Research On The Influence Of Environmental Change On Drought Propagation In Luanhe River Basin

With the impact of climate change and human activities,the drought disaster is more increasingly prominent in a changing environment.Due to the impact of environmental change,the global hydrological cycle system and regional hydrological regimes may change,which affected propagation of drought in basin.Taking Luanhe River Basin,which is more significantly affected by human activities,as an example,the paper analyzed the characteristics of drought and the propagation of drought under the natural state.Meantime this paper analyzed the drought events based on the measured data and quantified the impact of runoff regulation and water supply of reservoir on the propagation of drought by comparing the propagation mechanism of drought,and then providing scientific ideas and technical support for the research on the propagation of drought under the environmental change.The main research contents and achievements of the paper are as follows:?1?Construction of Luanhe River Basin hydrological model.Based on the long-term measured hydro-meteorological data of basin,a SWAT was used to construct the hydrological model of Luanxian Station control basin.The results of hydrological model parameter calibration and validation showed that the runoff simulated values are prettily fitting to the measured values and the model is suitable for hydrological simulation in Luanhe River Basin.?2?Identification about the basin characteristics of drought.According to the data of soil moisture and runoff simulated by the hydrological model and the measured data of precipitation and runoff,the varible threshold level was used to identify the drought events and analyze the basin characteristics of drought under natural state and actual state.The changing environment with a decrease in the number of hydrological droughts and an increase in the average duration of droughts and deficiencies led to the intensity of drought became further worse.?3?Analysis on the basin characteristics of drought propagation under natural State.Based on the various types of drought characteristic variables,firstly,by comparing the beginning time of various types of drought,three types of drought propagation pattern were found in the luanhe basin,respectively,namely M-A/M-H,NM-A/NM-H and M.Secondly,according to the drought beginning time and the termination,the basin MAH events were selected to compare the lag time of drought propagation.Finally,including E,DS_M,SD and PD₁₀,four driven factors were selected.Based on the correlation analysis between hydrological?agricultural?drought and driven factors,the multiple regression equation of drought propagation was established,and the reasons for the occurrence of the three types of drought propagation pettern are explained.?4?Analysis of the influence of reservoirs,runoff regulated and water supplied by reservoirs,on the drought propagation process.Due to the reservoir regulation of runoff,most of the meteorological drought events did not propagate into hydrological drought,while meteorological drought events,which propagate into hydrological drought,have become even worse.Under the impact of reservoirs,the hydrological drought starting time averaged lagging time meteorological drought time decreased by2.4 days,and the termination averaged lagging time meteorological drought increased by 55.6 days.The regression equation of hydrological drought is no longer suitable for the reservoirs under natural state.Therefore,a RFD factor is proposed to characterize the impact of reservoirs.The regression equation for drought propagation process under the influence of reservoirs was reestablished,and the main factor RFD affecting the propagation of drought under the changing environment was determined.