Research On Ecological Flow And Operation Of Nierji Reservoir

In recent years,the ecological problems of the reservoir have become the focus of research.The Nierji reservoir is a large-scale control project that undertakes the tasks of flood control,water supply and power generation,as well as overalls improvement of downstream shipping and aquatic ecological environment,and creates conditions for the optimal allocation of water resources in the Songliao basin.The construction of the reservoir will have an impact on the original river shape of the Nenjiang River,changing the hydrological characteristics of the basin,such as river shape and other hydrological indicators.In order to reduce the da mage of Nenjiang basin ecosystem caused by the operation of Nierji reservoir and to discuss the influence of hydrologic variation on the ecological regulation of ecological flow,a reservoir ecological regulation model was established and an effective ecological regulation scheme was developed in this paper.The main research contents and conclusions are as follows:(1)The Hurst coefficient method and process line method were used to complete the hydrological variation points,by using Mann-kendall mutation analysis method,Moving T method,and Sequential clustering method to examine mutation point and combining the theory of serial number summation and Spearman correlation coefficient calculation of hydrological time series as a comprehensive identification,the year of hydrological variation of the reservoir was determined to be 1963 and 1999.Considering human disturbance as the main driving source of hydrologic variation,the natural state,sub-natural state and present hydrologic sequence were divided.(2)The NGPRP method,monthly frequency distribution method and monthly maximum ecological runoff method were used and to reduce the time scale,the annual scheduling period was divided into non-icebound period(April-October)and icebound period(November-March).The time scale of non-icebound period was refined to ten days,and the time scale of icebound period was month.The minimum ecological flow rate,the optimum ecological flow rate and the maximum ecological flow rate under the conditions of natural state,sub-natural state,present state and without considering the hydrological variation were calculated respe ctively.According to the evaluation results of Tennant method,it is found that the degradation of the reservoir ecosystem is mainly affected by human disturbance.Observing the ecological flow process in the sub-natural state and without considering the mutation state,it is found that the difference between the minimum ecological flow rate and the average flow rate for many years was 9.21% and 1.70%,the percentage of suitable ecological flow in the average flow for many years differed by 3.04% and 1.47%.It showed that the study should consider more the natural ecologicalrunoff process.The minimum ecological flow value is small,the ecological satisfaction degree is low,and there is no obvious trend of change.Therefore,it is not suitable to be used a s a reference index for a long time.The value of the suitable ecological flow is similar to the average value of the multi-year runoff in the same period,and the overall change trend of the two is basically the same,which meets the ecological water demand of the region.The maximum ecological flow changes drastically and cannot fully meet water demand.It is recommended as the maximum ecological flow limit.(3)A model for the ecological operation of Nierji reservoir was established with the maximum power generation as the goal and multiple ecological flows as the constraints under the hydrological variation condition,and the ecological operation of the reservoir under the hydrological variation condition was improved.The optimal artificial fish swarm a lgorithm was used to solve the operation results of five typical years with different ecological constraints.The results show : Considering the ecological regulation of hydrologic variation,it is necessary to reduce the ecological target to protect the riv er ecosystem to the greatest extent in the years of water deficit.The contradiction between the goal of reservoir power generation and the goal of ecological use is particularly prominent in the dry season,and the contradiction can be alleviated effectively in the year of abundant and abundant water.For power generation tasks and sufficient water,it is recommended to choose a scheduling scheme that meets natural ecological runoff.For water shortages,it is recommended to choose a scheduling scheme that meets current runoff.For water storage tasks,it is recommended to choose a scheduling scheme that meets current ecological runoff.For water supply tasks,it is recommended to choose the scheduling scheme with the largest amount of diarrhea in different years.This article provides decision makers with a variety of ecological scheduling solutions,it can provide reference and technical support for reservoir operation in the future.