Dipor Bil, also spelt Deepor Beel (Pron: dɪpɔ:(r) bɪl) (bil or beel means "lake" in the local Assamese language), is located to the south-west of Guwahati city, in Kamrup Metropolitan district of Assam, India. It is a permanent freshwater lake, in a former channel of the Brahmaputra River, to the south of the main river. In 1989 4.1 km² of the area was declared as a wildlife sanctuary by the Government of Assam. It is also called a wetland under the Ramsar Convention which has listed the lake in November 2002, as a Ramsar Site for undertaking conservation measures on the basis of its biological and environmental importance.
Considered one of the largest beels in the Brahmaputra valley of Lower Assam, it is categorised as representative of the wetland type under the Burma monsoon forest biogeographic region.
The Dipor Bil is reported to provide, directly or indirectly, its natural resources for the livelihood of fourteen indigenous villages (1,200 families) located in its precincts. Freshwater fish is a vital protein and source of income for these communities; the health of these people is stated to be directly dependent on the health of this wetland ecosystem. A member of Deepor Beel Fishermen's Cooperative Society has succinctly stated: "Our forefathers protected this wetland and we are committed to do the same as we depend on the wetland for our livelihood. We will protect this wetland at any cost and against any odds".
Access
It is located 13 km South West of Guwahati on the National Highway (NH. 31), on the Jalukbari-Khanapara bypass, alongside its north western boundary. PWD road skirts the northern fringe of the Rani and Garbhanga Reserve Forests on the south. The National Highway 37 borders the beel on the east and north-east and the Assam Engineering College Road on the north. Also, minor roads and tracts exist in the vicinity of the beel. The beel is about 5 km from the Guwahati Airport (LGB Int. Airport). A broad gauge railway line skirts the lake.
Topography and geology
The beel is bounded by the steep highlands on the north and south, and the valley formed has a broad U-shape with the Rani and Garbhanga hills forming the backdrop. The geologic and tectonic history of the region provide the links to the hydrology and channel dynamics of rivers and pattern, and intensity of land use in the area. It is commonly stated that the beel together with those adjoining it are an abandoned channel of the Brahmaputra system.
While the beel and its lowland fringe are said to be underlaid by recent alluvium consisting of clay, silt, sand and pebbles, the highlands immediately to the north and south of the beel are made up of gneisses and schists of the Archaean age.
Hydrology
The Basistha and Kalmani rivers and local monsoon run-off are the main sources of water to the lake, between May and September. Khonajan channel drains the beel into the Brahmaputra river, 5 km to the north. It acts as a natural stormwater reservoir during the monsoon season for the Guwahati city (stated to be the only major storage water basin for the city's drainage, with about four metres depth of water during monsoon dropping to about one metre during the dry season.
The beel has a perennial water spread area of about 10.1 km2, which extends up to 40.1 km2 during floods. However, an area of 414 ha has been declared as "Deepor Beel Sanctuary" by the Government of Assam. As per a Remote Sensing Study the wetland area is reported to have reduced to 14.1% (405 ha) from 1990 to 2002.
Temperatures in the beel vary from 10.60 to 320C. During the winter months, when the size of the lake reduces in area by about fifty percent, the shore area (up to one kilometre) is cultivated with rice paddy when the climate is also relatively cool and dry. The tropical monsoon climate prolongs from May to September when it is humid. Pre-monsoon showers are experienced between March and May.
Flora
The hydrophytic vegetation of the beel has been classified, based on ecological adaptation, into the following categories with their floristic elements. These are: Aquatic vegetation like Giant Water Lily, water hyacinth, aquatic grasses, water lilies and other submerged, emergent and floating vegetation are found during the summer season. In the dry areas, during winter, aquatic and semi-aquatic vegetation are seen In deep open water area, marshy lands, mud flat, emergent vegetation, water hyacinth patches, net-grass land patches are reported Migratory water-fowl, residential water-fowl and terrestrial avifauna are common in paddy field areas, dry grassland areas and scattered forest areas.