Ecosystem health assessment of the Dishui Lake in Lingang New Town, Shanghai

To make a scientific comprehensive diagnosis of the ecosystem health situation of the Dihsui Lake, the center of water control in Lingang New Town, the surface water and sediment samples of the Dishui Lake as well as ecological characteristics and social economy situation were used to select the minimum data set of ecosystem health assessment. According to the characteristic of each indicator and analytic hierarchy process (AHP), an appropriate scoring standard and weight can be determined, which is necessary to make an evaluation of the Dishui Lake ecosystem health situation. The study showed that totally fifteen indicators from three aspects, including DO, TP of surface water, TOC, TP, Hg, As, Cu, Zn of sediments, Chl-a, Ex, Ex_st, population density, the amount of annual tourists and the percentage of green coverage, were selected into the MDS. The results of evaluation indicated that the ecosystem health indexes of the Dishui Lake in winter (2012), spring and summer (2013) was 0.76, 0.71 and 0.69 respectively, which showed that the lake was in the stable “ less healthy level”. This consequence was similar to the fact that the lake was in the situation of mild eutrophication in recent years and revealed that the key restrictions of the Dishui Lake are TP, BA and Ex_st. Therefore, it is necessary to control the exogenetic P discharged into the lake to improve the water quality of upstream runoff and to increase the amount of plankton in order to make the structural eco-energy better.