Evaluating Wetland Water Quality and Aquatic Plant Dynamics in the Dhemaji and Jorhat Regions of Assam

Abstract

The wetlands of the Brahmaputra floodplain in Assam represent critical freshwater ecosystems that support diverse aquatic biodiversity and provide essential ecosystem services to local communities. This study evaluates the water quality parameters and aquatic macrophyte diversity in selected wetlands of Dhemaji and Jorhat districts of Assam, India. Using standard analytical methods (APHA, 2012), physico-chemical parameters including pH (6.8-7.9), dissolved oxygen (4.5-9.4 mg/L), biochemical oxygen demand (1.8-4.2 mg/L), transparency (35-210 cm), and nutrient concentrations were analyzed across three seasons during 2019-2021. Macrophyte surveys documented 68 aquatic plant species belonging to 28 families, with Cyperaceae, Poaceae, and Nymphaeaceae being the dominant families. The Water Quality Index (WQI) values ranged from 68.6 to 74.8, indicating poor water quality status across all studied wetlands. Significant correlations were observed between dissolved oxygen and species richness (r = 0.76, p < 0.01) and between transparency and macrophyte diversity (r = 0.78, p < 0.01). The invasive species Eichhornia crassipes showed alarming proliferation with relative frequency ranging from 28.4% to 38.2%. The findings highlight the urgent need for conservation interventions and sustainable management strategies to preserve these ecologically significant wetland ecosystems.