Guwahati, Oct 27: A new study by Nagaland University has raised serious environmental concerns over the deteriorating water quality of rivers feeding into Loktak Lake — one of India’s most iconic freshwater ecosystems and a designated Ramsar Site in Manipur. The research confirms that agricultural runoff, human settlements, and shifting cultivation in the Loktak catchment are directly degrading river water quality, with the Nambul and Khuga rivers identified as the most polluted due to high land-use disturbances.
Loktak Lake, home to 132 plant species and 428 animal species, supports hydropower, fisheries, transport, and tourism in Manipur. However, in recent decades, it has been listed under the Montreux Record — a global warning list for wetlands facing serious ecological threats. Declining fish populations, rising pollution levels, and increased sedimentation have made its restoration an urgent environmental priority.
The study, led by Dr. Eliza Khwairakpam, Assistant Professor at Nagaland University’s Department of Environmental Science, was published in the International Journal of Environment and Pollution (https://doi.org/10.1504/IJEP.2025.148717). It examined how different land-use patterns — including agriculture, settlements, forests, and Jhum (shifting) cultivation — are influencing water quality indicators such as dissolved oxygen (DO), biological oxygen demand (BOD), and temperature across nine rivers: Khuga, Western, Nambul, Imphal, Kongba, Iril, Thoubal, Heirok, and Sekmai.
According to the findings, the Nambul River exhibited the highest levels of organic contamination and the lowest oxygen levels, attributed to extensive agricultural activity (47%) and settlements (11%) in its sub-catchment. The Khuga River followed as the second most polluted, with poor water quality linked to extensive Jhum cultivation covering 42% of the region. In contrast, the Iril and Thoubal rivers, which flow through forest-dominated landscapes, recorded better water quality — underscoring the crucial role of natural vegetation in maintaining healthy freshwater systems.
“Our study confirms that land use decisions across villages and forest landscapes upstream are directly impacting water quality downstream,” said Dr. Khwairakpam. “Community-based land management and stricter control of agricultural runoff and waste discharge are crucial for restoring Loktak Lake.”
She further added, “Land management is not just an environmental concern but a livelihood protection strategy for the people of Manipur. Sustainable agriculture, controlled Jhum cycles, and catchment-wide land regulation will be vital to protect India’s only floating national park and the endangered Sangai deer habitat within the lake.”
Prof. Jagadish K Patnaik, Vice Chancellor of Nagaland University, commended the research, saying, “This study highlights the pressing environmental challenges arising from agricultural runoff, human settlements, and shifting cultivation, which are directly impacting river water quality in the region. Nagaland University remains committed to research-driven environmental stewardship that informs policy and safeguards natural ecosystems.”
The study was supported by the Forest Department, Government of Manipur, which provided Land Use Land Cover (LULC) maps, and the Manipur Pollution Control Board, which assisted in fieldwork. The research received joint institutional support from Nagaland University and IIT Delhi.
