Analysis on Runoff Variation Characteristics of Tuwei River During 1967—2007

The article analyzed inter-annual and annual runoff variation in Tuwei River with the runoff data from 1967 to 2007 at Gaojiabao Station and the series of annual and monthly runoff were tested by Mann-Kendall method.The results show that a) annual runoff from 1967 to 2007 has reduced significantly;b) distribution of inter-annual runoff is bimodal,each month runoff from 1967 to 2007 shows a decreasing trend.The proportion of flood season runoff of the total annual runoff has declined gradually,while the proportion of non-flood one has raised.The uniform coefficient and runoff concentration degree are significantly reduced after 1970 than before and;c) the increasing temperature,water conservation management and water conservancy construction are the main causes of Tuwei River runoff reduction and distribution uniformity.