Study On Design And Control Of Staged Drought Limit Water Level In Reserviors

As the global climate continuously warming,the regional aridification trend has become more and more serious,and drought disasters have become an important obstacle to the sustainable development of the economy and society.Therefore,scientific research on drought events and reasonable drought resistance is urgently needed.This paper aims to achieve the goal of drought relief and disaster reduction by utilizing the reservoir's capacity for storage.Aiming at the drought and water shortage caused by regional imbalance between supply and demand,Constructing socioeconomic drought indicators to assess the evolution of the drought situation in the basin;Tak,ing the main stream cascade reservoir project of the upper reaches of the Yellow River as the regulation target,the optimal segmentation method is used to stage the drought period of the river basin;According to the design concept of the drought limit water level and the theoretical construction of the control model,establishing drought-resistant optimal scheduling model for cascade reservoirs with the objective function of optimal transformation of drought level before and after reservoir optimization and control;Through the statistical analysis of the conversion of the drought level in different drought stages before and after the regulation of the reservoir,the control value of the staging drought limit water level of each reservoir is determined.The main research contents and conclusions are as follows:(1)Taking the Water Shortage Depth(WSD)as an indicator of socio-economic drought,the drought grade was evaluated on the monthly drought situation in the upper reaches of the Yellow River.The results showed that the drought in the b,asin was the lightest in the 1980s,and the drought was relatively in the 1990s and after the 2000.Severe;however,there is basically no drought in the flood season during the year,only mild drought and moderate drought occurred in a few periods,and the drought in the non-flood season,especially in January-April.(2)Considering the effects of precipitation,runoff,potential evaporation and water level on drought,the Fisher's optimal segmentation method is used to divide the drought period of the reservoir,and the results of the drought staging are determined as follows:Longyangxia is divided into July-August,September-October,January-March,April-June;Liujiaxia is divided into July-August,September-October,January-February,and March-June.(3)Aiming at drought and disaster mitigation,the design concept of staging drought limit water level based on cascaded reservoir combined drought-resistant optimal dispatching is discussed,and the theory of the drought evaluation module and the obj ective function module of the two control modules in the drought resistance model was carried out according to the design concept.Finally,the maximum drought degree of conversion and the drought grade of conversions is the obj ective function when the drought level in the staging period before and after the reservoir regulation are in the optimal direction,and build a cascade reservoir model of drought-resistant optimization scheduling.(4)After the implementation of drought-resistant dispatching,the results of drought assessment of the drought level in the drought period before and after the regulation of the reservoir are statistically analyzed.The results show that:Compared with before,there were some periods of destruction in the July-August after the reservoir regulation,and moderate and above drought events occurred,but the frequency of occurrence was small,the maximum was 7.5%;all dry periods in September-October were converted to drought-free;the moderate and above drought events from November-March were converted into mild drought and drought-free conditions,of which the proportion of drought-free period was 52.5%,an increase of 40%;in the April-June period,the drought-free period increased by 37.5%,and the mild drought and above drought periods decreased significantly,especially moderate drought period was reduced by 22.5%.In summary,the drought conditions in the basin after the regulation of the reservoir have been alleviated to a large extent,and the combined drought control effect of the cascade reservoirs is significant.(5)Before and after the regulation of the reservoir,the statistical analysis of the long-term changes in the degree of transformation and the grade of conversions in the drought-free period and the other four grades of drought during the different drought period.According to the optimal steps of the drought limit water level and the revised principle,the drought limit water level of each reservoir is determined.