Loktak Lake

Topic: Drainage System of India: Rivers, Basins and Patterns · NCERT: Beyond NCERT

Meaning

Loktak Lake is the largest freshwater lake in North-East India. It lies in the Manipur valley, south of Imphal, and is known for its phumdis, which are floating mats of weeds, soil and rotting plant matter [4]. It matters for two reasons. It holds Keibul Lamjao, the world's only floating national park and the last natural home of the sangai deer [4]. It is also a Ramsar site on the Montreux Record, which shows how a dam can harm a wetland [3].

Explanation

What Loktak is and its basic facts

• Lake: a large body of still water sitting in a hollow on the land. A river may feed it, drain it or flow through it.
• Location: in the Manipur valley, south of Imphal.
• Status: the largest freshwater lake in North-East India.
• Ramsar site: a wetland listed under the Ramsar Convention on Wetlands (1971, Ramsar, Iran) as a "Wetland of International Importance".
• Loktak was designated on 23 March 1990 and covers 26,600 ha [1].
• Wular and Sambhar were designated on the same day [1].

Phumdis and Keibul Lamjao National Park

• Phumdis: thick, floating mats of weeds, soil and rotting plant matter that drift on the lake [4].
• Keibul Lamjao National Park:
• It lies on the phumdis in the south of the lake.
• It is the world's only floating national park.
• It was declared a national park in 1977 [4].

• It is the last natural home of the sangai (Manipur brow-antlered deer) [4].

• Why the phumdis matter: the sangai lives on these floating mats, so its home is only as healthy as the phumdis are.

Ithai barrage: how a dam changed the lake

• The barrage:
• It was built on the Ungamel channel, which is the lake's only outlet.

• Its purpose is hydroelectric power and irrigation [4][3].

• Cause → process → result:

• Cause: the barrage keeps the water at a steady high level all year.
• Process: the lake no longer rises and falls with the seasons as it naturally did.
• Result: the phumdis became thinner, the sangai's floating habitat was put at risk, and several native fish species disappeared from the lake [3].

Montreux Record listing

• Montreux Record: the Ramsar list of sites whose ecological character (natural condition) has changed, is changing or may soon change because of human interference [3].
• Loktak was added in June 1993 [3]. The reasons were:
• deforestation in the catchment (the land that drains into the lake)
• water hyacinth, an invasive weed, spreading over the lake

• pollution and the effects of the dam [3]

• Siltation links these threats. Soil washes off bare, deforested slopes and settles in the lake, so the lake gets shallower.

Where it occurs

• Loktak Lake: Manipur valley, south of Imphal, Manipur. Ramsar site since 23 March 1990, 26,600 ha [1].
• Keibul Lamjao National Park: on the phumdis in the southern part of Loktak [4].
• Ithai barrage: on the Ungamel channel, Loktak's only outlet [4][3].
• Other Indian lakes listed on the same day (23 March 1990): Wular (J&K, 18,900 ha) and Sambhar (Rajasthan, 24,000 ha) [1].
• Chilika (Odisha) went onto the Montreux Record in the same year, 1993. It was removed in 2002 after a new mouth was opened in 2000. Loktak is still listed in the study notes.

Don't confuse with

• Wular Lake (J&K): its Ramsar description calls it India's largest freshwater lake [2]. Loktak is the largest freshwater lake in North-East India only.
• Chilika Lake (Odisha): a brackish-water lagoon (partly salty, cut off from the sea by a sandy ridge). Loktak is a freshwater lake. Both were on the Montreux Record from 1993, but only Chilika has been removed (2002).
• Phumdis vs water hyacinth: phumdis are the lake's own floating mats and form the habitat of Keibul Lamjao [4]. Water hyacinth is an invasive weed, and it was one of the reasons Loktak went onto the Montreux Record [3].
• Pulicat Lake: it is not a Ramsar site (as on April 2026) [1]. Loktak is a Ramsar site.

Prelims Hooks

• Keibul Lamjao National Park: on Loktak, Manipur. It is the world's only floating national park, declared in 1977, and the home of the sangai deer [4].
• Loktak, Wular and Sambhar were all made Ramsar sites on the same day, 23 March 1990 [1].
• Loktak Ramsar area: 26,600 ha [1].
• Montreux Record: Loktak was added in June 1993 for catchment deforestation, water hyacinth, pollution and dam effects [3].
• Ithai barrage is on the Ungamel channel, Loktak's only outlet. It is used for hydropower and irrigation [4][3].
• Trap: "India's largest freshwater lake" points to Wular [2]. "Largest freshwater lake of North-East India" is Loktak.

Mains Points

• Dams change lake ecology (GS-III):
• The Ithai barrage keeps Loktak's water level fixed all year, so the natural seasonal rise and fall is lost.
• As a result, the phumdis thinned, the sangai's habitat was put at risk, and native fish were wiped out [3].

• This shows the trade-off between hydropower and irrigation on one side and wetland health on the other.

• How the lake declines (GS-I/GS-III):

• Deforestation in the catchment causes siltation, which makes the lake shallower.
• Water hyacinth and pollution damage it further, and together these put Loktak on the Montreux Record [3].

• When fisheries and the sangai's habitat are lost, both local livelihoods and biodiversity suffer.

• Restoration should fix how water flows:

• Chilika recovered after a new mouth was opened in 2000, letting sea water back in. It was removed from the Montreux Record in 2002.
• For Loktak, the lesson is that a lake development authority and Ramsar listing need to be backed by restoring the lake's natural rise and fall, and by controlling silt and weeds.

Related concepts

• Wular Lake
• Pangong Tso
• Chilika Lake
• Pulicat Lake
• Kolleru Lake
• Vembanad Lake
• Sambhar Lake

Read more

• Lakes of India