黄土高原清水河流域降水-径流的响应关系

宁夏清水河流域地处黄土高原干旱、半干旱地区，选取清水河流域出口泉眼山水文站及气象站1989—2019年逐日径流和降水数据，并通过Chapman-Maxwell法对清水河流域径流时间序列进行基流分割，并将基流分割的结果应用于径流事件的分离，来探究径流事件对降水的响应特征。结果表明：(1)宁夏清水河流域降水量、径流量和基流量整体上均呈现上升趋势，经Mann—Kendall检验未发现突变显著的时间点，日降雨量10 mm以下的降水呈现增加趋势，年内降水主要分布在5—9月，占比达81.72%。(2)基于日径流时间序列，在清水河流域近30年间共分离出58次径流事件。在旱季降水总量与降雨强度显著相关，在土壤湿度和流域内水量存储条件的影响下，干旱时期的径流过程对事件前期降水响应较为敏感；在雨季，降水总量和降水强度是径流量的主要影响因素。(3)土壤水分对径流事件特征的影响具有阈值的变化，当前10天降水量未达5 mm时，峰值流量对其响应敏感。

Response Relationship Between Precipitation and Runoff in Qingshui River Basin on the Loess Plateau

The Qingshui River Basin in Ningxia is located in the arid and semi-arid transition area of the Loess Plateau. This paper selected the daily runoff and precipitation data of the Quanyanshan hydrological station and meteorological station in the Qingshui River Basin from 1989 to 2019, and used the Chapman-Maxwell method to divide the daily runoff time series of the basin. The result of base flow segmentation was applied to separate runoff events to further explore the response law of runoff events to precipitation. The results showed that: (1) The precipitation, runoff and base flow of the Qingshui River Basin in Ningxia showed an upward trend as a whole. The Mann-Kendall test showed there was no significant mutation time point. The precipitation with a daily rainfall of less than 10 mm showed an increasing trend. The annual precipitation was mainly distributed in May-September, accounting for 81.72%. (2) Based on the daily runoff time series, a total of 58 runoff events were isolated in the Qingshui River Basin in the past 30 years. Under drought conditions, the total amount of precipitation was significantly related to rainfall intensity. Under the influence of soil moisture and water storage, the runoff process under drought conditions was more sensitive to the precipitation response in the early stage of the event. In the rainy season, the total amount of precipitation and the precipitation intensity were the main factors influencing surface runoff. (3) The influence of soil moisture on the characteristics of runoff events had a threshold change. When the precipitation in the previous 10 days was less than 5 mm, the peak flow was sensitive to its response.