Physico-chemical assessment of water quality and primary productivity of the River Kaldiya, Assam (India)

The current study was carried out to assess the primary productivity and water quality of Kaldiya river of Assam. The period of the study was from the month of October to December. Various physico-chemical parameters such as temperature, pH, alkalinity, hardness, dissolved oxygen were analysed during the study. The Weighted Arithmetic Index method (WAWQI) was used to determine the water quality. Our study revealed that temperature of the river water decreased from a range of 21-24°C in October to 16-20°C by December, while pH levels remained alkaline (7.41 to 7.82). Dissolvedd oxygen, alkalinity and hardness were found to be at normal level. The Water Quality Index (WQI) for site-I was observed to be stable (59.94) across all three months; site-III showed lowest WQI value (49.99) in the month of October. However site-II showed highest value of WQI (69.46). The study also quantified the metabolic rates. The recorded Gross Primary Productivity (GPP) values were 103 -117 mgC/m3/hr, 115-125 mgC/m3/hr and 88-93 mgC/m3/hr for site-I, site-II and site-III, respectively across all three months. Correlation analysis confirmed that WAWQI is strongly influenced by biological activity, showing a high positive correlation with Net Community Productivity (NCP) (r=0.765) and GPP (r=0.721).