On the changes of water quality in Jihongtan Reservoir in the past decade and the way for its evaluation
LIU Hao1,WANG Shan-ju2,LIU Yu-hua2,GUO Hong2(1 Qingdao Branch of Management Bureau of Water Diversion from the Yellow River into Qingdao of Shandong Province,Qingdao 266110,Shandong,China;2 Jihongtan Management Section of Management Bureau of Water Diversion from the Yellow River into Qingdao of Shandong Province,Qingdao 266110,Shandong,China)
The present article is concerned with the changes of water quality in Jihongtan Reservoir during the past decade(1997—2006) and the change evaluation with a particular analysis of the water content of TN,TP,and CODMn.The results of our evaluation show that the content of TN is higher in winter and spring than in summer and autumn.However,there is no significant change with that of TP and CODMn.On the contrary to the content of TN,the content of phytoplankton proves lower in winter and spring but higher in summer and autumn.The mass composition of the phytoplankton turns to be dominated by diatoms and cryptophytes in winter and spring while it is by green alga and cyanobacterias in summer and autumn,with the exception in 2006,when it was dominated by green alga against cyanobacterias in summer and autumn.As a result of the exception,the water quality turns to be better than in 2004 and 2005.Thus,it can be said that the annual average content of TN turned higher in 2003 and 2004 though with no obvious changes were found in other years.On the other hand,the analysis of the annual mean content of TP and CODMn didn't show obvious change during the same period. As to the annual mean cell density of phytoplankton,it proved higher in the period from 2003 to 2006,but lower in the rest of years,with some drop in 2006. However,the mass composition of the phytoplankton proved to be dominated by diatoms and cryptophytes from 1997 to 2002,but by cyanobacterias from 2003 to 2005 and by diatoms and green alga in 2006.The above analyses and evaluations by means of Nemero Index help us to conclude that the water quality of the reservoir can so far be categorized into Level II according to the state water quality standard with the trophic state of the reservoir being at the mesotrophic level.Therefore,the general situation of the water quality of the reservoir can be said well-conserved in the past decade,though the trophic level once tended to get deteriorated in 2002.Particular improvement was seen in 2006,which proved that the water of the reservoir can be used for drinking and farming safely and securely.
【CateGory Index】： X524