Analysis Of Response Of Runoff To Land-use Change In The Upper Hutuo River Basin

Land use is one of the critical factors influencing local hydrological processes.It can have a significantly impact on the processes involved in runoff production and alters the distribution of local vegetation,crop cultivation types,and land use patterns in watersheds.Measuring the influence of land use change on hydrological processes has become a popular research topic in hydrology and water resources.Thus,mastering the trend of watershed runoff evolution under land use changes is of great significance for regional land use development planning and regional water resource planning.This study selected Hutuo River basin as the research object,analyzing the land use in the basin above Hutuo River Huangbizhuang Reservoir in five periods:1980,1990,2000,2010,and 2020,and obtained the change patterns of land use types in each period to investigate the response of runoff to land use changes in the upper Hutuo River basin.In addition,a soil and water assessment tool(SWAT)model was established to simulate the monthly runoff processes of the upper Hutuo River Basin under five different land use scenarios from 1960 to 2020 for further exploring the impact of land use changes on runoff.The main conclusions are as follows:(1)The SWAT hydrology model was established in the study area.With the use of the upper Hutuo River Basin’s DEM data,soil data,five-phase land use data,and the1960-2020 daily meteorological data,the five-phase land use nodes were applied to divide the years of 1960-2020 into five simulation periods for simulating the runoff processes under the land use scenarios of each period.Then SWAT-CUP was used to calibrate and validate the model parameters at different simulation periods,with the results of R~2 above 0.6 and NSE above 0.5 during the calibration and validation periods of the model,indicating that the SWAT model has high simulation accuracy and good applicability in the upper Hutuo River Basin.(2)The change rules of land use were analyzed.According to the requirements of the SWAT model for land use data,the land use data in the study area was reclassified into six categories:cultivated land,forest land,grassland,water area,urban construction land,and unused land.The changes in land use in the study area from 1980 to 2020were analyzed from two aspects:the change rate of different land use types during different periods,and the land use transfer matrix.It was found that the area of forest land,grassland,and agricultural land in the upper Hutuo River Basin decreased by 3.1%(704 km~2)from 1980 to 2020.However,the area of land for urban construction has shown a rapidly growing trend,with the area expanding by 1.5 times from 1980 to 2020.(3)The impact of land use changes on runoff was quantitatively analyzed.Based on the five-phase land use data,the runoff processes under different land use scenarios in the study area from 1960 to 2020 were simulated and compared with the natural runoff process to analyze the impact of land use changes on the runoff in the upper Hutuo River Basin.The results have shown that from 1980 to 2020,with the area increase of urban construction land and the area decrease of arable land,forest land,and grassland,the simulated flood peak flow and annual runoff volume in the upper Hutuo River Basin increased by 25.83%,and 18.73%,respectively.However,with the continuous growth of the urban construction land area in the basin,the flood peak flow and annual runoff volume have shown a slow growth trend.