Construction And Application Of River Health Assessment Index System In Guanzhong Region

Along with the rapid economic development and improvement of human activity in strength a series of river ecological health problems such as water pollution,habitat degradation,water resources shortage and biodiversity reduction have attracted much public attention.River health assessment,which relies on appropriate indicator system and assessment methodology making in terms of regional environmental background and protection needs,is the main measure of scientific river health problems diagnose.In this study,the assessment index system of river health in Guanzhong region have been made to evaluate the health of Shichuan River in wet and dry season respectively.Meanwhile,the microbial index of biotic integrity(M-IBI)assessment system was used to evaluate the health of Shichuan River,so as to verify the accuracy of assessment results and the effectiveness of MIBI assessment method.This assessment index system could provide a direction for river health protection and management in Guanzhong region,and the basis for rapid river health monitoring by M-IBI assessment method.The main conclusions of this study are shown as follows:(1)Basing on the relevant researches and norms,an assessment index system for river health in Guanzhong region have been established in this study.The assessment system contained 15 assessment indicators,a total of 5 criterion layers,including water environment,water ecology,water resources,water habitat and water security.(2)By using the assessment index system,the health status of Shichuan River have been assessed in wet and dry season respectively.The results showed that the health status of Shichuan River was same in two seasons,reaching up to sub-health closing to health.Three main tributaries were healthy,and the main stream was in the state of sub-health closing to unhealth.According to the index scoring,the health problems included water environment,water ecology,water resources,water habitat and water security followed.The water environment quality in main stream was poor and the nutrient level in main stream and Qinghe River was high.The biodiversity level of Qinghe River was low,and the biodiversity level of main stream decreased in dry season.Meanwhile,the risk of diatom bloom existed in main stream and Qinghe River in dry season.The utilization rate of water resources in the basin was unduly high.The longitudinal connectivity of main stream,Juhe River and Qinghe River was hindered,and the buffer zone width of main stream and Qishui River was insufficient.It was difficult to guarantee the flood control of the Qishui River and the Juhe River.(3)A total of 69 phyla,183 classes,462 orders,742 families,1461 genera,20090 ASVs have been identified from the sediment of Shichuan River.Results showed that salinity,oxidation-reduction potential,water temperature and chemical oxygen demand were the key environmental factors affecting the distribution of sediment microbial communities.According to the standardized method of IBI assessment system construction,4 core biological parameters were selected to calculate M-IBI scores,and the M-IBI assessment system of Shichuan River was made by using the analogy method.The assessment results showed that the Shichuan River was in the state of sub-health closing to health on the whole in wet season,in which Qishui River and Juhe River were in a very healthy or healthy state,and the main stream and Qinghe River were in a sub-health state.Shichuan River presented a health state in dry season,among which three main tributaries were healthy,and the main stream presented a sub-health state.(4)Comparing the M-IBI assessment with the index system of assessment,the results showed that M-IBI scores in the two seasons were significantly positively correlated with the comprehensive water quality scores.It’s the same with M-IBI assessment system scores and index system scores,indicating that the results obtained by the two assessment methods were consistent on the whole and that the M-IBI assessment method established in this study could effectively reflect the health status of Shichuan River.This study provides a theoretical and practical basis for the health assessment of river and gradually establishing health archives of river in Guanzhong region.Additionally,this research also provides an application for realizing the M-IBI assessment method to monitor river health.