| In recent years,due to the combined impact of climate change and human activities,the spatiotemporal distribution characteristics of land use change and rainfall runoff in the Chaohu Lake Basin have undergone significant changes.To explore the impact of land use change on flood response processes in the Chaohu Lake Basin,based on multi-source satellite remote sensing image data,combined with field investigation data,and using human-machine interactive interpretation methods,a land use database for five periods from 1980 to 2020 was established.The spatiotemporal pattern of land use change in the Chaohu Lake Basin from 1980 to 2020 was analyzed.Based on the on-site rainfall and flow data of the Chaohu Lake Basin from 1970 to 2021,the characteristics and trend evolution of long-term series declining rainfall and runoff in the Chaohu Lake Basin were analyzed.The results of rainfall and runoff trend changes in the Chaohu Lake Basin from1970 to 2021 were obtained through Mann Kendall trend test,Pettitt mutation test,moving average method,cumulative anomaly method,and ITA trend test.By combining land use data and rainfall runoff data,a hydrological model was constructed to analyze the flood response in the Chaohu Lake Basin under land use changes.The main results are as follows:(1)Constructing a land use transfer matrix,the land use change in the Chaohu Lake Basin from 1980 to 2020 mainly manifested as an increase in construction land and a decrease in arable land and forest land;From 1980 to 2020,the impermeable area of the Chaohu Lake Basin increased from 1706 km~2to 2398 km~2,with an increase of 692 km~2,mainly due to the expansion of urban areas;The degree of landscape fragmentation in the study area has increased,leading to a decrease in dominant patches and a decrease in connectivity between patches.The shape of landscape patches in the watershed tends to be irregular and complex.(2)By analyzing the changes in rainfall and runoff through five trend and mutation testing methods,the overall rainfall in the Chaohu Lake Basin showed a trend of increasing first and then decreasing,with summer rainfall being the highest throughout the year;The number of days of rainfall at each station in the basin mainly shows a decreasing trend,while the rainfall shows an increasing trend,with an increase rate of 3.3 mm/a;The total runoff(Chaohu Sluice,Taoxi Sluice,Xiaotianer Sluice,and Yuxi Sluice)all showed a decreasing trend,with decreasing rates of 0.25,0.27,0.11,and 3.72,respectively×10~8m~3/10a;From the perspective of seasonal changes,rainfall in summer and winter shows an increasing trend,while in spring and autumn it shows a decreasing trend;Significant in winter changes.(3)Using the SCS runoff curve method to simulate the runoff in the Chaohu Basin,the spatial distribution of rainfall and runoff from 1980 to 2020 was obtained.The results showed that compared to 1980,the runoff in 2020 increased by 6.11%,2.61%,and 0.96%under different rainfall conditions(50 mm,100 mm,and 250 mm),with significant changes in Hefei region;Construct a HEC-HMS hydrological model for the Fengle River Basin,using SCS runoff curve method,SCS unit hydrograph method,exponential decline method,and Muskingen method to simulate the four stages of runoff generation,confluence,base flow,and river evolution.By utilizing the built-in parameter optimization function of the model and using the cyclic asymptotic method to optimize and adjust the parameters,the simulation results of rainfall and runoff in 1980,2000,and 2020 were obtained.The results showed that the Nash coefficients of hydrological simulations in1980,2000,and 2020 were 0.721,0.616,and 0.596,respectively.The relative errors of peak flow were-2.8%,-39.6%,and-16.8%,respectively,and the relative errors of runoff were-12.6%,19.1%,and 2.1%,respectively.The peak time differences were all within one day,and the simulation results reached a qualified level or above.The simulation results are reasonable and can provide reference for flood prevention and control work. |
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