page_title: Phumdi
section_title: Environmental issues
hierarchical_section_title: Phumdi / Environmental issues
caption_attribution_description: Common water hyacinth (Eichhornia crassipes)
context_page_description: Phumdis are a series of floating islands, exclusive to the Loktak Lake in Manipur state, in northeastern India. They cover a substantial part of the lake area and are heterogeneous masses of vegetation, soil and organic matter, in different stages of decay. The largest single mass of phumdi is in the southeastern part of the lake, covering an area of 40 km². This mass constitutes the world’s largest floating park, named Keibul Lamjao National Park. The park was formed to preserve the endangered Eld's deer subspecies, called sangai in the Meitei language, indigenous to this area.
  Phumdis are used by the local people for constructing their huts for fishing and other livelihood uses, and are inhabited by about 4000 people. Athapums are artificial circular phumdis, built by the villagers as enclosures for fish farming; aquaculture has caused proliferation of the phumdis in the lake.
context_section_description: 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.
  It is also reported that the soil of the park formed by the phumdis is highly acidic, with unsuitable pH conditions for many species of plants to grow and flourish. Further, the acidity of the soil has also adversely affected the fish breeding farms. Recent reports indicate that locals are slicing the phumdis into sizeable pieces and towing them with canoes to sell to fish culture owners.
  A scientific study of the water quality parameters of physico-chemical and microbiological characteristics and role of phumdis in the Loktak Lake has been conducted by collecting surface water samples on monthly basis from 15 stations, representing 5 zones; northern, western, eastern, middle and southern. The test results indicated that water quality in the phumdi area was poor in the northern and southern zones of the lake; test results indicated low dissolved oxygen, low pH (normal range for Loktak Lake is 6.3 to 8.2) high CO₂ and high Biochemical Oxygen Demand (BOD) but the water quality was good in the open water area. Assessment of the total nitrogen content of the macrophyte species of phumdis indicated that the following were present in descending order: Salvinia natans (1.8%), Zizania latifolia (1.6%), Capillipedium sp. (1.3%), Brachiaria mutica (1.2%), Cyperus brevifolius (1.2%), Echinochloa stagnina (1.0%), Phragmites karka (1.0%) and Hedychium coranarium (0.94%). The test results confirmed the fact that the phumdis were efficient in absorbing nutrients from the lake water. However, they deteriorated water quality due to reduced light penetration and accumulation of organic matter in the lake ecosystem.
caption: Infestation of Loktak Lake by water hyacinth
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