Research On The Streamflow Change And The Distinction Of Hydrological Drought In Luanhe River Basin

With the double effects of climate change and human activities,water resources shortage and extreme hydrological events occur frequently,and always limit the development of the social economy.Therefore,for reasonable water management and social development,the trend of streamflow and the feature of hydrological drought in Luanhe River Basin are studied in the paper.Luanhe river basin is one of the four first order zoning areas of Haihe river basin,which is one of the most important water resources areas of Tianjin and Tangshan city,and it is one of the places where drought always occurs.Therefore,the paper was based on the long term observed meteorological and hydrological data to analyze the change of hydrological and meteorological elements,then to decide the trend and phase of runoff.Also,the SWAT model,the Budyko decomposition method and geometric approach were employed to quantifying climate change and human activities on mean annual runoff in Luanhe river basin.Besides,Using the SWAT hydrological model,we proposed a way to distinguish the drought with water scarcity of the hydrological system.The study could provide significant reference for water management scientifically and reasonably,then making better plans for drought.The main results and contents are as follows:(1)The variation of hydrometer factors were studied by five years sliding average and Mann-Kendall method.The sliding T test and order cluster analysis were used to test the change point of runoff time series,combined with the actual underlying surface change.The results show that the 1979 is the change point of runoff time series in Luanhe River Basin.Then the long-term period can be divided into two periods: the reference period ranged from 1957~1979 as the undisturbed period,and the impaired period was from 1980-2010 as the disturbed period.(2)The SWAT model was calibrated and validated in undisturbed period in the five sub-watersheds of Luanhe River Basin,and the model was of good accuracy to simulate the runoff series.Among them,R2 and Ens of the calibration period in Liying hydrological station are 0.76 and 0.76,respectively.In Chengde hydrological station,the R2 and Ens of the validation period are 0.82 and 0.83,respectively.(3)The Budyko decomposition method,geometrical approach and SWAT model were employed in the study of quantifying the climate-and human-induced runoffdecrease.Based on the Budyko decomposition method,the average impact of climate variation accounted for 25.0% of the runoff decrease,and the contribution of human activities ranged from 74.9%.Using the geometrical approach,the climate impacts were 24.7%,and the contribution of human activities were 75.3%.Based on SWAT model,the climate variation accounted for 63.8%,and the human impacts were about36.2% for average.(4)Based on the method of quantifying the drought and water scarcity,we make a distinction between the watershed drought,watershed water scarcity and streamflow water scarcity in Luanhe river basin.The result shows that the water deficit caused by watershed drought was the largest among the three phenomena,and it was about twice as great as water deficit caused by streamflow water scarcity in the selected sub-watersheds.