Eutrophication and water quality assessment due to non-point pollution sources using tropic status and remote sensing index of wetlands in Guwahati city,India
Restricted accessResearch articleFirst published online 2026
Eutrophication and water quality assessment due to non-point pollution sources using tropic status and remote sensing index of wetlands in Guwahati city,India
Eutrophication is a nutrient-driven shift in trophic status characterized by the appearance of green or blue green algae and declining water quality. Non-point source (NPS) pollutants are diffuse pollutants originating from multiple sources like agriculture runoff, urban waste, animal or human activities, etc. are major drivers of trophic transitions and algal proliferation. However, their seasonal influences on nutrient balance and trophic state remain understudied. This study provides an integrated framework combining water quality parameters, Carlson trophic state index (CTSI), Redfield ratio, and normalized differentiated chlorophyll index (NDCI) to understand the effect of NPS on nutrient loading and trophic transition across three major wetlands in Guwahati city, Deepor Beel, Dighalipukhuri, and Jorpukhuri during the post-monsoon season. Water quality parameters including temperature, pH, EC, TDS, DO, chlorophyll-a, NO3−, TKN, TN, TP, PO43−, and COD were analyzed from sampling points vulnerable towards NPS pollution across the wetlands. Results showed severe eutrophication intensity with CTSI values ranging from 113 to 115 in Deepor Beel, 110 to 114 in Dighalipukhuri, and 108 to 114 in Jorpukhuri. Redfield ratio of all the three wetlands indicated strong nitrogen dominance (TN/TP >16), with Deepor Beel showing highest spatial heterogeneity, while Dighalipukhuri and Jorpukhuri remain consistently phosphorus-limited across all points. Overall eutrophication intensity is highest in November across sites, with multiple hotspots exceeding TN/TP >50. NDCI mapping validated these findings, showing elevated chl-a concentrations along the pollution-prone margins of Deepor Beel. Across all wetlands, lower DO coincided with elevated chlorophyll-a, phytoplankton driven turbidity (Tchl-a > Tsd) and warmer post-monsoon temperatures are consistent markers of high eutrophication.
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