Research Of Optimal Multiobjective Operation Of Reservoirs Based On Coordinating Water Supply And Demand

The fundamental realities of water resources in China is the uneveness of spatiotemporal distribution and the low level of per capita.The Nansi Lake(NL)consisting of upper lake and lower lake,where the per capita of water resources is less than 300 m~3,suffers from severe water scarcity.The agricultural water demand takes off the 80 percent of the total in NL basin.With rapid socioeconomic development and the accelerated urbanization,the industrial and domestic water demand have rigidly increased.As a consequence,optimizing basin crop planning to reduce regional water demand and putting forward corresponding operation plan of hydraulic engineering is the basic solution to ease the water scarcity of basin,which is the leading edge of research of basin water resources management.This paper builds an optimal crop and irrigation planning model based on the situation of basin agriculture.The optimal result of agricultural water demand is then used as the input of optimal water resource regulation model,and the overall water resource allocation and the regulation process of NL are determined.The main conclusion can be summarized as follow:(1)An optimal crop and irrigation planning model is built based on the theory of inadequate irrigation and the Penman-Monteith model.The decision variables are including planted area of each crop and irrigation water of each crop during different periods.The objective functions represent the maximum of total net agricultural output value and relative yield.The established model is constrained by agricultural acreage,agricultural water supply and water balance condition.(2)Using the optimal agricultural water demand as input,an optimal basin water resource allocation model is developed to determine the water deficit of basin water resource system and the optimal water resource allocation pattern.The basin water resources system is divided into several computing elements and the simulation rules of the order of water supply among multiple water resources and water users are determined.The water resource system is simulated by the establishment of state transition equations that simulates the transition of system water within every elements and among different elements.The objective function is minimizing the water deficit of water resource system and the constraint is the water supply less than water demand.(3)A bilateral supply-demand coordinated model of optimal reservoir regulation is built to obtain the regulation diagram of reservoirs.The rules of divisional water supply and water diversion is based on the importance of each users and the ability of reservoirs in diversion respectively.One of objective functions of model is minimizing the weighted sum of system water deficit and the amount of discarded water,the other is maximizing the coefficient of dispersion of water supply guarantee rate.The model is constrained by the indicator storage of water diversion and the indicator storage of water supply.The overall supply-demand coordinated model is developed through combining the agricultural model,water resources allocation model and the reservoir regulation model.(4)The Nansi Lake(NL)basin is chosen as the case study in this paper.The scenario of50 percent assurance rate shows that the net agricultural output value enhances 3.407 billion yuan,the saving irrigation water is 499 million m~3,water supply guarantee rate is improved by 25.55%;The scenario of 75 percent assurance rate shows that the net agricultural output increases 3.630 billion yuan,the saving irrigation water is 690 million m~3and water supply guarantee rate is improved by 29.88%.