水文变异情势下极端水文事件的群发性研究

The variation of hydrological elements aggravated the frequency, the scope and extent of the damage of extreme hydrological events under under the changing environment，its group-occurring and persistent increase brings new problems and challenges for disaster prevention and mitigation.The application of the target is to reveal the time and space group-occurring characteristics of extreme hydrological events (extreme precipitation, extreme temperature and extreme runoff) under hydrological variation situation, and its response to runoff variation relationships in the Wei river basin. Based on the nonlinear dynamics theory, put forward hydrological variation comprehensive diagnostic method and established the elastic coefficient method model to diagnose runoff variation point and its causes, finally determined the variation point and interval; The paper used such as percentile method to determine the threshold of extreme hydrological events , and delineated the cluster area of extreme hydrological events using the theory of space point process combined the kth-order nearest-distance arithmetic delineating cluster events to analyze and extreme hydrological events inter-decadal and regional clusters characteristics .Using the group-occurring index to analyze the group-occurring of extreme hydrological events before and after the runoff change point ，to reveal the hydrological variation mechanism, the group-occurring area of extreme hydrological events, the relationship between mass site and its response to runoff variation relationship, and put forward corresponding countermeasures. The research results can provide a scientific basis for disaster prevention and mitigation in Weihe and similar basin.

变化环境下流域水文要素发生变异，加剧了极端水文事件的频次、范围和破坏程度，其群发性和持续性增大，给防灾减灾带来了新问题和新挑战。本项目以渭河流域为研究对象，以揭示水文变异情势下极端水文事件（极端降水、极端径流、极端温度）时空群发性特征，及其对径流变异的响应关系为目标。基于非线性动力学理论，提出水文变异综合诊断方法，建立弹性系数法模型，诊断径流的变异点及其成因，最终确定流域变异点及区间；采用百分值法等确定极端水文事件阈值，利用空间点过程理论结合“K阶最近邻距离提取算法”，提取极端水文事件群发区域，分析极端水文事件年际、代际以及区域性群发性特征；采用群发性指数，对比分析径流变异点前后极端水文事件的时空群发性特征，揭示水文变异的致灾机理、极端水文事件群发区域、群发站点之间的相互关系及其对径流变异的响应关系，并提出相应的防治对策。研究成果可为渭河和类似流域防灾减灾提供科学依据。

水文变异情况下，极端水文事件的频次、范围以及破坏程度发生了很大的改变，呈现区域群发性的特征，给区域水安全带来了新的难题。渭河流域为干旱半干旱典型代表区域，在气候变化变化和人类活动影响下，水文要素发生了变异，极端水文事件呈现区域群发性的特征，本研究在降水、径流、蒸发和温度趋势性变化分析的基础之上分析了趋势性、持续性和复杂性的时空特征；基于非线性动力学理论的水文变异综合诊断理论，通过蒙特卡罗模拟对比分析了各种不同的非线性动力学方法的优缺点，最后找出适合流域变异争端的方法。在水文变异分析的基础上，采用百分位阈值法确定了极端高温事件和极端降水事件的阈值，构建了流域各站点的频数权重，并通过空间过程理论的k-mean均值聚类提取了渭河流域不同代际的群发区域、分析了极端高温事件、极端降水事件的年际、代际以及区域群发性特征；采用Gumbe-Hougaard Copula、Frank Copula和Clayton Copula函数分别构造干旱历时和干旱烈度、干旱历时和烈度峰值以及干旱烈度和烈度峰值之间的二维关系，从而对渭河流域近60年的极端干旱区域特性进行分析，在此基础上计算并选取了标准降水指数、综合干旱指数和降水距平百分率，并通过模糊物元理论将这三种干旱评价指标结合起来构建了一种新的评价方法并与已发生的干旱进行分析对比，完成了流域内极端干旱变化情况的定量评价。研究成果可为渭河和类似流域防灾减灾提供科学依据。