Hydrological Risk Assessment And Regulation Of Inter-Basin Water Transfer Project

This study takes the Han River to Wei River Water Transfer Project(HWWTP)as an example,and considers the impact of the changing environment to conduct a systematic statistical analysis of the water source area(WSA),the water receiving area(WRA)and the downstream impacted area(DIA)of the cross-basin water transfer project.(Most)unfavorable conditions,explore the scheduling process of the(most)unfavorable conditions of the water transfer project,and propose a scheduling plan for the most unfavorable conditions of the water transfer project.The results are as follows:(1)Runoff evolution law of WSA,WRA and DIAThe results show that the runoff series in the WSA,the WRA and the DIA of the HWWTP are uneven in annual,inter-annual and inter-generational distribution.By regional synthesis of the hydrological statistical characteristics of runoff series in three hydrological areas,the representative annual runoff data of the three hydrological areas are obtained.According to the analysis of the runoff process chart,the annual runoff series of the WSA,the WRA and the DIA all showed a downward trend,and the fluctuation of runoff was different in different years.However,the annual runoff of the three hydrological areas all increased sharply after the 1980 s.(2)The optimal hydrological frequency model for WSA,WRA and DIAAccording to the analysis and test results,the annual runoff series in each hydrological area had a significant downward trend,and the annual runoff series in the WSA and the WRA had a mutation in 1990,and the annual runoff series in the DIA had a mutation in 1985,which showed an obvious ‘inconsistency’ characteristic.Therefore,the hydrological frequency analysis method based on stationarity hypothesis is no longer applicable to this project.Therefore,the GAMLSS model is proposed to construct a non-consistent hydrological frequency model for the annual runoff series in the WSA,the WRA and the DIA.The results of goodness of fit test show that the optimal distribution of the annual runoff series in the three hydrological areas is lognormal distribution,where the location parameters change with time and the scale parameters do not change with time.(3)The(most)unfavorable conditions of the inter-basin water transfer projectThe non-consistent hydrological frequency models of the three hydrological areas were taken as the optimal marginal distribution of the runoff series of the three hydrological areas.The two-dimensional joint distribution of the two pairs of the three hydrological areas and the three-dimensional joint distribution of the three hydrological areas were constructed by the Copula function,and the abundance and decline encountered analysis was carried out.According to the calculation results,the favorable probability of water transfer is 40.93%and the unfavorable probability is 59.07% in the combination of three hydrological areas with three-dimensional joint distribution,that is,the situation of the same drought of three hydrological areas occurs once every 2 years.When the WSA is a dry year,the conditional probability of simultaneous dry water occurrence in the receiving area and the DIA is 45.27%.It can be seen that the adverse probability of water transfer from Hanji-Weihe River Diversion Project is obviously greater than the favorable probability,and the adverse annual return period of water transfer is very short,which is very unfavorable to the inter-basin water transfer management during the operation period.In addition,when the WSA is a dry year,the amount of water that can be transferred from the inter-basin water transfer project is less,especially in extreme cases,and the planned scale of water transfer is difficult to be guaranteed,which may even affect the operation of the middle route of the South-North Water Transfer Project to a certain extent.Considering that when the WSA is a dry year,the probability of dry water in the WRA and the DIA is high and has a great influence on it,the dry time in the WSA is regarded as the unfavorable working condition of water transfer project operation,and the extreme dry year is regarded as the most unfavorable working condition.According to the analysis results of cumulative anomaly method,the period of dry water from 1964 to 1980 and 1990 to 2004 are selected as the unfavorable conditions for water transfer project.Combined with the nonconsistent hydrological frequency model of annual runoff in the WSA,1995(90% dry year),1999(95% dry year)and 1997(99% dry year)are selected as the most unfavorable operation conditions of the HWWTP.(4)Reservoir(group)dispatching process and engineering water replenishment effect under the most unfavorable working conditionsBased on the unfavorable working conditions and the most unfavorable working conditions of the HWWTP,the simulation scheduling research is carried out respectively.The results show that,under adverse working conditions,the average annual water transfer of the Hanji-Weihe River Diversion Project is 970 million m~3(1964-1980)and 934 million m~3(1990-2004)respectively,and the water supply guarantee rate is 35% and 13%,respectively.Therefore,it is difficult for the water transfer project to reach the multi-year average water transfer target of 1 billion m~3 under adverse working conditions,and the guarantee rate is low.At the same time,the study found that negative Huang Jinxia,three river hydropower station under the condition of average output are lower than design value for many years,and because of the adverse conditions Huang Jinxia reservoir’s water shortage,three river reservoir to control the brake of water increased,leading to Huang Jinxia hydropower station,power generation and energy with water is low and falling,However,the power generation and energy consumption of Sanhekou hydropower station have increased relatively.Under the most unfavorable conditions,the average annual water transfer volume in the three typical dry years of the water transfer project is 904 million m~3,which still falls short of the annual average scheduling target of 1 billion m~3.Under the influence of the dry water,the amount of water transferred from Huangjinxia Reservoir was reduced,and the water was mainly transferred from Sanhekou Reservoir to the control sluice,which played the role of Sanhekou Reservoir in regulating and storage for many years to a certain extent.In addition,the water transfer project scheduling and downstream impact tapping area before and after water change analysis shows that when more or less the same,although transferred water can relieve the tense situation of xi "an city of supply and demand,but there are more than 400 million m after the gap,if not in time to take emergency measures,will be in xi ’an water security situation caused a certain degree of influence.However,if the water demand in the DIA continues to increase in the future,there may also be some water safety problems,which should be paid close attention to.