Water Resource Value Evaluation And Operation Of Reservoir Based On Emergy

Water resources management is facing enormous challenges due to the impacts of climate change,rapid economic and social development,globalization and urbanization.One of those challenges is to emphasize the ecological service function of water,to highlight the comprehensive role of water resources in the economic,social and ecological environment,to balance the water demand of economic,social and ecological environment,and to maximize the comprehensive benefits of water resources.However,whether it is traditional multi-objective reservoir operation or reservoir ecological operation which has been rising in recent years,its objective is measured by physical quantity(such as water supply/power generation),or by monetary quantity,and then studied under the framework of multi-or single-objective decision-making.This paper attempts to introduce emergy theory and method into water resources dispatching management,using solar energy value as a measure to quantify the effects of water resources development and utilization,then constructing and solving the evaluation and dispatching model of reservoir water resources value based on emergy.From the view of energy value,this paper analyses and evaluates the changes of comprehensive value of water resources brought about by reservoir construction and operation,so as to provide a scientific basis for finding the optimal strategy of water resources dispatching and management.Some meaningful research results have been summarized this paper.The main contents and achievements of this paper are as follows:(1)Focusing on the evaluation of reservoir water resources value and reservoir operation,this paper systematically summarizes the research trends of evaluation methods of water resources value,especially emergy method,reviews the research progress of reservoir optimal operation,points out the new development of reservoir ecological dispatching and the shortcomings of current research based on the construction of ecological objectives.Combining with the service function and dispatching requirement of Danjiangkou Reservoir,the research content of this paper is put forward.(2)The calculation methods of emergy transformity of natural water and engineering water are summarized.Aiming at the difficulty of energy investment allocation in the calculation of emergy transformity of multi-output system of comprehensive utilization reservoir,a stage-by-stage method is proposed,which includes the calculation of emergy transformity of reservoir water body and the rate of output.Based on the principle of water balance and energy conservation,a model for calculating the emergy transformity of complex rivers under the action of reservoir storage,artificial water intake and water diversion is established.Taking the middle and lower reaches of the Hanjiang River in 2015 as an example,we calculate the emergy transformity of Danjiangkou Reservoir is1.56×10¹¹sej/m³,the emergy transformity of the middle route of South-to-North Water Transfer Project is3.96×10¹²sej/m³(represented by Beijing),and the emergy transformity of the main stream water below Danjiangkou Reservoir is 2.52×10¹¹sej/m³(the lower section of Gao Shi Bei).The results show the emergy transformity of the middle and lower reaches of the Hanjiang River is significantly affected by the influx of tributaries,water intake and diversion projects,reservoir storage and other factors.The emergy transformity of engineering water has spatial difference.(3)According to the input-output analysis of regional industrial,agricultural and domestic water use systems,the energy value of water resources,defined as the ratio of input energy value of water resources to total input energy value multiplied by output value,is developed.Based on the input emergy analysis of industrial,agricultural and living systems,the calculation method of the contribution rate of water resources emergy is put forward.According to the characteristics of multi-source water supply in regional eco-economic system,the proportion of reservoir water resources is further separated from the contribution rate of water resources emergy.On the basis of that,the calculation model of reservoir water resources value based on the energy contribution rate of reservoir water resources is constructed.Taking Danjiangkou Reservoir in 2015 as an example,we calculate the water resources value of Danjiangkou Reservoir in the middle and lower reaches of Hanjiang River,the water resources value of Danjiangkou Reservoir in the receiving area of the Middle Route Project of South-to-North Water Transfer and the hydroelectric power value of Danjiangkou Reservoir are calculated.The results show that the water resources value of Danjiangkou Reservoir in 2015 is 2.73×10²²sej,in which the middle and lower reaches of the Hanjiang River account for the majority,and the water receiving area of the middle route project accounts for a small proportion,which is related to the water transferring from the north only 23×10⁸m³ in that year;from classification,the water resources value of the reservoir in the agricultural system is the largest,accounting for 46.9%of the total water resources value of the reservoir,industrial system accounted for 29.7%,life and hydroelectric power system accounted for 9.4%and 8.6%,ecosystem accounted for 4.8%,and shipping accounted for only 0.7%.(4)Based on the generalization of the water resources system in the middle and lower reaches of the Hanjiang River with Danjiangkou Reservoir as the center,a multi-objective reservoir value operation model with the maximum value in the middle and lower reaches of the Hanjiang River and the maximum value in the receiving area of the Middle Route Project of South-to-North Water Transfer is constructed,and the value is measured by energy value and currency respectively.The model is solved by multi-objective genetic algorithm NSGA-II,and the TOPSIS method is used to rank the non-inferior solution sets,from which the recommended scheme is obtained.In order to compare the results,a single-objective model of Danjiangkou Reservoir's value operation is established and solved,aiming at the sum of the value of the middle and lower reaches of the Hanjiang River and the value of the receiving area of the Middle Route of South-to-North Water Transfer Project.Taking 2015 as an example,the multi-objective and single-objective optimization calculation of Danjiangkou Reservoir's value operation is carried out.The results show that the water resources value of Danjiangkou Reservoir in 2015 is 3.09×10²²sej under the single-objective,and the sum of the two objectives of the proposed multi-objective scheme is 3.07×10²²sej,which is larger than the actual 2.73×10²²sej.It shows that optimization of reservoir dispatching model can achieve greater value.The multi-objective non-inferior solution also reveals the non-inferior relationship between the water resources value of reservoirs in the receiving area of the middle route project and the water resources value of reservoirs in the middle and lower reaches of the Hanjiang River.