Study On Eco-Environmental Water Requirement For Hanjiang Upstream Basin

Hanjiang upstream is regarded as the main water source for local eco-environment and society development, fetching water for Middle Route South-to-North Water Transfer Project, supplying water for Guanzhong region in Shaanxi. Increasing exploitation of water resources for planning cascade hydropower reservoirs and water transfer project has great impacts on eco-environment of Hanjiang upstream basin, such as decline of local water environmental carrying capability, even unfavorable development of ecology system. To suit for era development, guarantee sustainable development of Hanjiang basin, develop in a perfect harmony with eco-environment and society economy, and develop society economy in a largest scale but not destroying human eco-environment, it is vital necessary to study water environmental carrying capability. However, the study on eco-environmental water requirement is one of important composing parts for the study on water environmental carrying capability. Thus it can be seen that the study on eco-environmental water requirement for Hanjiang upstream basin has great important realistic significance.This paper collects and carries through systemic analysis the several aspects data such as water resources, aquicolous ecology, water environment, hydrology, distribution of ecology vegetations, society economy development, basing on the theory of continuable development and layout of water resources.The model of calculation on eco-environmental water requirement for Hanjiang upstream basin is set up.Then the amounts of eco-environmental water requirements of inner and outer riverway are worked out.Thus the amounts of eco-environmental water requirements are ascertained about varied transects, months and the whole basin in the varied hydrology frequency years. At last, the society water demand is calculated, and the static amount of water transfer isobtained by analyzing water resources equilibrium of Hanjiang upstream basin. So the basic data for the study on water environmental carrying capability for Hanjiang upstream basin are offered through the study on eco-environmental water requirements. The paper can provide referenced suggestions for decision-making of the local government.The main conclusions of this paper are as follows:(1)The model of calculation on eco-environmental water requirement for river basin is set up, which has two parts of the model of calculation for inner and outer of riverway. The eco-environmental water requirement of inner riverway is composed of basic flow of riverway maintaining the water environment, transpiration of water surface, water requirement for shipping, seepage, transporting sand and contamination cleaning. And that of outer riverway is composed of water requirement for varied ecological vegetations.(2)The eco-environmental water requirements of Hanjiang upstream basin are ascertained in the 4 hydrology frequency years of 20ï¼…, 50ï¼…, 75ï¼…, 95ï¼…, which are 70.68*108m3, 83.34*108m3, 62.10*108m3, 93.42*108m3 respectively. The eco-environmental water requirements of basin in the 4 hydrology frequency years account for 35% or so of the run-off in the corresponding year.(3)The water resources equilibrium of Hanjiang upstream basin is analyzed by the example of the lower water year 1995. The society water demand forecast is 24.30*108m3 . Without regard to the impact of water transfer on eco-environment, the water transfer to outer is 8.6*108m3. 74% of the total water resource is eco-environmental water requirement, and 19% of that is society water demand. So the degree of exploitation of water resource in the Hanjiang upstream basin is rather low, and the potential of exploitation is much great.