Study On The Optimization Of Soil And Water Conservation In Small Watershed Based On InVEST Model

The small watershed of Xiping is a small watershed planned and controlled in 2014 in the agricultural comprehensive development and soil conservation project in Xilin County.It is of great significance to the ecological system service to optimize the adjustment of land use and the allocation of measures before and after the adjustment.Based on the In VEST model,the basic database on land use,meteorology,hydrology,vegetation,soil,evapotranspiration,and so on,is established by the In VEST model.The land suitability evaluation is carried out by the weighted superposition method.Then,the soil erosion status,the land use status and the experience of the former small watershed management can be based on the GIS realizes the layout optimization of the basin and achieves the adjustment of land use.In the In VEST model,the status of soil erosion,retention of sediment,water conservation and so on were used in the In VEST model before and after the adjustment of various factors in the basin.The correlation analysis method,the correlation of ecological services and the slope surface were used in the combination of land use,vegetation coverage and slope analysis.The degree of spatial aggregation was used to evaluate the development trend of ecological services before and after the adjustment,and the spatial distribution of integrated ecological services before and after the adjustment of the basin was obtained by using the combined superposition method.Through comprehensive analysis,the following conclusions are obtained:(1)The InVEST model is used to evaluate the ecological services before and after the adjustment of small watershed in Xiping.The annual average sediment transport modulus of the two station is 0.01~10.18 t/(hm2·a),and the small watershed of Xiping is a control basin selected mainly in the piggyback River,and the 10.40 t/(hm2·a)calculated by the model is basically comparable;the annual average rainfall in Baise and the average surface runoff depth are 1207.9mm and 419.43 mm respectively are also comparable with the average annual rainfall and the average water conservation 1129.33 mm and 434.21~439.94 mm calculated in this paper.(2)By soil erosion evaluation,the soil erosion modulus of Xiping small watershed is 10.40 t/(hm2·a)before adjustment,which is about two times of the allowable loss value.Soil erosion is relatively severe,and the control of soil and water conservation is particularly necessary.It is mainly reflected in the 15 degree ~35 degree area or cultivated land in watershed,which should be the key area for the prevention and control of soil erosion.By the evaluation of sediment retention and water conservation,the contribution rate of the comparative analysis of ecological services before and after the adjustment was concentrated on the terrain of forest land,Garden,grassland,high vegetation cover region and high slope region.Therefore,the protection of high slope or high vegetation area should be paid attention to in the process of control,and the ecological balance of the river basin should be prevented.(3)After the adjustment of land use in Xiping small watershed,the main aspects of the optimization are as follows: first,the soil erosion has been obviously contained;secondly,the soil conservation function of the Xiping small watershed is enhanced,and the soil erosion amount after the adjustment is obviously reduced.In turn,the water conservation function of Xiping small watershed is also showing an enhanced trend,which once again has a positive effect on the ecological environment of the watershed.(4)Through comprehensive assessment of ecological services and comprehensive analysis of land use,according to the intensity of human interference,the comprehensive classification of Xiping small stream ecosystem services is divided into high disturbance area,moderate disturbance area and low disturbance area.The high disturbance area is strongly disturbed by human disturbance,which should be the ecological control area of the basin,and the management measures such as slope change should be mainly in this area;the ecological system function service area in the moderate disturbed area is mainly plant measures,and the low disturbance area mainly is ecological restoration.