ASSESSMENT OF ECOSYSTEM HEALTH IN THE RUXI RIVER BASIN OF ZHONGXIAN COUNTY IN THE THREE GORGES RESERVOIR AREA BASED ON PRESSURE-STATE-RESPONSE(PSR)MODEL

With the Pressure-State-Response(PSR)model developed by the Organization for Economic Cooperation and Development(OECD),this paper assessed the ecosystem health condition from 2005to 2009 in the Ruxi River basin of Zhongxian County in the Three Gorges Reservoir Area.Based on the researches about watershed ecosystem health assessment in both domestic and foreign countries,an integrative assessment model of ecosystem health in the Ruxi River basin was built.Three layers(object,item and index layers)were set up in the ecosystem health assessment index system.The weights of the nine indicators were estimated by Analytic Hierarchy Process(AHP),and integrative index model of watershed ecosystem health was used to determine the ecosystem health comprehensive index(E).The results showed that the mean value of Efrom 2005to 2009in the Ruxi River basin was 0.509 7,showing a state of middle health in these areas overall.During these years,there was a fluctuated trend in terms of the ecosystem health in this basin.In particular,the basin ecosystem was healthy in 2007when the Evalue was the highest among the five years,while the ecosystem was morbid in 2006.Moreover,the ecosystem health of Ruxi River basin in the Three Gorges Reservoir Area was greatly influenced by net primary productivity(NPP),population density,and surface water comprehensive pollution index.Basically,from 2005to 2009,the social,economic and natural environment of Ruxi River basin in Zhongxian County was in good condition,and the ecosystem was somewhat healthy and sustainable.However,a combination of ecological effects with social and economic effects on the watershed should be considered to maintain the ecosystem health in Ruxi River basin of Zhongxian County.