Guwahati, June 9: A team of researchers from Nagaland University has conducted an in-depth, year-round study of the Dhansiri River, revealing critical levels of pollution and calling for immediate policy interventions to restore the waterway.
The Dhansiri River, which originates from the Laisang peak in Nagaland and flows 352 kilometres through Dimapur, Chümoukedima, and Assam’s Golaghat district before joining the Brahmaputra, is facing escalating environmental stress.
Covering a catchment area of 1,220 square kilometres, the river supports both ecological systems and human settlements but is under increasing threat from urban runoff, agricultural waste, domestic sewage, and religious activities.
Led by Dr. M. Romeo Singh, Associate Professor in the Department of Botany at Nagaland University, the study analyzed water samples from upstream, middle, and downstream locations across all four seasons.
Researchers used the Weighted Arithmetic Index method to assess 16 physicochemical parameters, allowing them to compute seasonal Water Quality Index (WQI) scores and evaluate potability.
The study found that several key water quality indicators, including turbidity, total dissolved solids, biochemical oxygen demand, and total alkalinity, frequently exceeded national and World Health Organization limits—particularly during the summer.
Water quality was poorest in downstream locations, with samples categorized as non-potable and unfit for human consumption. The researchers observed that pollution levels varied seasonally, with quality declining sharply in summer due to increased runoff and elevated temperatures, and improving slightly in winter.
According to the study, the river’s deterioration is driven largely by unmanaged waste disposal, inadequate drainage systems, and encroachments, which result in the accumulation of pollutants along its course. The researchers highlighted a clear gradient of pollution, intensifying from upstream to downstream, linked to human activities along the riverbanks.
To address the crisis, the team has proposed a series of policy measures. These include relocating dumping sites away from the river, banning direct trash discharge, implementing advanced wastewater treatment technologies, and strengthening local drainage infrastructure. The study also emphasises the importance of regular water quality monitoring and public education campaigns to promote community involvement in river conservation.
“This study serves as an essential basis for the sustainable restoration of the Dhansiri River and other neglected water bodies in India,” said Dr. Singh. “If implemented, the recommended actions could form a national model that combines scientific research, community participation, and policy reform.”
Dr. Singh also noted the broader implications for environmental health and public welfare. Cleaner water would reduce disease risks, support safer agricultural practices, and help restore biodiversity in the region. He added that future research would focus on biological indicators and the presence of heavy metals and emerging pollutants.
Some of the findings were previously published in the International Journal of Environmental Science and Technology in 2022 (DOI: https://doi.org/10.1007/s13762-021-03897-9), contributing to the growing body of work on freshwater degradation in India’s northeastern states.
The Dhansiri River study represents a significant step toward understanding and mitigating the environmental decline of one of the region’s most important yet overlooked rivers.
