Spatiotemporal Modelling Approach for Nutrient Export in Sasthamkotta Freshwater Wetland Watershed

Wetlands provide a variety of habitats for different life forms and are essential to human survival. Sasthamkotta Lake, designated as a freshwater wetland ecosystem and a Ramsar Site of international importance is currently facing challenges of nutrient enrichment from the nearby land use features. This study utilizes the InVEST software’s Nutrient Delivery Ratio module coupled with Remote Sensing and GIS (Geographic Information System) to analyse the spatial distribution and temporal variation in the impact of land use on nutrient delivery in the watershed area of Sasthamkotta lake comprising of three panchayats namely Sasthamkotta, Mynagappally and West Kallada. The result reveals that settlement with vegetation followed by open land with vegetation and dense vegetation were the dominant land use classes as well as the key contributors of Total Phosphorus (TP) and Total Nitrogen (TN) in the watershed area. The value of TP exported (varies from 0 to 0.700 million tonnes/km) and that of TN (varies from 0 to 0.450 million tonnes/km) demonstrates that TP export was higher. This could be due to runoff from agricultural land and rubber plantations, discharge from nearby residences, water treatment plant and anthropogenic activities, particularly in the 100 m buffer zone of the periphery of the lake. It also highlights the internal water flow pattern within the lake, which indicates a groundwater recharge zone near the bund region underlining the significance of sustainable land-use planning and management strategies in the watershed.