Integrated evaluation of water quality and quantity in combination with eco-environmental water requirements for the Yellow River

River water has dual functions; it can be withdrawn from the river course for agricultural, industrial, and domestic uses and provides eco-environmental water for riverine systems. A concept of intensity of ecological function of river water has been put forward, and an integrated water quantity and quality evaluation method in combination with eco-environmental water requirements has been developed for a river. Based on the monthly data of water quality and quantity as well as the withdrawals, an integrated evaluation of water quantity and quality has been conducted for the Yellow River. The results indicate that the temporal and spatial variations of intensity of ecological function of river water were related to that of the water quantity and quality. The total water resources availabilities of the river were 371.17、425.50 and 500.64×10 8 m 3 in 1997, 1998 and 1999, respectively. The increments of water resources availabilities caused by providing eco-environmental water for the riverine systems were 129.51、151.51 and 205.88×10 8 m 3 in these three years, respectively. They were lower than the eco-environmental water requirements of the riverine ecosystems, leading to the intermittent interruption of river flow and other eco-environmental problems of the Yellow River.