Ecological Health Evaluation Of The Oiantang River Tidal Estuary Based On Multi-source Remote Sensing Data

Qiantang River is the source of drinking water for Hangzhou and its adjacent areas.A comprehensive test and evaluation for the health condition of Qiantang estuary is an important task for the management of Qiantang River.This article is guided by the river and estuary ecosystem health theory and based on the ecological concept model of PSR(Pressure-State-Response).We take the influence of the pollution from land and the outside of the estuary on the tidal estuary into full consideration.A modified evaluation mode for tidal estuary ecological health with multiple levels and indexes is established based on the existing modes.The model is then applied to the evaluation of Qiantang tidal estuary.The main contents and conclusions are as follows:(1)Guided by the evaluation theories for river and estuary ecosystem health and based on the PSR model,a multi-level evaluation system which is suitable for tidal estuary is established taking full advantage of the remote sensing images with high spatial(Landsat and GF-1)and temporal resolution(COMS/GOCI):1)Multilevel health evaluation indexes:degree of land use change(the index of pressure inputting from the land);the high-frequency dynamic data of suspended sediment,chlorophyll-a,CDOM and DOC from GOCI remote sensing data(the index of pressure inputting from the sea);the indexes of the aquatic environment status:suspended sediment,chlorophyll a,CDOM,DOC,TPP,DIN,DIP,SDD and DO;the indexes of the ecological response of aquatic ecosystems:primary productivity of aquatic ecosystem;2)Evaluation criteria:domestic and foreign relevant evaluation criteria of indicators.3)Evaluation method:objective entropy evaluation method.(2)The modified ecological health evaluation model using remote sensing data is applied to the ecological health assessment of Qiantang estuary.Conclusions are summarized as follows:1)Terrestrial input pressure indicator show that the degree of land use change of the Qiantang River watershed is higher(the comprehensive index above 240)since 23 years,which indicates that the Qiantang River tidal estuary is under high intensity inputting pressure.The concentration of the pressure inputting from the sea show that the characteristics is lower in the north and higher in the south.And it has higher values in the frontier area of Andong tidal flats.Generally,the pressure state of the Qiantang River tidal estuary is in the II level.2)The status of the aquatic environment indexes:the pathological indicators are:suspended sediment,DOC,TPP and DIP;the unhealthy indicators are:chlorophyll a,DIN and SDD;CDOM and DO are respectively in the health and sub-health state.3)The status of the ecological response index:primary productivity is in a state of health.Under the pressure from the deterioration of land usage and the continuing periodical pressure from the tidal sea water which is highly polluted,the natural properties of Qiantang estuary ecosystem have been changed utterly.The ecological pressure from human activities and environmental pollution has already surpassed the ecological capacity of self-maintenance and self-renewal.The work provides theoretical and technical support for the ecological protection and management of Qiantang River and offers new ideas and technical means to the "A total of five water treatment" project of Zhejiang province.