Runoff Modeling In A Multi-Scenario Land-use Transformation Based On The Swat Model

Climate disturbance and the expansion of human living environment are the primary factors which influence the development of hydrology and water resources in the Zuli River Catchment.The Zuli River,a tributary of the Yellow River,is located in the semi-arid region of the western Loess Plateau.The delicate ecological environment results in the poor protection of vegetation to the topsoil,thus the ability of this region to resist sudden hydrological events failed,such as a storm.In recent years,because of the transformation of the climatic zone in Western China,precipitation in this area has gradually increased,resulting in more serious soil erosion.At the same time,the rising water demand as well as the further pollutant emissions,which are put the environmental pollution of this area into a severer situation.It attracts more and more attention on how to deal with the impact of climate and social environmental changes on the ecological environment of this river basin.Based on the above reasons,this paper selects Soil and Water Assessment Tool?SWAT?model to interpret the response of land use structure development transformation to the hydrological process of the Zuli River Catchment based on the climate scenario model,which is of great reference value for protecting and exploiting the water resources of the Zuli River Catchment reasonably,as well as restorating and controlling of the underlying surface.The research content and conclusions mainly include:?1?Construct the SWAT model of the Zuli River Catchment and complete the parameter calibration.Integrate the spatial attribute information of the Zuli River Catchment to complete the establishment of the SWAT model database.Refine the entire watershed into 28 sub-basins,overlaying the land use type,soil type as well as the slope,and then fuse the three images to divide the Zuli River Catchment into 137hydrological response units?HRUs?.The SWAT-CUP platform was built to complete the sensitivity analysis of 19 parameters,and after determine their order,choose the SUFI-2 algorithm to optimize them,then use the measured monthly runoff data in the river basin to evaluate the accuracy of the SWAT runoff simulation.The results showed that the R² and E_NS values are all reasonable,which can be concluded that the SWAT model is applicable to the Zuli River Catchment.?2?Respond to hydrological process of the Zuli River Catchment based on future climate model.Under the RCP4.5?medium-low scenario?,RCP8.5?high scenario?greenhouse gas emission and radiative forcing scenarios,this research compared the characteristics of meteorological factors such as the predicted rainfall and temperature in the Zuli River Catchment from 2020 to 2100.Under these two scenarios,the average annual temperature of the Zuli River Catchment will increase by 0.17?/10a and 0.46?/10a respectively in the next 70 years,and the temperature increases will be 1.12?and 3.22?comparing to the base period;the average annual rainfall will increase by0.55 mm/10a and 5.11 mm/10a,and the rainfall increases will be 3.86 mm and 35.78mm comparing to the base period;under the RCP4.5 scenario,the average annual runoff of the Zuli River Catchment is slowly increasing in the next 70 years,increasing by0.08 cm³/s from the base period;the average annual runoff under the RCP8.5 scenario is lead to a slowly downward trend,which is 0.007cm³/s lower than the base period;affected by the high temperature in the RCP8.5 scenario,the precipitation increased simultaneously,but it inhibited the formation of the runoff,instead of promoting it positively.?3?Analysis of the response of land use types in the Zuli River Catchment to hydrological processes.Three phases of land use images in 1995,2005,2015 and four frames of extreme land use artifact images were used to realize the runoff simulation.The results showed that under the influence of topography and agrotypes,forest land and cultivated land in the different regions of the Zuli River Catchment play different roles on the formation of the runoff;on the contrary,urban land,industrial land and grassland are relevant to the formation of the runoff,which are,when the area of urban land and industrial land increase,the runoff will increase correspondingly,while the increase of the grassland area will relatively decrease the runoff.From large to small,the contribution of each land use type to runoff is:urban land and industrial land>cultivated land>forest land>grassland.?4?Predict future land use scenarios and runoff in the Zuli River Catchment.From2015 to 2035,the area of cultivated land,forest land,urban land and industrial land will increase,while the area of grasslands and water area will decrease,among which 67.25%of the new sources of urban land and industrial land area are cultivated land,and 15.93%are grassland.But the reason why the cultivated land area rises is that the grassland area transferred in,and 95.84%of the new cultivated land area come from grassland.In the same climatic conditions,the runoff of Guochengyi hydrological station and Dingxi hydrological station under the 2035 land use type scenario will significantly higher than the data in 2015,mainly due to the increase of urban land,industrial land,as well as the diminishment of grassland area.However,there is no obvious difference in runoff simulation between the 2035 and 2015 land use type scenarios at Huining hydrological station,the main reason is that the area of the slope of the terrain in the Huining Basin is less than 25 degrees,the farmland reclamation and urban construction are limited,and the area of forest land Increase related.