陕、甘干旱地区不同时段地表径流递减率的分析

On Progressive Decrease Rate of Surface Runoff at Different Periods in Arid Regions of Shaanxi and Gansu Provinces

根据陕西、甘肃部分地区气象、水文实测资料的分析，证明本区径流系数在逐年下降。在径流减少原因中，当时间尺度分别为４０ 年、３０ 年、２０ 年、１０ 年时，自然因素导致的径流递减率分别为１７．５％ ，３４ ．２ ％ ，５１．７ ％ ，７０．３％ ，径流量分别减少０ ．１４ ％ ，０ ．３４ ％ ，０ ．５２ ％ ，１％ 。

Based on climatic and hydrologic data in some regions of Shaanxi and Gansu provinces the decrease of surface runoff year by year has been proved. When time scales are 40,30,20 and 10 years the proportion of decrease of surface runoff caused by natural factors are 17.5%,34.2%,51.7% and 70.3% respectively and the proportion of decrease of surface runoff are 0.14%,0.34%,0.52% and 1% respectively.