Environment & Ecology24 Concepts & Facts

Phumdis of Loktak Lake & Keibul Lamjao GK Notes

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Phumdis are unique, heterogeneous masses of floating vegetation, decomposing organic matter, and soil that form the defining ecological and limnological feature of Loktak Lake, the largest natural freshwater lake in Northeast India, situated in the Bishnupur district of Manipur. Composed of an interwoven matrix of living aquatic macrophytes, dead plant tissues, peat, and mineral debris bound together in various stages of decomposition, phumdis float semi-buoyantly on the lake’s water column. Their vertical thickness ranges from a few centimeters in young vegetative mats to over two meters in mature, thick formations. A mature phumdi exhibits a remarkable structural buoyancy distribution wherein approximately four-fifths (80%) of its total biomass remains submerged beneath the water, with only the upper 20% protruding above the surface.

Under pristine ecological conditions, phumdis depend upon a dynamic annual hydrological cycle for nutrient replenishment and physical survival. During the dry winter and pre-monsoon months, the natural drop in the water level of Loktak Lake causes the heavier, thicker phumdis to settle onto the lake bed. This contact allows the long, fibrous root systems to penetrate the benthic sediments, extracting essential phosphorus, nitrogen, and minerals while consolidating the organic substrate. When the monsoon floods arrive, the water level surges, causing the buoyant masses to detach from the bottom and resume floating without disintegrating. The largest contiguous and thickest expanse of phumdi, covering roughly 40 square kilometers in the southern quadrant of Loktak Lake, constitutes Keibul Lamjao National Park—the world's only floating national park and the exclusive wild sanctuary for the endangered Sangai deer.

The ecological equilibrium of the phumdi ecosystem was severely destabilized following the commissioning of the Ithai Barrage in 1983 as part of the Loktak Hydroelectric Project. The barrage converted a naturally fluctuating wetland into a permanent, high-water reservoir, eliminating the seasonal grounding and drying phase required by phumdis. Deprived of benthic nutrient contact and subjected to continuous submergence, the phumdi mats have suffered widespread thinning, vertical fragmentation, and structural decay. In recognition of these escalating ecological threats—combined with agricultural siltation and urban sewage inflow—Loktak Lake was designated a Ramsar Wetland of International Importance in March 1990 and subsequently placed on the Montreux Record in June 1993, highlighting an urgent imperative for adaptive water management and wetland restoration.

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Phumdis are heterogeneous floating islands composed of vegetation, dead organic debris, peat, and soil in varying stages of decomposition found in Loktak Lake, Manipur.

Loktak Lake, located in the Bishnupur district of Manipur, is the largest natural freshwater lake in Northeast India.

A mature phumdi exhibits a unique buoyancy profile where approximately 80% (four-fifths) of its thickness is submerged underwater and only 20% is exposed above.

The thickness of phumdis varies from a few centimeters in seasonal pioneering patches to over 2 meters in mature, walking-weight mats.

The southern sector of Loktak Lake contains Keibul Lamjao National Park, spanning approximately 40 square kilometers, which is the world's only floating national park.

Keibul Lamjao National Park is composed entirely of a massive, contiguous, thick phumdi mat that floats on the surface of Loktak Lake.

The floating phumdis of Keibul Lamjao provide the sole natural wild habitat for the endangered Sangai deer (Rucervus eldii eldii), Manipur's state animal.

Naturally, phumdis survive through a seasonal cycle: in dry winter months, lake levels recede, allowing phumdis to ground on the lake bed and absorb soil nutrients.

During the monsoon season, water levels rise, lifting the grounded phumdis to float freely again with renewed structural buoyancy.

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The commissioning of the Ithai Barrage in 1983 for the Loktak Multipurpose Hydroelectric Project permanently elevated the lake water level.

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Permanent high water prevents the natural winter grounding of phumdis, cutting off benthic nutrient absorption and causing the floating mats to thin and fragment.

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The artificial circular phumdis created by local fishermen for fish farming are called "Athaphums" in the local Meitei language.

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Over-proliferation of athaphums causes severe eutrophication, water stagnation, and loss of native submerged macrophytes across Loktak Lake.

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Loktak Lake was officially designated a Wetland of International Importance under the Ramsar Convention in March 1990.

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Due to ecological degradation triggered by the Ithai Barrage, siltation, and pollution, Loktak Lake was added to the Montreux Record in June 1993.

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Loktak Lake is one of only two wetlands in India currently on the Montreux Record (the other being Keoladeo National Park in Rajasthan).

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The Loktak Development Authority (LDA) was established under the Manipur Loktak Lake (Protection) Act, 2006, to oversee wetland conservation and phumdi management.

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Dominant plant species comprising phumdis include Zizania latifolia (wild rice/singkou), Phragmites karka, Saccharum munja, and Eichhornia crassipes (water hyacinth).

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Local fisherfolk belonging to the Meitei community reside directly on large phumdis in floating thatched huts known as "Phumshangs".

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The Manipur government has constructed solar-powered floating schools on phumdis to provide education to children living in floating fishing hamlets.

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Phumdis act as biological bio-filters, absorbing heavy metals, nitrogen, and phosphorus from runoff originating in the Imphal urban watershed.

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Excessive accumulation of rotting phumdi biomass on the lake bed creates thick anaerobic sludge that accelerates lake shallowing and reduces storage volume.

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The Wildlife Institute of India (WII) and MoEFCC run dedicated conservation programs to artificially stabilize phumdis within Keibul Lamjao using eco-friendly bamboo fencing.

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Pumlen Pat, the second largest freshwater lake in Manipur, also historically supported phumdi formations and is proposed as a second home for the Sangai deer.

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Phumdis are unique floating islands of vegetation, soil, and decomposing organic matter found across Loktak Lake in Manipur, the largest freshwater lake in Northeast India. These floating mats behave like icebergs: four-fifths of their thickness stays submerged, while the surface supports plants and fishermen's huts. In the lake's southern sector, these mats form Keibul Lamjao National Park, the world's only floating national park, which serves as the sole wild home for the endangered Sangai deer.

Ecological questions on Loktak Lake feature frequently in UPSC prelims and State PSC exams. A key question pattern focuses on human threats to phumdis. Naturally, phumdis grounded on the lakebed during dry winters to absorb nutrients before floating again in monsoons. The Ithai Barrage, built in 1983, kept water levels artificially high, stopping this seasonal cycle and causing the mats to break apart. Remember that this ecological damage placed Loktak on the Montreux Record.

Phumdis of Loktak Lake & Keibul Lamjao GK Notes

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