From June to December of 2006

five storm events and three base-flow events at the Lintong hydrologic station were monitored.The quality of raw and clarified water from the events was analyzed.Results indicate that concentrations of SS

NO2—N and NO3—N

as well as COD

total P(TP)

and total N(TN) of raw water during flood are higher than those of base flow.High values of COD

TP

and TN of raw water are related to natural humic substances in surface soil.Total N of clarified water is mainly made of dissolved nitrogen and total P is mainly made of particle phosphorus.COD TP and TN of raw water are closely related with SS.The mean concentration method was used to estimate the weighted mean concentration of non-point source pollution(NSP) for each element.The method of water quality and quantity correlation was used to establish the correlation equation between NSP load and surface runoff for each element.The calculated mean NSP concentration and the established correlation equation were then used to estimate NSP load at the Lintong hydrologic station on Weihe River from 1991 to 1999.The results from the two methods prove to be credible.