Evaluation of river eutrophication of the Haihe River Basin

Based on the data of surface water quality in 2009,river eutrophication level of Haihe River Basin was evaluated by using the main rivers' eutrophication potential and index of phytoplankton. The results showed that all the tested rivers of the Haihe River Basin had a relatively high nutrient content,and the average concentration of total nitrogen( TN) and ammonia( NH3-N) were 8. 13 and 4. 34 mg·L- 1,respectively,which were 2 times higher than those of the surface water quality standard of class Ⅴ( GB3838—2002). The average concentraton of total phosphorus( TP) was 0. 87mg·L- 1,which was also over 2 times higher than the water quality standard class Ⅴ( 0. 4 mg·L- 1for TP). All the average TP concentrations in the North Canal,Chaobai River and Jiyun River,Ziya River and Heilonggang River System exceeded 1 mg·L- 1. In the spatial scale,most of the eutrophication rivers were located in the middle plain area of the Haihe River Basin. The eutrophication potential in these rivers indicated that only 3%were in oligotrophic or moderate erutrophication state,while 44% were in severe eutrophication,most of which were distributed in Beisan,Ziya and Zhangwei River System. Thus both of the oxygen consumption and nutrients mitigation should be taken into consideration for water pollution control to improve the river water quality of the whole basin.