Function Evaluation Of Water Retention And Soil Conservation In Water Source Areas Based On InVEST Model

Quantitative evaluation of regional ecosystem service functions is the basis for rational use of natural resources and ecological construction.As a national important drinking water protection area,Danjiangkou Reservoir’s water conservation and soil conservation functions are important components of the ecosystem services of the river basin,and are also the key factors affecting the protection of water source areas.In this paper,the Hubei section of Danjiangkou reservoir area is used as the research area.Based on theories of physical geography,ecology,quantitative statistics,use the In VEST model,combined with RS and GIS technology methods,and use the climate,soil,hydrology,land use/cover,DEM and related statistical data to quantitative evaluate the service functions of water conservation and soil conservation ecosystems in the study area,analysis of their spatial and temporal changes,and quantitatively analyze the effects of land use/cover types,climate,underlying surface properties and other factors on water conservation and soil maintenance ecosystem service functions.The main research contents and results as follows:(1)The land use/cover types in the Danjiangkou Hubei Reservoir area are mainly forest land,followed by agricultural land with grassland,and again construction land with water area,and the least unused land.From 2007 to 2017,the area of agricultural land and unused land showed decreasing characteristics,while the area of forest land,grassland,construction land and water area showed increasing characteristics.During the 10 years,the land use/cover inflow and outflow in the Danjiangkou Hubei Reservoir Area was more intense,in which the inflow rate of forest land,grassland,construction land and waters was higher than the outflow rate,and the inflow rate of construction land is as high as 60.66%,the outflow rate of agricultural land and unused land is higher than the inflow rate,and the outflow rate of unused land is up to 74.66%.(2)From 2007 to 2017,the water supply in the Hubei Reservoir area of Danjiangkou showed a change characteristic of first decrease and then a significant increase,and it generally tended to rise.The average annual total water supply in the study area is 78.56×10~8m~3/a,and the average water supply depth is 356.32 mm/a.The spatial distribution pattern of water supply in the study area is generally high in the south,followed by the north,and low in the middle and east.(3)From 2007 to 2017,the water retention capacity of the Hubei section of Danjiangkou reservoir area changed first and then increased significantly,and it generally tended to rise.The average annual total water retention in the study area is 63.44×10~8m~3/a,and the average water retention is 287.56 mm/a.From 2007 to 2017,the spatial distribution trend of water retention functions in the Danjiangkou Hubei Reservoir area was consistent,generally showing a high in the south and west,and a low in the northeast.The area with significant increase in water retention capacity in the study area in the past 10 years is consistent with the area with high value of water retention,and the area with slow increase is consistent with the area with low water retention.(4)From 2007 to 2017,the soil retention capacity in the Hubei section of Danjiangkou reservoir area showed a change characteristic of first decrease and then a significant increase,and it generally tended to increase.The total soil conservation for many years is 30.04×10~8t,and the average soil conservation is 1416.25 t/hm~2.From 2007 to 2017,the spatial distribution pattern of soil conservation functions in the study area was basically the same,and generally showed the characteristics of high in the south and northwest and low in the east.The soil conservation function in the southern and northwestern regions has an obvious increasing trend,and the soil conservation function in the lower elevation regions such as the eastern region has a smaller increase.(5)From 2007 to 2017,the water retention capacity per unit area of different land use/cover types is as follows:woodland>grassland>agricultural land>construction land>unused land>water area;Climatic factors contribute greatly to the water retention capacity of the study area,and the soil and topographic factors in the nature of the underlying surface also have a certain influence on specific scales.(6)From 2007 to 2017,the soil retention capacity per unit area of different land use/cover types is as follows:woodland>grassland>agricultural land>construction land>unused land>water area;Climatic and topographical factors contribute greatly to the soil retention capacity of the study area,and soil factors also have a certain impact on specific scales.