Assessment and Monitoring of Optically Active Water Quality Parameters on Wetland Ecosystems by Semi-Analytical Modelling: A case study on Harike and Keshopur Wetland over Punjab Region, India

Wetland plays a vital role in sustainable ecological development. They hold balanced environment conditions and filter the surface and sub-surface water and moderate the local weather condition. But now-a-days wetlands are shrinking quickly due to climate change & anthropogenic activities and extinction of wetlands agitates the local environmental conditions with contexts to water and soil conditions. The current study is mainly focussed on assessment and monitoring of optically active water quality parameters viz. chlorophyll-a concentration and total suspended matters on wetland ecosystems over Harike and Keshopur wetland (designated as Ramsar site) in Punjab region, India. The sentinel-2 multispectral imager (MSI) product have been analysed in two phases: Pre-monsoon and Post-monsoon during period from 2018 to 2021 to extract spatial and temporal variations of water quality parameters. A normalised difference water index (NDWI) has been utilized to extract the water and non-water pixels and semi-analytical inversion model is used to retrieve the optically water quality parameters. A key input to semi-analytical inversion model is the pure spectral reflectance of bottom seagrass or sand to invert the corresponding for a given pixel. Accuracy of water column parameters retrievals is depends on the pure end-member of bottom which is used in the model during the inversion. For each pixel in an image, an inversion model run backward to find the best combination of input parameters value to give the closest match between the measured reflectance and the model output. The images of derived chlorophyll concentrations and total suspended matter have been found ranging from 0 to 36 mg/m³ and 0 to 156 mg/m³. This study revealed that semi-analytical model is very helpful to identify the small scale changes in optically active constituents using multispectral imagery. Water quality parameters monitoring is an important indicator to measure the productivity and eutrophication of the river water system. This research will help in understanding water cycle, water conditions and is paramount to researchers, scientists and policy makers for sustainable management. The current study also concluded that the significant reduction of highly biodiversity wetland area is required to conserve.