Loktak lake

Loktak lake (Meitei: ꯂꯣꯛꯇꯥꯛ ꯄꯥꯠ; Old Manipuri: ꯂꯣꯛꯇꯥꯛ ꯄꯥꯠ) is the largest fresh water lake in the North East India and the only floating lake on earth. The lake houses the Keibul Lamjao National Park, the only floating national park in the entire world.

The lake is best known for the presence of the circular floating biomasses commonly known as Phumdis in Meitei language (Manipuri language). It is truly a unique feature of this natural water body, not only in India but in the entire world.

Geographically, the lake is the outlet of most brooks, streams, rivers and rivulets originated from the different mounds, hillocks, hills, mountains and peaks of Manipur. The lake serves as the major source of livelihood for the fishermen communities.

It also attracts a lot of tourists both from outside and inside India.

In the last few years, the number of floating home stays and floating restaurants, built over the floating natural biomasses (phumdis) in different parts of the lake, is increasing by leaps and bounds, so as to meet the demands of the increasing volume of tourists in the upcoming years.

The proliferation of phumdis, coupled with severe infestation of the lake by water hyacinth, has substantially impeded water circulation and caused an increase in siltation and deposit of pollutants in the lake ecosystem. The building materials used to build huts on the phumdi blocks sunlight from reaching the lower depths of the lake water, which has resulted in formation of vertical profiles of the lake water body and decomposition. Further, pesticides and insecticides are used for catching fish or as insect repellent. Processes of decay release toxic gases such as methane and hydrogen sulfide, and reduce dissolved oxygen. This causes the lake water to degenerate into a eutrophic condition, creating a dead water zone called the hypolimnion. Above the hypolimnion is a thin layer, known as epilimnion, where fish survive to some degree. The benthal is becoming increasingly thick, causing not only pollution of the lake water, but an increase in the shallow part of the lake.

It has been reported that the construction of Ithai Barrage has altered the Loktak Lake and its ecosystem. Siltation has reduced the water holding capacity and has consequently had a negative impact on the power generation capacity at the Loktak Hydro Electric Power Project. Thinning of the phumdi in the Keibul Lamjao area has affected the habitat of the sangai, and other aquafauna, avifauna and flora are on the decline; the 35 species (5 mammals, 3 birds, 9 reptiles, 3 amphibians, 12 fishes, 2 molluscs and 1 annelid) are reported to be disappearing gradually.