Diagnosis Of Urban River Ecological Health In Coastal Cities Under Complex Hydrodynamic Conditions

The ecological health of urban rivers has been a hot topic in the research of ecological civilization construction and water pollution prevention in China in recent years.Coastal urban rivers are disturbed by complex tidal hydrodynamic forces,and their ecological health diagnosis lack clearer theoretical basis and simulation analysis.Based on the assessment of the habitat suitability of indicator organisms,this paper analyzes the response relationship of the complex water environment factors of coastal cities and rivers,and establishes an ArcGIS-based coastal urban river ecological health diagnosis system.The system has been successfully applied in Guangdang River in Yantai City.And it has important theoretical and practical guiding significance for the ecological assessment of coastal urban rivers under complex hydrodynamic disturbances.The main research results are as follows:?1?Developed large-scale habitat survey methods for coastal cities and rivers.This paper considers the characteristics of coastal cities and rivers,screens out habitat impact factors that meet the characteristics of indicator fish life activities,effectively identifies the range of key impact factors of habitat suitability,and providing good data support for subsequent model establishment and application of fuzzy rules.This method has been applied in different seasons in shopping in Guangdang River,collecting actual data and evaluating the water environment.Among the various factors,the water volume of the Guangdang River is very small,so the flow velocity?V?is slow,the water depth?Dep?is shallow,and the waterfront transfer?Tra?is more stable,so the seasonal changes are not obvious;The slope protection vegetation?Veg?is not significantly affected by the season outside of winter.In terms of comprehensive water quality factors,the ecological environment is the best in spring and winter,followed by autumn and summer.Compared with the freshwater area in the middle and upper reaches of the Guangdang River,the tidal reach does not show significant water quality differences,and is mainly affected by the common complex effects of tidal dilution and pollution of the freshwater area.?2?Established the eco-health model of coastal cities based on fish habitat.The article screens out the factors,such as flow velocity?V?,water depth?Dep?,substrate?Sub?,dissolved oxygen?DO?,ammonia nitrogen?NH₃-N?,slope protection vegetation?Veg?,and waterside transfer?Tra?,as indicators for the evaluation of habitat suitability?SI?at different seasons in different life stages of crucian carp and seven-star perch in the Guangdang river,used to characterize the ecological health status of coastal urban rivers..The results showed that the SI range of the crucian in the spawning period,the crucian in the adult period,and the seven-star bass in the adult period in the Guangdang River are0.24⁰.49,0.26⁰.63,and 0.31⁰.69,respectively.In the spring,the low-flow hydrological characteristics and the high dissolved oxygen quality environment of the Guangdang River determine that the SI of crucian carp in spring is at a low level during the spawning period.The crucian in adult period has better habitat in summer and autumn.The habitat of the seven-star bass in the adult period in the river freshwater area?not the actual living area?in spring and autumn is also theoretically friendly,and the higher SI value than crucian in adult stage also proves this point.The water quality factors such as DO and NH₃-N change more frequently and have a greater impact on the fish habitat.The control and improvement of river water quality is currently a more practical way to improve the habitat suitability of target fish.?3?Analyzed the ecological health of coastal cities under complex hydrodynamic conditions.In this part,the tidal zone of Guangdang River is taken as the research object,three consecutive monitoring sections upstream from the estuary are selected for simultaneous observation,and the prototype hydrodynamic water quality changes during the entire tidal cycle are monitored.Based on the above water environment factor parameter analysis,the habitat suitability changes of the target fish species affected by the tide and river flow are simulated to analyze the coastal urban ecological health under complex hydrodynamic conditions.In the tidal zone,obvious changes in flow velocity?V?and water depth?Dep?caused changes in water quality factors.The DO concentration value is closely related to the change of flow velocity?V?and time.Except for winter,the overall concentration of NH₃-N is greatly diluted by seawater.The summer habitat in this area is most suitable for the crucian in the adult period and the seven-star bass in the adult period.The SI value of the crucian in the adult period is theoretically or practically slightly lower than that of the seven-star bass in the adult period.Among the three monitoring points upstream along the estuary in the tidal zone,monitoring point 3 is a more suitable habitat for crucian carp?spawning or adult?than monitoring point 1 and 2.The difference in the values of SI of the seven-star bass in the adult period at the three monitoring points is extremely small,so the living environment for the seven-star bass in the adult period in the entire tidal zone is very stable.