Evaluation Of Ecological Health Of Small River Based On Herbaceous Plants

With the rapid economic development,urbanization and rapid population expansion,the disturbance of human activities to rivers is increasing day by day,and the health problems of rivers are becoming more and more serious.The health status of rivers not only determines the evolution and development of rivers themselves,but also affects the survival and development of human society.Guangdang River,as an urban River in Yantai,also faces the same problems,especially the rapid growth of enterprises and population in the basin has brought strong impact on the water environment of Guangdang River and affected the ecological health of Guangdang River.In this paper,the data of species,distribution area,growth characteristics of typical river herbsand and river artificial structures of herbs in Guangdang River are obtained by field investigation and GOOGLE EARTH remote sensing image software.The plant tolerance was determined by estimating the value of ecological conservation coefficient,and the ecological health evaluation index system with herbaceous plants as indicator species was established.Based on the combined weights of evaluation indexes of analytic hierarchy process and coefficient of variation method,a linear weighted summing evaluation model was constructed,and an evaluation standard based on the ecological health index of reference reach was formulated to evaluate the ecological health of Guangdang River.Obtain the following findings.(1)Through field investigation and GOOGLE EARTH remote sensing image software:First,it was found that there were 63 species of herbaceous plants belonging to 36 families and 59 genera in 10 evaluation stages of Guangdang River.In the reference reach,there are 17 species of herbaceous plants,belonging to 9families and 15 genera.Secondly,the total coverage of plants in evaluated river sections 3~#,4~#and 9~#exceeds more than half of the area of evaluated river sections,while the total coverage of plants in evaluated river sections 1~#,5~#and 10~#are not higher than 10%of that of evaluated river sections.Third,among the 10 evaluation sections of the Guangdang River,the reed growth in the 4~#evaluated river section is the best(all weighing 0.416 kg,with a plant height of 4 m),and the reed growth in the 6~#evaluated river section is the worst(all weighing 0.08 kg,with a plant height of 2 m).The average weight of Phragmites australis in other evaluated river sections is between 0.10 and 0.40 kg,and the plant height is between 1.9 and 3.5 m.Plant tolerance was determined by estimating the ecological conservation coefficient(CC).It is concluded that among the 63 herbs of Guangdang River,except Coix,iris flavescens and Barracuda grass,the others are basically tolerant species.Tolerant species are absolutely dominant in species,quantity and area.(2)Through the investigation of artificial structures in the evaluated river,it is concluded that there are 21 bridges on the Guangdang River,among which 14 are important bridges.There are 23 dams on the Guangdang River.Among them,9 dams have large water level drop.Among the 10 evaluated sections of the Guandang River,3~#is non-hardened,9~#is slightly hardened,2~#,4~#,5~#,6~#,8~#and 10~#are moderately hardened,7~#is severely hardened and 1~#is severely hardened.There are 18 sewage outlets on both sides of the Guangdang River.The field investigation and visit results show that the four sewage outlets that are discharging sewage mainly discharge domestic sewage.(3)The overall ecological health evaluation result of Guangdang River trunk stream is"sub-health".Among the 10 evaluation stream segments of Guangdang River from downstream to upstream,one stream segment with the evaluation result of"health",that is,9~#evaluation stream segment;There are 7 stream segments with sub-health evaluation results,including 2~#,3~#,4~#,5~#,6~#,8~#and 10~#evaluation stream segments;There is one stream segment whose evaluation result is"unhealthy",that is,7~#evaluation stream segment;There is one stream segment whose evaluation result is"bad",that is,1~#evaluation stream segment.According to the evaluation results and combined with the investigation of human activities,the reasons are analyzed,and recovery suggestions and countermeasures are given.The results and conclusions of ecological health assessment of Guangdang River can not only provide scientific basis for the restoration of ecological health of Guangdang River,but also provide reference for the establishment of a constantly improving river ecological health assessment system.