evaluation methods for hydrological drought to fully reflect the integrated changes of surface water and ground water. It aims to analyze the frequency, intensity, duration and influence scope in order to study the spatial-temporal evolution of hydrological drought under changing conditions, and identify the key driving factors which affect the hydrological drought. By making a quantitative calculation of the contributing rates of such factors as climate change, changes in underlying surface and water exploitation and utilization, it also aims to explore and analyze the evolutionary process and driving mechanism of hydrological drought so as to provide scientific strategy for drought adaption and technical support for water resources management.

水文干旱是联系气象、农业、社会经济干旱的一个关键环节。北方地区由于地表径流衰减，地下水超采严重，其水文干旱状态实质是地表、地下水资源的综合变化的具体表现，传统仅以地表径流为指标的水文干旱评价方法未能考虑地下水剧烈变化对水文干旱的影响，难以全面反映区域水文干旱的真实状态和形成过程。针对上述问题，本项目基于游程理论、标准径流指数等传统水文干旱评价方法，以流域分布式水循环模型为技术平台，选择海河北系为典型流域，将地下水指标作为输入信息，研究能够反映流域地表和地下水资源综合变化的水文干旱评价方法，分析水文干旱发生的频率、强度、持续时间和影响范围，研判水文干旱在变化环境条件下的时空演变规律，辨识影响水文干旱的关键驱动因子，定量计算气候变化、下垫面变化和水资源开发利用等因素对流域水文干旱演变的贡献率，进而探析流域水文干旱演变的形成过程和驱动机制，为流域水资源管理及干旱科学应对提供科学依据。

水文干旱是联系气象、农业、社会经济干旱的一个关键环节。本项目基于游程理论、标准径流指数等传统水文干旱评价方法，以流域分布式水循环模型为技术平台，选择海河北系为典型流域，将地下水指标作为输入信息，研究提出了能够反映流域地表和地下水资源综合变化的水文干旱评价方法，分析了水文干旱发生的频率、强度、持续时间和影响范围，研判了水文干旱在变化环境条件下的时空演变规律，辨识了影响水文干旱的关键驱动因子，定量计算了气候变化、下垫面变化和水资源开发利用等因素对流域水文干旱演变的贡献率，进而探析了流域水文干旱演变的形成过程和驱动机制。典型案例研究结果表明，海河北系近54年发生的34次水文干旱主要集中在短历时、低强度、小面积区间内，空间上主要分布在张家口、大同及北京等地区；干旱指标的联动关系上，干旱历时、强度、面积指标间呈显著的线性或指数相关关系，90%的水文干旱历时低于40个月、干旱面积占比不超过43%，干旱强度低于9.0；在给定的干旱特征指标值（如干旱面积）条件下，另一干旱指标值越大（如强度越大）干旱发生概率越小，且存在明显的特征区间；单变量水文干旱重现期介于联合重现期和同现重现期之间。气候变化是引起水文干旱变化的主要驱动力，其对水文干旱驱动贡献度达57%；其次是水资源开发利用因素，对水文干旱相对驱动作用为33%；土地利用变化对水文干旱影响最小，仅占10%。人类活动对水文干旱相对驱动作用达43%，虽然仍小于气候变化因素，但其影响力存在进一步扩大的趋势。