Study On Ecological Water Requirement And Allocation Scheme Of Rivers And Lakes In Tianjin

With the acceleration of urbanism,water environment in the urban is becoming worse and worse.It is a new challenge for the environmental managers to manage and protect the urban water environment effectively.This paper provides a study on ecological water requirement and allocation of rivers and lakes in Tianjin.Based on the river system,urban water supply system and present situation of ecological water environment in Tianjin,a calculation method was established to calculate the ecological water requirement of rivers and reservoirs.Also this paper carried out allocation of ecological water demand and put forward a set of ecological protection schemes based on ecological divisions.The study has great significance to optimum allocation of water resources and management of water environment.The main research work and achievements are as follows(1)Based on a great deal of literatures about ecological water requirements in the domestic and oversea,the concept,research category,composition,and calculation methods of ecological water requirements were studied comprehensively.Considering the status of water eco-environment and development of water resources in Tianjin,the method of Tennant,hydraulic retention time and channel storage volume calculation were used to estimate ecological water demand of typical stations,self-purification water demand and evaporation and seepage loss in rivers and reservoirs,respectively.According to the above calculation results,it is concluded that the ecological water quantity in Tianjin is composed of two parts:river and wetland.Ecological water volume of the river is 872 million m~3,that of the wetland is 464million m~3(including the disposable replenishment of 206 million m~3),and the total planned ecological water volume is 1336 million m~3.(2)Through the ecological water requirement satisfaction evaluation,River ecological base flow satisfaction rate reached“excellent”,“good”,“average”and“poor”,accounted for 29%,6%,6%and 53%of the total number of rivers respectively.The ecological levels of four reservoirs were in poor state,and that of two reservoirs were in bad state.(3)On basis of ecological water requirements calculation,the connotation,dominating tasks and principle of the ecological water requirements allocation for improving water environment were analyzed,and the allocation mode of ecological water requirements was established.According to the characteristics of ecological water,its allocation should make full use of the flood season water flow as the outward channel diversion,coordinate the spatial allocation of ecological water,and utilize the function of hydraulic engineering system to guarantee the fluidity and continuity of water.The ecological water allocation in Tianjin mainly rely on rain flood,reclaimed municipal wastewater,Luan River water as well as divert water from Eastern route of South-to-north water Transfers timely to solve the rivers and reservoirs ecological water.