| In recent years,global climate change has become the focus of world attention,and it affects the ecological environment,human production and life in many ways.Among them,the hydrological cycle process of the basin is significantly affected by climate change.Changes in factors such as temperature,precipitation and evaporation will cause changes in the frequency and intensity of the runoff process in the basin,which will affect the amount of water resources and their temporal and spatial distribution,and bring uncertainty to runoff forecasts and water resources prediction.Therefore,carrying out regional hydrological cycle simulation research under the influence of climate change is the foundation of regional water resources management and sustainable utilization.The Changbai Mountain region is rich in water resources and is the source of the Songhua River,Tumen River,and Yalu River.It accounts for78.6% of the total water resources in Jilin Province.It is important to carry out research on environmental changes and water resources evolution laws in the Changbai Mountains,and correctly understand the mechanism of climate runoff changes and accurately grasping the future trend of runoff changes.Because those are related to the ecological security of the region and the sustainable development of the society and economy.Meanwhile,those are also the basis for the efficient use of regional water resources and their safety guarantee.In this study,the Erdao Songhua River Basin,a typical watershed in the Changbai Mountains,was selected as the study area.Based on the long-term sequence of meteorological and hydrological element changes in the historical period of the study area.The distributed hydrological model HEC-HMS was selected to carry out rainfall runoff simulation and verification in the basin,and to study the changes in regional climate conditions and their response to runoff under different climate change scenarios in the future.The main conclusions obtained in this paper are as follows:(1)The Mann-Kendall test and sliding T test were used to analyze the change characteristics of temperature,rainfall and potential evapotranspiration in the Erdao Songhua River Basin from 1957 to 2017.The results showed that the temperature in the Erdao Songhua River Basin showed a clear upward trend.There is a large temperature difference between the months of the year.January has the lowest temperature,and July and August have the highest temperature.Unlike the general reduction in rainfall throughout the country,the rainfall in the basin first showed a downward trend in the first 20 years,and then began to rise sharply in the following40 years.The overall trend is slightly increasing,with a trend rate of 2.31 mm/10 a.Concentrated precipitation in summer from June to August,which is manifested as rain and heat at the same time.The Penman-Monteith formula is used to calculate the potential evapotranspiration in the basin,and the overall change has increased significantly in the past 60 years.The year 2009 and 2013 were sudden changes,and the evapotranspiration from May to August of the year was relatively large.(2)From 1965 to 1984,the water levels of Hanyangtun Station,Dadianzi Station,Songjiang Station and Erdaobaihe Station in the basin did not change significantly,and the flow showed a slight downward trend.Except for Erdaobaihe Station located in the source area of Changbai Mountain,the distribution of flow during the year did not change much.The other three stations all had a large flow from April to August,which was related to the natural conditions of the study area with snowmelt in spring and rain in summer.(3)Based on the elevation,land use,soil,meteorological and hydrological data of the study area,construct the watershed HEC-HMS model during the flood season from 2006 to 2017.Then divide the watershed into 15 sub-units,manually adjust the parameters through manual trial and error method,and through the certainty coefficient DC and other indicators for simulation accuracy evaluation.It is concluded that the model has the best simulation effect on the peak present time and the peak flow rate during the period of rate and the verification period,and the pass rate reaches 91.7%.The comprehensive evaluation index shows that the simulation pass rate is 75%,and the DC average of the qualified year reaches 0.705.It shows that the HEC-HMS model is more reliable in the rainfall and runoff simulation results of Erdao Songhua River Basin during the flood season,and the simulation effect of the year with heavy rainfall is better than that of the year with less rainfall.(4)In the next 30 years(2021-2050),under the two climate scenarios of SSP2-4.5 and SSP5-8.5,the rainfall in the basin will show an overall upward trend,average annual rainfall is higher under SSP2-4.5 scenario.Rainfall will be more evenly distributed during the coming year,with lower rainfall during the flood season(June-September)and higher rainfall in other months.Used the established HEC-HMS model to simulate the flow at the outlet of the basin during the next 30 years of flood season(June-September),it was found that the flow in the flood season has an upward trend under the two scenarios,but it is lower than the historical measured value,which is related to the decrease of the rainfall in the flood season in the next 30 years compared with the historical period.The simulated future runoff characteristic values showed that the peak value of the future flow rate occurs in August and September at most,but the peak current time of historical period mostly occurs in July and August,so the peak current time in the next 30 years will be delayed to a certain extent. |
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