Abstract:  In order to resist salt water intrusion and meet the demand of increasing water consumption, Hangzhou City government plans to move the water intake from Shanhusha to upstream a site called Lishan. Whether the water quality of new water intake can reach quality standard has become the focus of public concerns. Firstly, this paper analyzed present water quality ； secondly, field data of hydrology and water quality of several stations in Qiantang River were validated with the 2-D mathematical model Mike21. Then concentration in programming pollution load was calculated. Furthermore, on the basis of analyzing the influence factors on water quality such as upstream runoff amount and upstream water quality, and downstream tide range and pollution load, the rationality of water intake at Lishan site was evaluated. From these studies, when upstream low flow meets downstream neap tide, the concentration of water quality index COD Mn is close to national second-class seawater standard (GB 3097-1997).In order to insure water quality, pollution load should be reduced. The factors influencing water quality, such as upstream runoff amount and upstream water quality, and downstream tide range and pollution load, significantly effect water quality.

Key words: water quality prediction, mathematical model, water intake