黄河源区气候对径流的影响分析

根据对降水响应速度的快慢,径流又可分为直接径流和基流。基流一般定义为河川径流中来自于地下蓄水或者其他延迟水源的成分,代表地下水出流;直接径流表示对降水事件的直接响应。从这一思路出发,文中在分析降水到总径流、直接径流和基流的转化率的基础上分析了气候变化对径流的影响。研究发现,黄河源区的径流系数随降水量的增加而增大,随气温升高而降低;径流随着降水的增加而增加。20世纪90年代降水减少和气温的大幅度升高是黄河源区径流减少的重要原因。区间子流域分析表明,不同的子流域气温和降水对径流的影响不同,在吉迈以上区间,年气温比较低,气温是影响径流系数的主要因子,径流随着气温的升高而降低,降水对径流的影响比较小;在吉迈—玛曲区间,直接径流量/降水量主要受降水的影响,总径流量/降水量、基流量/降水量随降水增加而升高,随气温升高而降低。总径流和基流随降水的增加而增大,随气温的升高而减少;在玛曲—唐乃亥区间,径流系数随着降水量的增加而增加,直接径流量/降水量随气温的升高而降低,降水是径流的主要影响因素。

Impact of climate on runoff in the source regions of the Yellow river

Runoff regeneration processes are one of the key processes in the water cycles. Runoff can be separated into direct runoff and baseflow according to the response rate to precipitation.The baseflow is generally defined as the part of river runoff come from groundwater storage and other delayed water, while the direct runoff is defined as the part of river runoff direct response to precipitation. Based on this theory, the impact of climate factors on runoff is analyzed by investigating the conversion rate of precipitation to total runoff, baseflow and direct runoff. In the sources regions of the Yellow river, runoff coefficient was in positive relation with precipitation and in negative relation with air temperature; runoff increased with the precipitation. In the 1990s the sharp decrease of precipitation and increase of temperature contributed to the decrease of runoff. Impacts of climate on runoff were different in different subbasin in the source regions of the Yellow river. In subbasins above Jimai hydrologic station with mean annual temperature below -3.0 ℃, temperature was the key factors affecting runoff. With the increase of temperature runoff will decrease. In subbasin between Jimai hydrologic station and Maqu, runoff and baseflow both increased with the increase of precipitation, and decreased with the increase of temperature. In subbasin between Maqu and Tangnaihai hydrologic stations, precipitation was the vital climate factor affecting runoff(including baseflow and direct flow and total runoff), only direct flow are slightly influenced by temperature.