Change of Natural Runoff and Contribution of the Natural and Artifical Factors to the Upper Reaches of Wei River
渭河上游天然径流变化及其自然与人为因素影响贡献量

Since the 1960s,the quantity of inflow entering Shanxi Province in the upper reaches of the Weihe River has decreased steadily,and in the 1990s,the quantity of natural runoff was only 60% of that in the 1960s.This article analyzed the relationship between natural runoff and precipitation,as well as quantified the extent to that effect of rainfall and non-rainfall on the decreased natural runoff.The result indicated that both rainfall and non-rainfall contributed to the decreased natural runoff in the upper reaches of the Weihe River,and the contribution rate of non-rainfall factors increased from the 1970s,becoming the major reason resulting in the decreased natural runoff in the upper reaches of the Weihe River.This article also analyzed the relationship between natural runoff and temperature,and the correlation coefficient of both is more than 0.47.It further analyzed the influence made by natural and artificial factors,in the case of abstract the factor of air temperature from non-precipitation factor.The results showed that natural factors contributed most before the 1980s,while it was replaced by artificial factors after the 1980s.The extent of the influence of the latter intensified gradually due to runoff decrease resulting from human activity modified underlying surface.