| Lake health assessment as the main means of diagnosis of lakes health level,the lakes ecosystem plays an important role in monitoring and management,this thesis constructs the assessment basin health assessment index system,science to explore health assessment method,put forward the proposal to the lake in the development of health assessment system,The health status of Juyan lake was evaluated.Taking Juyan lake as the research object,through sampling experiments,field investigations,visits and data collection,the health assessment of Juyan lake was carried out based on analytic hierarchy process(AHP)and step by step weighting method.The specific research results are as follows:Based on SL793-2020 Technical Guidelines for River and Lake Health Assessment,and combined with the actual situation of Juyan lake,a health evaluation index system of Juyan lake was constructed,which consisted of target layer,criterion layer,sub-criterion layer,index layer and 18 assessment indexes.After consulting relevant domestic and foreign literatures and consulting experts' suggestions,The weight of 17 assessment indexes in the index layer was determined by the analytic hierarchy process,and the health level of Juyan lake was evaluated by the method of weighting step by step.The results showed that since the implementation of ecological water replenishment project in the Hei River from 2002,the ecological pressure of the Juyan lake has been obviously relieved,and the health level of the Juyan lake has been significantly improved.According to the analysis of data,the scores of hydrological integrity,chemical integrity,morphological and structural integrity,biological integrity,and sustainability of social service in the five sub-criterion layers of Juyan lake were 42.00,57.82,38.44,68.41 and65.56 respectively,which are at sub-healthy,sub-healthy,unhealthy,healthy and healthy levels respectively.The final River and Lake Health Evaluation Score(RHS)of Juyan lake was 58.18,which was at the sub-healthy level.Considering the actual situation of Juyan lake,the weights of target layer and sub-criterion layer were revised by AHP.The revised weights of "ecology" and "function" were 0.89 and 0.11 respectively,and the four sub-criterion layers in "ecology" were 0.15,0.25,0.36 and 0.24 respectively.Considering that Juyan lake has two different periods of non-ice-bound period and ice-bound period,the weights of the indices of "chemical integrity" and "biological integrity" affected are determined by using analytic hierarchy process(AHP).Finally,the weights of two sets of index layers in non-ice-bound period and ice-bound period are obtained.Finally,the health scores of the Juyan lake ecosystem in non-icebound period and icebound period were 51.44 and 50.95,respectively,indicating that the Juyan lake ecosystem was in sub-health state.The main reasons leading to the sub-health status of the ecosystem are as follows :(1)the variation degree of the inflow flow is very large in the hydrological integrity,and the runoff completely depends on the upstream ecological water supply;(2)In terms of chemical integrity,the water quality and nutritional status were poor.The concentration of some pollutants in water far exceeds the class ? water limit value,and the water was between mild and moderate eutrophication.(3)In the morphological and structural integrity,the lake connectivity is poor,the lake area is seriously shrinking,and the vegetation coverage of the bank slope is sparse.The sparse vegetation coverage of the bank slope leads to the poor stability of the lakeshore zone,and the phenomenon of human excavation of canals and human disturbance is serious.(4)The loss of zooplankton was serious,the coverage of macroaquatic plants was low,the biointegrity of macrobenthic invertebrates was poor,and the overall species diversity was poor. |
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