Runoff Depth Variation Process and Driving Mechanism of Upper Reaches of Marsh Stream

Abstract

Through the double mass curves analysis, it concluded that the relationship between the areal and the runoff depth within upper reaches of the Naoli River, the Naoli River basin had experienced a great change since 1963, especially the runoff coefficient which appeared in a decreasing trend. By adopting the runoff coefficient difference Rank and T test (α=0.05,n1=7,n2=43,T=255,T1α=108.52,T2α=248.47, T＞T2α＞T1α), it also concluded that there was no consistency between the runoff coefficient series from 1956 to 1962 and the ones from 1963 to 2005. By analyzing the frequency curves of precipitation-runoff depth, it indicated that, under the same precipitation frequency, the runoff coefficient in 1963-2005 was much smaller than that in 1956-1962. The research results revealed that: (1) The precipitation was the key driving force to runoff variation; (2) The land use/cover changes posed by human activities was one of important causes contributing to runoff coefficient mutation in the catchment area; (3)The runoff depth variation was mainly controlled by the Longtouqiao reservoir and the water consumption was influenced by irrigation of paddy field since 2001.