Abstract: The water source of the middle line in the south-to- north water diversion is in Danjiangkou Reservoir waters. Its water quality reaches Ⅱ.Organic matter is the reservoir's main pollutant. The reservoir takes on the middle nutrient level. Measures of building eco-environment in the area are as follows: building eco-forest; planned complex management of waters; reforming the backward agricultural production on the base of eco-agriculture by the modern clean one and designing the productive area of eco-enviro...