Loktak is the largest fresh water lake in Northeast India and is famous for phumdis (heterogeneous mass of vegetation, soil and organic matter at various stages of decomposition) floating over it.The lake is located at Moirang(Bishnupur District) around 40km from the capital city,Imphal of Manipur. Theetymology of Loktak is Lok= stream and tak=the end. The largest of all the phumdis covers an area of 40 sq. km and is situated on the southern shore of the lake. Located on this phumdi, KeibulLamjao National park is the only floating national park in the world. The park is the last natural refuge of the endangered Sangai( State animal) the brow-antlered deer( Cervuseldieldi).This ancient lake play an important role to maintain the mild climatic condition and hydrological cycle as well as economy of Manipur. It also serves a source of water for hydropower generation, irrigation and drinking water supply. The lake is also a source of livelihood for the rural fisherman who live in the surrounding areas and on phumdis, also known as phumsangs. Human activities has led to serve pressure on the lake ecosystem. 55 rural and urban hamlets around the lake have a population of about 100,000 people. Considering the ecological status and biodiversity values, the lake was initially designated as wetland of International importance under Ramsar Convention on 23rd March 1990. It was also listed under the Montreux Record on 16th June 1993, a record of Ramsar where changes in ecological character have occurred, are occurring or likely to occur.
At the Ithai barrage outlet of the lake, the direct catchment area draining into to the lake is 980 sq.km out of which 430 sq.km is under paddy cultivation, 150 sq.km habitation and 400sq.km under forest cover. The area of the lake is 236.218sq.km comprising large pockets of open water and marshy land formed at the southern part of the Imphal valley up to the confluence of Manipur River and Khuga River. The lake is divided into two zones, namely the “Core Zones”, which is the no development zone or totally protected zone comprising 70.3 sq.km and balance area is called the “Buffer Zone”. Within the lake and on its periphery there are 14 hills of varying size and elevation. In the southern part of the lake are the Sendra,Ithing, Thanga and Karang Islands. Geographically, in terms of biodiversity and human activities pressure, the lake is broadly divided into northern, central and southern zones. The northern zone extends from eastern side of Nambol river near NgaikhongKhunou to Phoubakchao, including MaibamPhumlok, has five main steams/ rivers i.e Manipur, Nambul,Yangoi,Nambol and Thongjaorok rivers flowing into the lake. The zone is separated from the central zone by large Phumdis (varying thickness of 0.4 to 4.5 m) that stretches from northwest to the southeast. During January to March Phumdis in this area are usually burnt for construction of fish cum paddy farms; many large fish farms with raised levees have been built. The central zone extending from AwangLaisoi Pat (western part of Nambol river near NgaikhongKullen) to Laphupat( between Khordak Channel and Imphal river) encloses prominent Islands of Thanga, Karang and Ithing. It has some sub-zones vizLaisoi, Awangsoi, Yennapat, Thorapat etc. It is the main open water zone of the lake which was relatively free from phumdis in the past but over the years athaphums ( artificially created phumdis for fishing) constructed by the villagers for fishing have proliferated choking the entire lake. The state fisheries Department has established a fisheries center within this at Takmu pat for fisheries development. The southern zone encompasses the Keibullamjao National park,Ungamel and Kumbi Pat at the southern part of the lake and the zone is linked with Khuga River by the Ungamel channel. The Imphal River is also linked with this zone by the Khordak channel. The western catchment drained by KangsoibiRiver flows into this zone. Proliferation of phumdis has been observed near the mouth of Ungamel channel, Kumbi Pat, Nongmaikhong and Khordak area. LoktakLake is fed by the Manipur River and several tributaries and UngamelChannel (IthaiBarrage) is the only outlet now. The origin of the Manipur river system and its tributaries which flows in a north-south direction and drains into the lake is from the hill ranges immediately to the west of the lake. Five major rivers with indirect catchment area 7157 sq.km are the Imphal( also called Manipur river),the Iril, the Thoubal, the Sekmai and Khuga. The other major steams which drains into the Lake and which bring in lot of silt are the Thongjaorok, the Nambol, the Nambul, the AwangKhujairok, the AwangKharok, the Ningthoukhong, the Potsangbam, the Oinam , the Keinou and Irulok. The Lake located on the southern side of the Manipur river basin is at the lowest elevation in the valley and other major river flows into the lake except a few rivulets. Several water resources development projects have been developed in the Manipur river basin to meet the growing demands for irrigation and drinking water. The most discussed project is the Loktak Multipurpose project which provides hydropower, irrigation and water supply benefits but has attracted adverse criticism for the drastic alteration caused by the project to the hydrological regime of the LoktakLake and associated wetlands.
A rich biodiversity with habitat heterogeneity has been recorded during a scientific survey carried out between January 2000 and December 2002 in different habitat patches of the Lake. The lake’s rich biological diversity comprises 233 species of aquatic macrophyts of emergent, sub emergent free floating and rooted leaf types. But declining trend of vegetation and important flora are recorded. 57 species of water birds and another 14 species of wetland associated birds have been noted in the lake including 28 spices of migratory water fowl. Also recorded were 425 species of animals-249 vertebrates and 176 invertebrates. The list includes rare animals such as the Indian Python, Sambhar and barking deer. KeibulLamjao national Park is the natural habitat of one of the most endangered deer the brow –antlered deer (Sangai) which was once thought to be extinct. The avifauna recorded in different habitats of the Lake is reported to be declining. In the central part of the Lake water fowl including dabbling duck and diving ducks are reported but their numbers are declining due to proliferation of phumdis. In the habitat part of the rooted plants and others were reported abundant but now show a declining trend. Small hillock( though showing degraded condition) in the lake show big trees and birds of prey such as Milvus migransLineatus and Circus aeruginosus have been recorded on these trees. Fish yield from the Lake is reported to be about 1500 tones every year. Natural capture without the requirement of any lease or license was also in vague in the Lake. The lake fishing is now a mixture of capture and culture system. The old varieties of the local fishes like Ngamu,Ukabi,ngaril, Pangba ,tharak and ngasep stated to be under serious decline and some of them appeared to be extinct in the lake.
The Loktak Lake and its precincts faced serious problem due to loss of vegetal cover in the catchment area and construction of Ithai barrage at the outlet of the lake for multipurpose development of water resources. The degradation of the catchment area has occurred. Deforestation and shifting cultivation in the catchment areas have accelerated the process of soil erosion resulting in the lake’s shrinkage due to siltation. The annual silt flow into the lake is estimated to be 336,350 tons. The nutrients from the catchment area and domestic sewage from Imphal City carried by Nambul River are discharged into the lake affecting its water quality thus encouraging the growth of water hyacinth and phumdis. All these activities have direct bearing on the ecological stability of the lake. Interfere in navigation and overall aesthetic value of the lake are other reported adverse effects.
