Risk Assessment On Eco-environmental Influence In Water Diversion Areas Of The South-to-north Water Diversion Project Along The Western Line

First stage construction of the south-to-north water diversion project along the western line mitigated the fact of water resource shortage and improve ecology environment in north-west region of the country. In the mean time,it affected the ecological environment in diversion area,particularly the ecological environment system beside the river which lies in the downstream of the diversion project would be affected first by the diversion. The paper identified the minimum co-environmental water demand based on the local natural condition and ecological environment. According to the result,it did research about risk estimation of runoff regulation process affecting ecological environment. The main research content and the results are as follows:(1) The paper presented the concept of eco-environmental water demand, characteristic and the background of bringing forward it,also,it did some research on the development in the field around the world,pointing out the shortage about the development in our country. It introduced the concept of risk,narrated the method of single risk analysis,and indicated the meaning of river ecological environment risk analysis.(2) The paper studied on the method of eco-environmental water demand around the world,stressing on the advantage,disadvantage and suited condition of different method.based on the data of monthly runoff,it used Person typeâ…¢distribution method to analyze annual runoff data of five dam site,adopting 7Q10 method,mimun monthly average discharge method,Tennant method to calculate the eco-environmental water demand in five rivers.(3) Using the principle of water amount balance to analyse the water consume of industy,agriculture,the loss of evaporation and seepage,and the diversion under design assurance rate,the paper calculate the amount of water it can discharge every year. It choosed the low-limited eco-environmental water demand which is deduced by the method of the minimum annual average runoff to control the amount of discharge,considered about over year runoff regulation,got the detailed discharge after diversion. (4) According to the selected risk calculation method,the paper estimated the degree of risk for ecological environment in diversion river dam location: Adopt to a minimum leak time under monthly average rate of flow,the risk for Aan,Renda, Yaertang and Keke is zero,Shangduke is 2.56%;Adopt to leak time under consulting rate of flow,every damsite risk is 0 without exception. For five rivers in the first stage construction of the south-to-north water diversion project along the western line,the diversion river'ecological environment would not be affected by diversion through risk evaluation.