The Relationship between Annual Rainfall and Surface Runoff in Yinghe Watershed in the Upstream of the Huaihe River Basin

Based on the observation data from 1981 to 2004,characteristics of annual precipitation and runoff and their relationship in the typical watershed,Yinghe catchment,of the Huaihe river basin are systemically analyzed.The results show that there is a clear difference in annual precipitation and runoff flow year by year with 0.28 and 0.45 variance coefficient respectively.The rainfall amounts distribution centralizes in the flood-months,with 82.1% of the total occurring from May to October.Annual rainfall amount is a decisive factor of annual runoff.It implies that there is a rich opportunities of flood and drought disaster.The analysis of the typical year's data shows that the even rainfall pattern is dominant.There is a very clear positive correlation relationship between annual precipitation and runoff flow,between runoff ratio and rainfall amount in the flood-months either.