Surface Water Quality of Beiyun Rivers Basin and the Analysis of Acting Factors for the Recent Ten Years

As the most important drainage system,the quality of the Beiyun rivers basin play a great role on the city's environment and the areas of down streams,the acting factors were analyzed by the monitoring data of surface water,statistical data of water resources and socioeconomy,monitoring data of municipal treated sewerage,during the year from 2001 to 2010.The results show that the water quality of every branch is very poor.It was found that organics of oxygen consumption and ammonia nitrogen are the most important pollutants.The water quality is better during high flow period than rainless period,and highly depends on the branch water quality of Liangshui river,Wenyu river and Tonghui river.The branch water quality once got better after 2006,however,the concentration of pollutant parameters stands static above standard V during the year from 2006 to 2010,and it is very difficult to make the surface water quality improved.Economic development and population explosion put a great pressure on the water environment,and result that water quality is hard to thoroughly improved.Lack of clean water is another factor in contribution to poor water quality,precipitation can reduce the water pollution but the pollution of non-pointed source of surface water runoff will arise,and to Beiyun river,the pollution is diluted by the precipitation.Water quality is improved by the ratio of sewage disposed,but further results depends on the ratio improving especially in suburb areas.