Optimal Allocation Of Soil And Water Conservation Measures In Typical Small Watershed In Southern Mountainous Area Of Ningxia

The construction of soil and water conservation measures is an important support for ecological protection and management,and an inherent requirement for promoting ecological protection and high-quality development of river basins.Based on sustainable development and governance,this study uses SWAT model to model the Ruhe River Basin,so as to determine the temporal and spatial distribution of runoff and sediment discharge.Based on the runoff and sediment discharge under different land use types,the ecological objective function of land use is constructed,and the land use structure of the basin is predicted based on the economic situation.FLUS model was used for spatial allocation of land use,different soil and water conservation scenarios were set according to the suitability of siltation dam construction,and the spatial optimization scheme of soil and water conservation scheme was selected according to the ecological benefits,carbon sequestration benefits and economic benefits.The main conclusions are as follows:(1)Based on SWAT model,the spatial and temporal distribution characteristics of water and sediment changes in the Ruhe River Basin were analyzed.The average annual runoff depth of the basin presents the characteristics of "large in the south and small in the north","large in the main stream and small in the tributaries".The average annual sediment transport modulus is "greater in the south than in the north" and "greater in the upper reaches than in the lower reaches".Under the current condition of soil and water loss control,the main sources of runoff and sediment production in the basin are grassland and cultivated land.(2)Spatial allocation of land use in Ruhe River Basin was carried out by using multiobjective function and FLUS model.Based on the reliability of FLUS model(Kappa=0.87),four future land use models,including natural development model(2035 land use),ecological development model,economic development model and balanced development model,were set up to represent the construction direction of soil and water conservation slope measures.The results showed that the future forest land construction was mainly in the southwest and northeast of the basin.The suitable areas for construction land expansion are concentrated in the southern and central parts of the basin.(3)The suitability of the construction of the Ruhe River Basin silt dam is evaluated and the potential sites for the construction of large silt dam are determined.The most important factor affecting the suitability of dam construction is the degree of soil erosion,which accounts for 35.03%,followed by river network density and rainfall,which accounts for 15.95%and 13.44%respectively.On the basis of satisfying the confidence(ROC-AUC=0.944),in the first and second gullies of the study area,the areas with high height suitable for the construction of silt DAMS were selected,and 51 potential sites for the construction of large silt DAMS were identified.(4)Reveal the suitable areas of different soil and water conservation measures in Ruhe River Basin.In some parts of the basin,such as the southwestern part of the basin,the reduction effect on sediment production is not obvious after the construction of new silting DAMS,and some areas even show an increasing trend,which indicates that this area is not suitable for the construction of silting DAMS,while in the south-central part of the basin,the effect of sediment reduction is significantly increased after the addition of silting DAMS.Therefore,In the process of soil and water loss control in the future,the construction of siltation DAMS will be concentrated in the south central area,while the biological measures such as forest and grass should be adopted in the southwest.