The Current Situation of the Water Quality and Its Assessment on Lianhuadang River System, Yixing

Lianhuadang River System, flowing down with the Wuxi Harbor River, is one of the most impor- tant inflow rivers of the West Taihu. Based on the standards of the water environment functional zoning, its water quality should meet the requirement of the Class-III surface water. In April 2014 (average season) and July (abundant season), the field investigation and sampling monitoring have been performed twice respectively in the Lianhuadang River System. The results show that: the contamination indexes in the water exceeding the standard of the Class-III surface water mainly are the permanganate index, the total phosphorus, the total nitrogen, the ammonia nitro- gen and the chlorophyll A, of which the contamination of the nitrogen and phosphorus exceed the standard seriously. Due to the influence of the increasing stream flow in abundant season, the wa- ter quality in July is slightly better than that in April. According to the survey, the main pollution sources in the water are the waste water of the concentrating livestock and poultry breeding, the coastwise rural domestic sewage, and part of the Agricultural Area Source Pollution . Adopting the single factor contamination index method, the WQI method (the comprehensive water quality identification index method) and the water self-purification ability evaluation method, the results of the current situation evaluation for the water environmental quality of the Lianhuadang Water System show that: most rivers of the Lianhuadang Water System are polluted seriously; the com- prehensive water quality identification category is ranged from Class V to inferior class V-stinking sewage; the water body has a certain self-purification ability, and the capacity of self-purification varies in different periods.