基于遥感的官厅水库水质监测研究

Abstract

Because of the advantages of rapidness,wide coverage,low cost,and dynamic monitoring over a long period of time,remote sensing has been widely used for water quality monitoring in recent decades.However,monitoring inland water quality by remote sensing is far behind ocean color remote sensing in both development of remote sensors and monitoring approaches.The development of hyperspectral remote sensing technique has brought much more new possibilities to inland water quality remote sensing.In this study,Guanting Reservoir,which lies between Zhangjiakou(He Bei) and Beijing and once upon a time was one of Beijing' s drinking water sources,is selected to be the research area.In-situ hyper-spectral measurements were conducted by using the ASD Field Spec Pro FR spectroradiometer at 7 different points in Guanting Reservoir in May and at other 18 different points in August.Water samples were also simultaneously collected for laboratory analyses.Sample site position information was recorded via portable GPS and chlorophyll-a concentration of the water samples were measured in laboratory by Lambda950 spectraphotometric.The data indicates that Guanting Reservoir water's chlorophyll-a concentration and tripton concentration was low.With the data obtained in situ and in the laboratory,the biooptical model was built to retrieve the concentrations of tripton,chlorophyll-a and colored dissolve organic matter(CDOM)of summer Guanting water.The retrieve results shows that all-bands matrix inversion method gained the best accuracy,then was five-bands method.Four-bands method got the worst accuracy.Then combining with the aerospace hyper-spectral data CHRIS / Proba,the water quality parameters at the whole reservoir was obtained and spatial analysis was conducted at last.Upstream region of chlorophyll a concentration were less than the downstream region and the Yongding River entrance in the reservoir.Aquatic plants in the upstream area was relatively lush area,because aquatic plants for photosynthesis so greatlyreduce the concentration of carbon dioxide in water was not suitable also need to absorb carbon dioxide for photosynthesis of phytoplankton to survive,so chlorophyll a concentration in the region relatively low.The tripton concentration had similar distribution.The colored dissolve organic matter(CDOM) concentration distribution was different from them.In the upstream areas,due to the decay of aquatic plants,aquatic farming causes rotting animal carcasses,resulting in high concentrations of CDOM in the region,while other waters is relatively low.Distribution could reflect the reasonable Guanting Reservoir chlorophyll-a concentration,tripton concentration and CDOM concentration distribution,the study also shows that the bio-optical model is applicable to Guanting Reservoir water quality monitoring.The method proposed in this work had potential applications in environmental management for improved chlorophyll-a concentration monitoring efficiency in large-scale water bodies.It was also applicable in policy / decision makings needed for early warning and prevention of water eutrophication and the management of water contamination.However,due to the lack of effective and stable satellite data,it is difficult to achieve simultaneous observation satellites and ground,and because the water information is weak,affected by environmental factors and the atmosphere is large,so the water quality parameter remote sensing accuracy assessment is always difficult.