Optimization For Ecological Monitoring Sites And Health Evaluation In The Yellow River Basin(Ningxia Section)

In order to improve the effectiveness and representativeness of water ecology monitoring in the Yellow River Basin(Ningxia section),to explore the health of water ecology and environment in the Yellow River Basin(Ningxia section),and to provide support and basis for the high-quality development of the ecological environment in the Yellow River Basin.According to the principles and laws of monitoring site placement,115 existing monitoring sites were used as the research objects,and also for the convenience of research and later site optimization,the sampling sites were divided into 7 areas based on the geographical distance between sites and the existence of hydraulic connection,which were the northern water system,the central water system,the southern water system,the Diannong River basin,the Zhongwei water system,the Kushui River basin,and the Qingshui River basin.Habitat quality index surveys,water environment sample collection,and aquatic organism sample collection were conducted at 115 sites in April,July,and October 2021,respectively,to score water quality and construct habitat composite index and biological integrity index(IBI).The results of water quality scoring,integrated habitat index and biological integrity index of each regional sampling site were used as indicators,and the optimized sites were analyzed by systematic cluster analysis and physical element analysis,and the optimized sites were determined by combining the results of the two optimization methods and the actual geographic placement of monitoring sites,and the health evaluation was conducted by the integrated biodiversity evaluation method and the integrated biological integrity evaluation method.The main results of the study were as follows.(1)The reference and impaired sites in the study area were determined by water quality scoring and habitat composite index obtained based on habitat quality survey,with ND6 and ND9 for the northern water system;CD 10 for the central water system;SD2 for the southern water system;DN2 and DN4 for the Dennong River basin;ZW9 and ZW20 for the Zhongwei water system;KS12 for the Bitterwater River basin;and QS1 for the Clearwater River basin.(2)After the distribution range analysis,discriminatory ability analysis and correlation analysis,there were 5 indicators for the construction of P-IBI in the northern water system,1 indicator for the construction of Z-IBI,10 indicators for the construction of B-IBI,and 5 indicators for the construction of M-IBI.There were 6 indicators for the construction of P-IBI,7 indicators for the construction of Z-IBI,10 indicators for the construction of B-IBI,and 2 indicators for the construction of M-IBI in the central water system.There were 5 indicators for the construction of P-IBI,9 indicators for the construction of Z-IBI,10 indicators for the construction of B-IBI,and 1 indicator for the construction of M-IBI in the southern water system.There were 3 indicators for the construction of P-IBI;6 indicators for the construction of Z-IBI;5 indicators for the construction of B-IBI;and 2 indicators for the construction of M-IBI in the Diannong River Basin.There were 4 indicators for the construction of P-IBI in the Zhongwei water system;5 indicators for the construction of Z-IBI;6 indicators for the construction of B-IBI;2 indicators for the construction of M-IBI;4 indicators for the construction of P-IBI in the Kushui River basin;8 indicators for the construction of Z-IBI;9 indicators for the construction of B-IBI;and 4 indicators for the construction of M-IBI.There were 4 indicators for the construction of P-IBI;8 indicators for the construction of Z-IBI;5 indicators for the construction of B-IBI;and 4 indicators for the construction of M-IBI in the Qingshui River Basin.(3)The overall optimization result was to optimize the original 115 sampling points to 68 points.The northern water system was optimized from the original 10 points to 7 points;the central water system was optimized from the original 15 points to 8 points;the southern water system was optimized from the original 12 points to 8 points;the Diannong River basin was optimized from the original 27 points to 11 points;the Zhongwei water systen was optimized from the original 23 points to 16 points;the Kushui River basin was optimized from the original 12 points to 9 points;the Qingshui River basin was optimized from the original 16 points to 9 points.(4)The evaluation results of water ecological health in the optimized points were mostly average and subhealthy,with subhealthy predominating.The points with poor biodiversity comprehensive evaluation results were mainly concentrated in the Kushui River Basin,and the sites with healthy evaluation results were mainly concentrated in the Zhongwei water system.The points where the comprehensive evaluation result of biological integrity was healthy were mainly concentrated in the northern and central areas.The main reasons for the differences between the comprehensive evaluation results of biodiversity and the comprehensive evaluation results of biological integrity were the tolerance degree of different orcanisms to the environment,the habitat quality condition,and the water quality condition.