Impact Of Land Use Change On Watershed Runoff Based On SWAT Model

The study on the effect of catchment runoff to land use change has important significance on reasonable planning land use pattern and promoting social and economic development.This thesis takes "Impact of land use change on watershed runoff based on SWAT model" as title to carry out research,it's main content and the related results are as follows:The basic database of SWAT model is constructed.The basic data of the Chengbihe reservoir watershed are collected and processed,including DEM data,the land use data,soil data,meteorological data and the other data SWAT model needed.The SWAT model's input parameters and its applicable value were determined.The SWAT-CUP is selected to calibrate and validate the input parameters,the values of 13 sensitive parameters are determined.The five parameters which have great influence on the runoff simulation results are:SOL BD(Moist bulk density),CN2(Runoff curve number),ALPHA BF(Base flow coefficient,),CH_N2(Manning coefficient of main channel),ESCO(Compensation coefficient of soil evaporation).The monthly runoff data of the Bashou hydrological station in Chengbihe reservoir watershed from 1983 to 1993 are used for model calibration by using SWAT-CUP.In the calibration period,Ens=0.85,Re=1.13%and R2=0.86.The monthly data from 1994 to 2015 are used for model validation.In the validation period,Ens=0.6,1Re=8.3%and R2=0.71.The results can meet the evaluation criteria.Three kinds of land use condition based on the land use in 2015 are assumed by the extreme land use method,which are S1(agricultural situation),S2(forest land situation)and S3(grassland situation).The land use situation in 1995 is recorded as L1.The land use situation in 2015 is recorded as L2.Bring the five situation to SWAT Model.Conclusions are as follows:The most runoff is S1(agricultural situation),which is 10.1%higher than L2.The less runoff is S3(grassland situation),which is 18.5%lower than L2.The least runoff is S2(forest land situation),which is 24.6%lower than L2.In water yield and surface runoff,S1(agricultural situation)is the most,followed by S3(grassland situation),and the least is S2(forest land situation).The situation of underground runoff and interflow just opposite to surface runoff.The evapotranspiration of S2(forest land situation)is equal to S3(grassland situation)and is higher than S1(agricultural situation).In three kinds of land use condition,the annual runoff coefficient of agricultural situation is the most,forest land situation is almost equal to grassland situation.Conservation index of agricultural situation is more than grassland situation and agricultural situation,which means that in the ability of water conservation,forest land is the most,followed by grassland,and the least is agricultural land.