| China is one of the countries with the most serious soil erosion in the world,and the water and sand changes can reflect the development of the watershed itself,the degree of soil erosion and the ecological environment condition.Based on the remote sensing images from 1980 to 2020,this paper extracts and analyzes the land use change pattern and driving factors of the watershed,further constructs the land use prediction model and completes the model accuracy verification;collects and organizes the measured water and sand data from 1960 to 2019 in the strain water basin and analyzes its change pattern to study the water and sand evolution and its response to climate change and human activities;constructs the A semi-distributed hydrological model was constructed and validated to quantify the influence of climate and land use on water-sediment processes;finally,three future land use scenarios were constructed to investigate the influence of future land use scenarios on runoff and sand transport based on the hydrological model and land use prediction model,which provide references for watershed planning and erosion control.The main conclusions obtained from the study are.(1)During the period of 1980-2020 in the strained water basin,the forest area decreased by 7.36%;the arable land area decreased by 27.92%;the area of construction land increased by 552.71%,and most of the transferred area of arable land and forest land was transferred to construction land,and the sudden change of land use occurred between 1995 and 2000.The land use prediction model was constructed,and the empirical Kappa coefficient was 0.8618,indicating that the model has a good simulation effect and can be used for land use prediction and future scenario construction in the strained water basin.(2)The contribution of climate and human activities to the increase of runoff is 49.52%and 50.48%respectively around 1988,while the contribution of climate and human activities to the decrease of sand transport is 3.44%and 96.56%respectively around 1998,the abrupt change point of runoff in the watershed.The results indicate that the increase in basin runoff after 1988 is the result of the combined effect of climate change and changes in human activities,while the decrease in basin sand transport after 1998 is mainly attributed to human activities.(3)The hydrological model was constructed and its applicability was evaluated.The average relative errors in the runoff rate determination and validation stages were 5.93%and 15.37%,the correlation coefficients were 0.92 and 0.88,and the Nash coefficients were 0.89 and 0.87,respectively;the average relative errors in the sand transport rate determination and validation stages were 32.38%and 42.65%,and the Nash coefficients were 0.73 and 0.64,respectively.It basically meets the requirements of simulation accuracy and can be used to further construct simulation scenarios and analyze the impact of watershed subsurface changes on water and sand.(4)Based on the HSPF model,we input different climate and land use scenarios to evaluate the contribution of climate and land use changes to water-sediment changes in the watershed.The model simulation results show that the contribution of climate and land use changes to the increase of runoff volume is 57.95%and 42.05%,and the contribution to the decrease of sand transport volume is 16.90%and 83.10%,respectively.(5)Three future land use scenarios were constructed based on the land use prediction model,and water and sand changes under the three future scenarios were simulated with the help of the hydrological model.The simulation results show that the arable land protection model does not significantly aggravate the soil erosion problem while safeguarding the arable land area,and can also take into account the socio-economic development and urbanization construction. |
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