| With the continuous development of society,the global climate and environment have undergone significant changes,among which the water cycle system,which is closely related to human development,has also been greatly affected.Influenced by climate change and human activities,the frequent occurrence of extreme climatic events,droughts in the south and north,and the deterioration of water environment in China have constrained the sustainable socio-economic development of China.Therefore,it is important to study the changes of historical and future hydro-meteorological elements in the basin and the changes of runoff processes in the basin for the rational development and utilization of water resources in the basin,flood and drought prevention,ecological protection and water security in the basin.This paper takes Chengbi River Basin,a typical karst basin in southwest China,as the research object,and carries out research on the historical change pattern of hydro-meteorological elements,future climate prediction and the change pattern of future hydrological processes in karst basins under climate change,in order to provide scientific reference for the efficient utilization of water resources,water resources planning and management and water security in typical karst basins in southwest China.The study will provide scientific reference for the efficient utilization of water resources,water resources planning and management,and water security in typical karst basins in southwest China,and provide technical services to alleviate the current water shortage in southwest China and accelerate the national economic and social development in southwest China.The main results of this study are as follows:(1)The linear trend method,Modified Mann-Kendall trend test method,polar symmetric modal decomposition method,heuristic partitioning method,wavelet analysis and sliding Copula function were used to analyze the trend and variability of precipitation and runoff and the periodicity and variability of precipitation-runoff relationship in Chengbi River basin from 1979 to 2019.The results show that:the annual precipitation in Chengbi River basin shows a significant upward trend in general,with an annual surface precipitation growth rate of 6.9 mm/a;precipitation is unevenly distributed within the year,with precipitation in the basin and at each station concentrated in May to August;the annual runoff depth at the dam head station shows an upward trend in general,with a runoff depth growth rate of 1.906 mm/a;sudden changes in precipitation and runoff all occur in 2014;after 2010,precipitation and There is a positive phase-related significant cycle in the high-energy region after 2010,and a significant cycle of precipitation-runoff correlation in the low-energy region from 1979 to 1997;the precipitation-runoff relationship changed abruptly in 2013,and the optimal Copula function of the joint series changed from the Gumbel-Copula function to the Frank-Copula function.(2)Based on the evolution of historical hydro-meteorological elements in the basin,a hydrological model of Xin'an River was built on the Chengbi River basin,and the results showed that the model has good applicability in the simulation of hydrological processes in the Chengbi River basin.The deterministic coefficient DF and correlation coefficient R~2 of the model simulating daily-scale runoff reached 0.89,and the DF and R~2 of the validation period were 0.85 and 0.875,respectively;the deterministic coefficients of the model simulating monthly-scale runoff reached 0.95 and 0.92 for the rate period and validation period,respectively;the model simulation effect in the basin flood period was better than that in the non-flood period,and the simulation accuracy of the model in the flood and non-flood periods was 0.92 and 0.87,respectively.The results show that the model can basically reflect the rainfall-runoff process in the Chengbi River basin and can be used as a tool for future runoff response studies under climate change in the basin;Runoff changes during the historical period were mainly influenced by human activities and climate change,with the influence share of 34.1%and 65.9%,respectively.(3)The results of future daily precipitation,daily maximum temperature and daily minimum temperature in the Chengbi River basin output under the EC-Earth3 model SSP1-2.6,SSP2-4.5 and SSP5-8.5 scenarios show that the overall trend of increasing precipitation,maximum temperature and minimum temperature from 2020 to 2100,especially the future annual precipitation in the basin under the SSP5-8.5 scenario compared with the base year increases 13.2%,the annual average daily maximum temperature rises to 0.055°C/a,and the annual average daily minimum temperature increases at a rate of 0.060°C/a.(4)The rate-determined Xin'an River model was coupled with the EC-Earth3model output to derive the future runoff course of the Chengbi River basin.The results of the future runoff simulation in the basin show that the future annual runoff depth increases under the SSP1-2.6,SSP2-4.5 and SSP5-8.5 scenarios,and the multi-year average annual runoff depth increases by 167.57 mm,159.40 mm and 228.73 mm respectively under the three climate change scenarios compared with the base year;the future annual runoff change in the basin under the three climate change scenarios The peak of the basin under the three climate change scenarios is"unimodal",with the peak occurring earlier in July,and the peak changes are large,especially the peak of 164.99mm under the SSP5-8.5 scenario,which is 47.8%higher than the historical period;The dominant factor for future runoff changes in the basin is precipitation,with an average contribution of71.68%. |
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