Spatiotemporal assessment of surface water dynamics and quality in Harike Wetland, Punjab, using multi-sensor remote...

Wetlands are critical ecosystems that regulate hydrology, sustain biodiversity, and support human livelihoods, yet they are increasingly degraded by anthropogenic pressures and climate variability. Harike Wetland, the largest freshwater Ramsar site in northern India, is experiencing severe ecological stress due to altered hydrology, agricultural runoff, industrial effluents, sedimentation, and invasive species. This study integrates long-term satellite observations with field investigations to assess spatiotemporal surface water dynamics and water quality variations in Harike Wetland. Multi-decadal Landsat imagery (1984-2024) was used to evaluate long-term changes in surface water extent using the Google Earth Engine (GEE) platform, while Sentinel-2 MSI data (2016-2024) were employed to derive seasonal surface water distribution and optically active water quality parameters, including chlorophyll-a (Chl-a) and total suspended matter (TSM). Seasonal water extent was delineated using the Modified Normalized Difference Water Index (MNDWI), which performed effectively under turbid and vegetated conditions. Results indicate pronounced spatial heterogeneity and long-term shrinkage of peripheral wetland areas, with surface water extent increasing by 8.8% during pre-monsoon (2017-2024) and 3.7% during post-monsoon (2016-2023) periods, largely controlled by monsoonal inflows and regulated discharges. Water quality analysis revealed elevated pre-monsoon Chl-a concentrations (up to 39.6 mg/m³) and TSM levels (up to 153.3 g/m³), reflecting stagnant conditions, nutrient enrichment, and sediment accumulation. Post-monsoon periods showed comparatively lower Chl-a and TSM but higher turbidity due to runoff-driven sediment inflows and dilution effects. Field-based physicochemical measurements validated the satellite-derived results, highlighting the sensitivity of Harike Wetland to hydrological variability and anthropogenic stress. The study underscores the effectiveness of integrated remote sensing approaches for long-term wetland monitoring and recommends strengthened inflow regulation, sediment management, ecological restoration, and continuous satellite-based assessment for sustainable conservation of the wetland.