Land Use/cover Change In The Haihe River Basin And Its Impact On Regional Evapotranspiration

For nearly a hundred years,the Haihe River basin has been the political and economic center of China,with many cities and dense population in the basin,as well as one of the most prominent areas in the north of China with the most contradictory water and soil resources.In recent years,the accelerated socio-economic development and urbanization have led to drastic land cover changes in the watershed,which in turn have affected surface evapotranspiration.Surface evapotranspiration is an important link in the water and energy cycles,so an in-depth study of land use dynamics and its impact on regional evapotranspiration is of great significance to the regional water balance and long-term stable socio-economic development.This paper conducts a study of Land Use and Land Cover Changes in the Haihe River Basin for three periods of land use data in 2000,2010 and 2020,and analyzes the direction,quantity and dynamic attitude of its dynamic change transfer as well as the trend state and index of land use types.Landsat remote sensing data for the June of 2000,2010 and 2020 within the Haihe River basin were also selected,and DEM data were introduced to correct the solar incident radiation,and then invert the surface parameters and simulate regional evapotranspiration based on the SEBAL model.On this basis,the effects of Land Use and Land Cover Changes on evapotranspiration in the Haihe River Basin are further explored,and countermeasures and suggestions are made for the future development planning of land resources in the Haihe River Basin.The results of the study are of great significance for the rational allocation of regional land resources and the control of evapotranspiration changes caused by the transformation of Land Use and Land Cover types.The main conclusions are as follows:(1)The Land Use and Land Cover types types in Haihe River basin include dry land,forest land,grassland,construction land,water body,paddy field and unused land,and dry land is the main one.Throughout the study period,a dry land,grassland,water area,paddy field and unused trend status index is less than zero,the area was reduced,forest land and construction land trend and state index greater than 0,the area was expanded,most of which source of newly-increased construction land for dry land,in addition,the dynamic space is the biggest construction land,0.98.The trend and state index of land use type change in the whole study area was 0.35,and Land Use and Land Cover Change reached a quasi-equilibrium state.(2)In this paper,we process Landsat 5 TM and Landsat 8 OLI?TIRS remote sensing data with the help of ENVI 5.3 and Arc GIS 10.5 software,and then invert the model parameters such as vegetation cover,surface specific radiation,surface albedo,and surface temperature,and then simulate the instantaneous evapotranspiration using SEBAL model,based on the evaporation ratio invariance method for time-scale diffusion,and finally derive monthly evapotranspiration.By comparing and analyzing the spatial distribution characteristics of evapotranspiration,it can be found that:the evapotranspiration of Haihe River Basin is obviously spatially heterogeneous,with high value areas concentrated in the eastern plains and low value areas appearing in the northwestern Taihang Mountain leeward slopes.In addition,in this paper,the simulated evapotranspiration was scatter-fitted with the MOD16 evapotranspiration data product of the same period,and the result was R~2=0.69,P<0.0001,indicating that the linear fit was good and could better reflect the evapotranspiration condition of the lower bedding surface.(3)Land Use and Land Cover types in the Haihe River Basin strongly influence the distribution of surface evapotranspiration,and significant regional differences in evapotranspiration are observed among land use/cover types.The changing pattern of evapotranspiration for various Land Use and Land Cover types is:paddy land>water>forest land>dry land>other land.Both the direction of transfer and the spatial dynamics of land use/cover change affect evapotranspiration,where the magnitude of the transfer is greater and the change in evapotranspiration is more pronounced.Among them,the increase of construction land will decrease the evapotranspiration,and the increase of forest land,dry land,grassland and water will increase the evapotranspiration,but from the last 20 years,the frequent human modification activities on the ground surface lead to the overall decreasing trend of evapotranspiration.