Strong link between land use and water pollution in Manipur’s Loktak Lake catchment: Nagaland varsity study

Kohima, Oct 27 (IANS) A Nagaland University study has sounded an environmental alert for Manipur’s Loktak Lake, one of India’s most iconic freshwater ecosystems and a designated ‘Ramsar Site’.

An official of the central varsity said that the researchers found that changes in land use, particularly agriculture, settlements, and shifting cultivation, are directly deteriorating the water quality of rivers feeding into the lake, threatening its biodiversity and the livelihoods of local communities.

Located in Manipur’s Bishnupur district, Loktak Lake is home to 132 plant species and 428 animal species, and supports hydropower, fisheries, transport, and tourism. It was designated a Ramsar site, or a wetland designated to be of international importance under the Ramsar Convention on Wetlands, signed in Iran’s Ramsar in 1971. These sites are recognised for their ecological significance, such as supporting biodiversity or providing critical habitat for waterfowl.

However, in recent decades, the lake has been listed under the Montreux Record, a global warning list for wetlands undergoing serious ecological damage.

Reduced fish populations, rising pollution levels and increased sedimentation have now become growing concerns.

The study was undertaken by Dr Eliza Khwairakpam of Nagaland University, and the findings were published in international journals.

To understand the root cause, Nagaland University researchers conducted field sampling across nine major rivers — Khuga, Western, Nambul, Imphal, Kongba, Iril, Thoubal, Heirok and Sekmai — that drain into Loktak Lake.

Using detailed Land Use Land Cover (LULC) maps, Dr Khwairakpam compared different types of land activities such as agricultural areas, dense and degraded forests, settlements, ‘Jhum’ cultivation (slash and burn method of farming) and water bodies, against water quality indicators like dissolved oxygen (DO), biological oxygen demand (BOD) and temperature.

Elaborating on the key findings, Dr Khwairakpam, Assistant Professor, Department of Environmental Science of the University, said: “Our study confirms that land use decisions across villages and forest landscapes upstream are directly impacting water quality downstream. This makes community-based land management and stricter control of agricultural runoff and waste discharge crucial for restoring Loktak Lake.”

Further, she added that land management is not just an environmental concern but a livelihood protection strategy for the people of Manipur. Catchment-wide land regulation, sustainable agriculture practices and controlled Jhum cycles will be vital for protecting India’s only floating national park and the endangered Sangai deer habitat within the lake, she stated.

As per the study, the Nambul River was identified as the most polluted, with low oxygen levels and high organic contamination, directly linked to 47 per cent agricultural land and 11 per cent settlement areas in its sub-catchment. The Khuga River showed the second poorest water quality, despite having higher forest cover. Researchers attribute this to extensive Jhum (shifting) cultivation, which was recorded at 42 per cent in the region.

In contrast, rivers such as Iril and Thoubal, which flowed through greater forest-dominated landscapes, displayed better water quality, highlighting the protective role of natural vegetation, it said.

The research was supported by the Manipur government’s Forest Department, which provided LULC maps, and the Manipur Pollution Control Board for field assistance. The study was jointly supported by Nagaland University and IIT Delhi.

Highlighting the need for such studies, Nagaland University Vice President, Prof Jagadish K Patnaik, said: “Nagaland University takes great pride in the significant research contribution made by our faculty and scholars, revealing the strong link between land use and water pollution in the Loktak Lake catchment area of Manipur.”

He said that this study highlights the pressing environmental challenges arising from agricultural runoff, human settlements, and shifting cultivation, which are directly impacting the river water quality in the region.

Nagaland University remains committed to promoting research-driven environmental stewardship that informs policy, fosters sustainable livelihoods, and safeguards our natural ecosystems, Prof Patnaik said.

–IANS

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