Comprehensive Assessment Of Ecological Security For Lakes And Reservoirs

Reservoirs play a significant role in regional economic and social development. There are more than140large and medium-sized reservoirs in Zhejiang Province, which undertake the tasks of water supply for most cities. In recent years, water bloom disasters occurred frequently in some reservoirs, which brought serious security threats to the water utilization, especially to the safety of drinking water. Based on the investigation of ecological status for the six important reservoirs in Zhejiang Province, the social-economic impact to the reservoir ecosystem, the health of the aquatic ecosystem, ecosystem service and ecological disaster were assessed respectively in the paper. Moreover, a comprehensive evaluation of the ecological security was carried out on the basis of the above assessment results. The main research results are as follows:(1) Analytic hierarchy process (AHP) and the multiple fuzzy comprehensive model were adopted in the impact assessment of human activities to the ecosystem. The results showed that the comprehensive stress indexes for the six reservoirs were at the secondary level, the ecological structure was reasonable and the ecological system was stable to a certain extent.(2) A fuzzy synthetic assessment model based on entropy weight for ecological health of the reservoirs was set up, using the ecosystem structural and functional index. The results indicated that the average ecosystem health comprehensive index(EHCI) of each reservoir during2008-2011was ranged from high to low as follows:Hushanhu Reservoir> Tangpu Reservoir> Jiaokou-Zhougongzhai Reservoir> Changtan Reservoir> Shanxi Reservoir> Xin’anjiang Reservoir.(3) The state evaluation method and the economic evaluation method were integrated to analyze and compare the ecosystem service. Results demonstrated that the ecosystem service state index of the reservoirs was all above4.53and were categorized as well. The economic value of six reservoirs reached to4.11×1010Yuan/a, among which the direct value was2.02×1010Yuan/a and the indirect value was 2,09×1010Yuan/a. The average ecosystem service value per unit area of the reservoirs was58.22Yuan/(m2-a).(4) Ecological disaster degree was assessed by comprehensive index method. Results showed that Changtan Reservoir suffered slight disaster, Shanxi Reservoir suffered moderate disaster in2009. Xin’anjiang Reservoir and Tangpu Reservoir were subjected to moderate disaster in2010. Hushanhu Reservoir had no disaster in2010. And there was no algae bloom in Jiaokou-Zhougongzhai Reservoir in recent years.(5) Comprehensive evaluation of ecological security was carried out by DPSIR conceptual model on the basis of the above results. Final results indicated that the ecological security of reservoirs were usually at the medium safety level, only the Hushanhu Reservoir reached to the safety level in2008and2011.On the whole, the ecological security of the reservoirs is trending downward.