Analysis Of Habitat Resilience Potential In Suzhou Ancient City Under Hydraulic Control

The lack of hydrodynamic conditions in the rapidly urbanized plain urban river network leads to poor self-purification ability and serious pollution,which further leads to the loss of river species diversity and hindrance to the restoration of fish and other habitats in urban rivers.Improving controllable hydrodynamic and water quality conditions is one of the effective means for ecological restoration of river networks in plain cities.Therefore,it is of great research significance to establish a model for evaluating the potential of water habitat restoration in plain urban river networks under hydrodynamic regulation.Suzhou,a typical plain river network city in China,was selected as the research object in this study.First,the water environment status of the river network in the ancient city of Suzhou was analyzed by collecting urban river water samples and macrobenthos samples.Secondly,a water habitat restoration potential model of the plain urban river network based on the evaluation of indicator biological habitat suitability was established.Finally,a scenario simulation of the habitat restoration potential of the river network in the ancient city of Suzhou under the control of hydrodynamics was carried out,which using the habitat restoration potential model.The response relationship between the habitat restoration potential of the river network in the plain city and the complex water environment factors was explored.The research results can provide reference value as a theoretical basis for water ecological restoration.The main contents and results of this paper are as follows:（1）The tolerant fish Parabramis pekinensis（juvenile,adult,and spawning stages）and Rhinogobius cliffordpopei was selected as the target fish in the river network in the ancient city of Suzhou,and the hydrological factors of flow velocity（V）and water depth（D）,substrate（Sub）,water quality factors dissolved oxygen（DO）and ammonia nitrogen（NH₃-N）,and river bank slope protection factors in water vegetation（WVeg）and onshore vegetation（LVeg）coverage were chosen as key index factors.The segmented habitat resilience potential model of fish in the river network in the ancient city of Suzhou was established.（2）The Habitat Resilience Potential Index（HPRI）of fish in the river network in the ancient city of Suzhou was simulated,and the results showed that the habitat restoration potential of the tolerant fish bream was higher than that of the sensitive fish,bream,and the adult bream.The restoration potential of fish habitat was higher than the other two periods,followed by spawning period,and the habitat restoration potential of bream at juvenile stage was the worst.The Parabramis pekinensis in the adult stage and spawning stage was not greatly affected by the season,and the B Rhinogobius cliffordpopei had the highest habitat restoration potential in autumn,with an average Habitat Restoration Potential Index（AHPRI）of 0.6,which belonged to the"M"level.The Parabramis pekinensis in the juvenile stage had a high habitat restoration potential in spring due to water quality conditions,with an AHPRI of 0.78,which was at the"H"level.（3）A total of 3049 macrobenthos were collected in the study area,belonging to 3phyla,7 classes,22 families and 50 species.The number of species in spring was more than the other two seasons,and the number of arthropods was the highest,while the average density and average biomass of each site in summer,the largest,658.67 ind/m~2and 171.95 g/m~2,respectively.The species of exogenous river channels were more abundant than those of the river channels in the ancient city and the river channels around the city,and the number of macrobenthos in the upstream area of the river network was more than that in the downstream area.The annual mean values of the three diversity indices Shannon-Wiener diversity index（H’）,Margalef richness index（D）,and evenness index（J）in the whole study area were（1.09±0.15）,（1.40±0.16）and（0.52±0.16）,respectively,which all showing the trend of spring>autumn>summer.Water quality factors dissolved oxygen（DO）,ammonia nitrogen（NH₃-N）and total phosphorus（TP）were the main environmental factors affecting the succession of macrobenthic species communities.The water quality in the study area was evaluated,and the results showed that the river network in the study area was at moderate or even severe pollution level.（4）The habitat restoration potential of target fish before and after water transfer was evaluated,and the response relationship of habitat restoration potential to water quality and hydrodynamic improvement was explore.The results showed that the flow velocity due to hydrodynamic regulation during spawning period greatly increases the habitat restoration potential for the Parabramis pekinensis.There was a significant improvement,and the average habitat restoration potential improvement rate was13.39%;both adult Parabramis pekinensis and Rhinogobius cliffordpopei were slightly improved,with the improvement rates being 1.25%and 1.12%,respectively,while the habitat restoration potential of juvenile bream showed a slight increase.However,the overall habitat restoration potential values were all at a very high level.