Variation and attribution of runoff over the upper reaches of Heihe River Basin

Based on the hydrological and meteorological data and land types in the upper reaches of Heihe River basin,variations and attribution of runoff over the study area were investigated using several statistical methods and Zhang Lu's empirical formula under Budyko framework.The results showed that:(1) The runoff increased significantly from 1960 to 2015 and changed abruptly in 1997 and 2004.The study period was divided into three stages:the base period of 1960-1997,the abrupt change period I of 1998-2004,and the abrupt change period II of 2005-2015;(2) The changes of precipitation,potential evapotranspiration and permanent glacial snow area were consistent with the changes of runoff to a certain extent.The increase of precipitation and the decrease of permanent glacial snow area had positive effects on runoff generation,while the increase of potential evapotranspiration had negative effects on runoff generation;(3) The contribution rates of precipitation,potential evapotranspiration and other factors (mainly the permanent glacial snowmelt) to runoff changes during abrupt change period I were 149%,-83% and 34%,respectively;and decreased to 138%、-35% and -3%,respectively,during abrupt change period II.

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