Study On Applicability Of Distributed Hydrological Model SWAT On Runoff Simulation In The Source Region Of The Yellow River

The source region of the Yellow River,above Tangnaihai is an important water supply source and water onservation area.Runoff of the source regions of the Yellow River which is called the“water tower”accounts for more than 35%of the total runoff of the Yellow River basin.In recent years,due to the influence climate change and human activities,the runoff in this region showed a downward trend.Selecting the source region of the Yellow River as study area,this paper analyzes the variation characteristics of hydrological elements,quantifies the impacts of precipitation and human activities on runoff by using the method of cumulative slope rate of change,uses SWATmodel driven by CMADS to simulate the runoff,sets up different land use and cover scenarios to simulate the runoff and analyzes the impacts of different land types on runoff.The main conclusions are as follows:1.Some basic characteristics and trend prediction of hydrological cycle elements are as follows:?1?From 1960 to 2011,annual precipitation showed a decresing trend.Annual precipitation sequence mutated in 1990.Flood season precipitation seque nce mutated in 1986 and 2003.Non-flood season precipitation sequencemutated in 1981 and 2000.?2?From 1960 to 2011,the runoff of the source region of the Yellow River showed a decreasing trend.From the 1960s to the 1980s,the runoff was relatively large.From the 1990s to the 21^st century,the runoff decresed significantly.1990 was the abrupt change year of runoff series.?3?The change trend of precipitation and runoff was basically the same.1990was a mutation year of the runoff seguence.After 1990,the contribution of precipitation was 37.96%,while that of human activities was 62.04%.Obviously,human activities were the main factor which caused the change of runoff.2.Some conclusions about parameter calibration and model simulation are as follows:?1?The first three paramaters with the highest sensitivity are SCS runoff curve number,soil saturated bulk density and river effective permeability coefficient.?2?From the simulation results in the calibration and verification period,there is a good correlation between simulated and measured runoff in the source region of the Yellow Revier.Therefore,SWAT model has q good applicability in the source region of the Yellow River.The simulation results are different in different time scales.The simulation result on the monthly scale is more accuracy than that on the daily scale.?3?SWAT models were driven by the Chinese atmospheric assimilation data version 1.0 and the tranditional meterological data.The result showed that three evaluation indexes of simulation results,including the relative erro,Nash Scuttcliffe coefficient and correlation coefficient,driven by CMADS we re higher than those of the traditional meterological data.CMADS can represent perfectly the surface atomospheric characteristics of underlying surface in the sour ce region of the Yellow River.3.The conclusion about simulations under different land use and cover change scenarios are as follows:In the source region of the Yellow River,runoff yield are different under different land use and cover scenarios.The increase of grassland area,to a certain extent,will lead to the decrease of runoff.The increase of bare land area will lead to the increase of runoff.When the surface is completely bare with vegetation,the simulation runoff reaches the maximum valus.Its runoff will increase by 41.65%.