Research on the water environmental features and environmental capacity of Enshi river reach of Qingjiang river

Based on the five years´ (2003-2007 ) monitoring data of two water quality monitoring sections at the upstream and downstream of Enshi river reach of Qingjiang river, the water quality status was analyzed and the water environmental capacity was calculated. The results show that at the upstream section, Ammonia nitrogen and Contain fecal coliform are overweight, and water environmental status of this section presents mild eutrophication. At the downstream section, Total nitrogen is continued overweight, and total phosphorus, Ammonia nitrogen and Fecal coliform are only overweight in some years. Also, some heavy metals and volatile phenol, cyanide have been detected in the downstream section. However, this section doesn´t present obvious eutrophication. Analysis on the environmental capacity indicates that there is no carrying capacity for Ammonia nitrogen at Enshi river reach. But for other pollutants, the carrying capacities are still large. The carrying capacity of low waterflow period is only one-tenth of that of the flood period, so low waterflow period is the key period of the sewage treatment of Enshi city.