Analysis and Diagnosis of Changes in Annual Runoff in Kuye River Valley in North Shaanxi

Based on the 1961-2010 data of the flow in the Kuye River monitored by and stored in the Wenjiachuan Hydrologic Station, changes in runoff flow in the past 5 decades were characterized with moving average method and cumulative anomaly method and abrupt junctions in the runoff sequence identified with Mann-Kendall test method and sliding t test method. Then runoff characteristics and times of abrupt junctions worked out with various methods were analyzed and compared, and main causes triggering changes in runoff discussed preliminarily. Results show that the past 5 decades witnessed the Kuye River declining in runoff. The runoff time sequence could roughly be divided into three periods: 1961-1979, 1980-1998 and 1999-2010. Human activities, especially the large-scale exploitation of coal mines early this century, has rendered a great impact on runoff in the Kuye River Valley.