Impact Of Land Use And Climate Change On Runoff In The Yanhe River Basin Using SWAT Model Simulation

This paper takes the Yanhe River basin as the study area,and in order to reveal the impact of land use change and climate change on runoff in the Yanhe River basin,SWAT(Soil and Water Assessment Tool)is selected to construct a watershed model,and the response relationships between land use change and climate change and watershed runoff are quantitatively analyzed by setting different land use change and climate change scenarios.The following main conclusions were drawn from this study:(1)In this paper,14 hydrological model parameters of the SWAT model of the Yanhe River basin were determined,and sensitivity analysis was performed on these14 parameters using SWAT-CUP,and then the rate of these parameters was determined.The rate of the model parameters in this study is 0.92 and 0.84 for R2 and NS respectively,and 0.86 and 0.81 for R2 and NS respectively in the validation period.meet the accuracy requirements of the model,therefore,the established SWAT model is applicable in the Yanhe River basin.(2)In order to investigate the impact of land use change on runoff in the Yanhe River Basin,three land use scenarios were designed using the extreme land use scenario method,namely,all cropland to grassland,all cropland to woodland scenario,and all woodland to grassland scenario.The results of the study showed that the contribution of land use types to the increase of runoff in the Yanhe River basin was in the order of the size of cultivated land,grassland,and woodland;woodland had the strongest waterholding capacity,followed by grassland;the conversion of woodland to grassland reduced the impact of plant interception,infiltration,and evaporation on runoff,thus causing a decrease in runoff.(3)In order to investigate the runoff changes in the Yanhe River basin before and after the implementation of the reforestation and grass restoration project,the runoff changes in the Yanhe River basin under the land use scenario in 1990 were compared with 2010 as the reference period.The results showed that the runoff in 2010 decreased by 5.38m3/s compared with 1990,indicating that the vegetation increased and the runoff in the watershed decreased after the implementation of the reforestation and grass restoration project,and the soil and water conservation capacity in the watershed was effectively restored.It further confirms that the fallow forest and grass restoration project can effectively reduce the harm of soil erosion,and the vegetation restoration can improve the ecological environment and promote the enhancement of ecosystem services.(4)To investigate the response of runoff to climate change in the Yanhe River basin,25 scenarios were designed using arbitrary assumptions to analyze the response of runoff to changes in climate factors.The results show that the annual runoff in the Yanhe River basin is negatively correlated with the temperature,and the runoff tends to decrease as the temperature increases;the annual runoff in the Yanhe River basin is positively correlated with the precipitation,and the runoff tends to increase as the precipitation increases;the contribution of precipitation to the annual runoff in the Yanhe River basin is the greatest,and the sensitivity of the runoff to the change of precipitation is stronger than that of the change of temperature;the annual runoff in the Yanhe River basin is more sensitive to the change of temperature and The annual runoff in the Yanhe River basin is more significant under the intervention of both temperature and precipitation factors.(5)Combined climate change scenarios and land use change scenarios were used to synthesize the response of runoff in the Yanhe River basin to climate change and land use change.From the simulation results,it can be seen that the change of runoff in the basin is generally decreasing under the combined scenario.This indicates that land use change and climate change have a flow reduction effect on runoff.However,the effect of climate change on runoff is greater than that of land use change.Therefore,in the context of climate change,when formulating future land use planning in the Yanhe River basin,we should reasonably adjust the direction of land use planning,deeply consider the impact of different land use types on watershed runoff,protect grasslands and woodlands,increase the implementation of the project of returning farmland to forests and grasses,optimize water resources management objectives,maintain the reasonable development and utilization of water resources,reduce the negative effects of climate change on water resources,and jointly maintain the The ecological stability of the Yanhe River Basin.