EUTROPHICATION AND WATER CHARACTERISTICS OF LARGE AND MEDIUM-SIZED RESERVOIRS IN HUBEI PROVINCE

The reservoirs play important roles in the city water supply,industrial water,aquaculture,agricultural irrigation,flood control and tourism landscape.In recent years,with the development of national economy and society,eutrophication of reservoirs has become a serious environmental problem which negatively affects the economic development around the reservoir areas.In order to understand the changes of water environment in reservoirs,we measured a set of water quality variables,such as water temperature,transparency,permanganate index,total nitrogen,total phosphorus,chlorophyll a content in 30 reservoirs of Hubei Province,China.The above reservoirs were sampled in March,June,July and October,2010.The monitoring result of water quality was evaluated with the Basic Analytical Methods of Environmental Quality Standards for surface water,and the nutrition state was evaluated with eutrophication index for lake and reservoir;the influence of some environmental factors on eutrophication was analyzed by factors cluster analysis,and some types of the reservoirs were established.The results showed that water qualities of 14 reservoirs were Grade Ⅱto Grade Ⅲ,8 reservoirs were Grade IV and 8 reservoirs were Grade Ⅴ;except for the water of Baiyunhu reservoir which was light eutrophication,water of the rest 29 reservoirs were in mesotrophication.The key factors for reservoir eutrophication were ammonia nitrogen and total phosphorus;the dissolved oxygen,total nitrogen,water temperature,permanganate index also contributed a lot for the eutrophication.Four types of the polluted reservoirs were clustered according to their source of pollutants,including industrial waste water pollution source,sewage source,agricultural non-point pollution sources and light pollution source of reservoir breeding.Based on their pollutants source,different suggestions were provided to decrease or prevent them from the pollution.