Integrated evaluation of water quality and quantity of the Wei River reach in Shaanxi Province

The water environment condition of the Wei River reach in Shaaxi province was analysed in terms of the water quality, water quantity and the integrated results of the water quality and quantity, based on the data collected over the period from 2000 to 2008. Moreover, the correlation between the runoff and the concentrations of COD and NH₃-N at the main hydrological stations in the Wei River reach was discussed. The conclusions can be drawn from the results. (1)The middle and lower stream of the Wei River reach in Shaanxi province has already been polluted. The concentrations of COD, NH₃-N BOD₅ and DO exceed the national surface water quality standards from the Xingping control section to the Tongguan control section. (2) The average runoff of the Wei River amounts to 51.91×108 m³, which equals to 70 percent of the average annual runoff volume of the Wei River over the period from 1959 to 2008. The available water resource descends in terms of the runoff volume of the Wei River reach. The scarcity of water resource resulting from the water quality problems has been more and more severe in the region. (3) The concentrations of COD, NH₃-N correlates to the runoff weakly in the upstream of the Wei River, while the average negative correlation between the pollutant concentrations and runoff is shown in middle and lower stream of the Wei River. Compared to COD, NH₃-N correlates to the runoff the Wei River more apparently.