The Research Of Instream Environmental Water Requirement In Huaihe River System

China's Huaihe River valley is in a serious shortage of water resources and also is serious polluted. This not only threatens the water supply security but also caused a serious impact on the ecosystems and the river health. Therefore it is necessary to study the environmental water requirements of Huaihe River.Based on the eco-system analysis, this research would calculate the minimum and appropriate environmental water of the important reaches and lakes of Huaihe River System with Hydrologic Index Methods and Hydraulic Methods. Combined with the Multi-Criteria Water Distribution Model it would put forward feasible environmental water in various level years by balancing economic and social development and ecological protection requirements.This paper first analyzes connotation of the environmental water requirements. The environmental water requirements have both social and natural property. Its social property coordinates the Environmental water requirements and the social-economic needs and its natural property presents as time, space, threshold and quality. The theory study and the application of the calculation method of environmental water requirements at home and abroad proves that the Hydrology Index Method would be more suitable for the calculation of environmental water requirements at the basin level.Base on the ecological research and the analysis and evaluation of Huaihe River's aquatic ecosystem the study divides the basins into 3 categories. And according to the various characteristics of these 3 categories different ecological protection targets are set up. The Environmental water requirements include the minimum requirements which could maintain the status quo and appropriate requirements which would maintain the stability of the ecosystems. The research uses the Tennant Method to calculate the Environmental water requirements in each reach and checks the results of important sites with Hydraulic Method and proposes the Environmental water of Huaihe River System in the planning level. It also uses the Hydrological Method ,Curve-Correlation Method and Minimum Biological Space Analysis Method to calculate the Environmental water level of five important Lakes.At the end the paper introduces a Multi-Criteria Water Distribution Model which quantifies 4 basic principles of basic life water protection, the lowest protection for appropriate Environmental water, the lowest socio-economic water protection, the principle of fairness(which includes occupied priority, area priority and the population priority) and efficiency. Then the suppliable water in different level years would be divided between six third-level regions so it can calculate the satisfied degree of Environmental water in each region. It could also put forward feasible environmental water in various level years by balancing economic and social development and ecological protection requirements. The results show that in 2010, 2020, 2030, the Environmental water available are 11.2%, 12.3% and 15.1% of the total water resources. The results can be used as the basis of ecological scheduling.