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4.2. Study area

Deepor Beel (Fig. 4. 2) lies within the coordinates of 26°06'N to 26°09'N and 91°36'E to 91°41'E and at an elevation of 53m above the mean sea level (Bhattacharyya & Kapil 2010), existing in a former channel that connects the river Brahmaputra with the Sola Beel and the swampy areas of Pandu (MoEF 2008). Located on the mighty Brahmaputra river's southern banks, it is surrounded by National Highway No. 37 on the North, Dakhin Jalukbari, Tetelia and Paschim Boragaon on the East, Rani-Garbhanga Reserve Forest, Chakardew Hill and Chilla Hill on the South-west and Azara and Kahikuchi on the west. There are several educa- tional institutions such as Gauhati University, Assam Engineering College, Assam Science and Technology University, Tata Institute of Social Sciences Guwahati, Government Ayurvedic College and Hospital, Assam Forest School and Girijananda Chowdhury Institute of Manage- ment and Technology on the northern side of the Beel. Although various documents describe Deepor Beel as a 40.14 km2 spread area, it was estimated that the Beel was spread over around a 9.27 km2 area, out of which only 4.1 km2 was covered by water bodies (MoEF 2008).

The depth of the Beel undergoes considerable seasonal variation, 1.5m to 6m, depending on dry or monsoon season (MoEF 2008).

The Deepor Beel receives its water mainly from the Basistha River, which lies on its South- eastern bank. Basistha River, in turn, receives its water from the Bharulu River through the Morabharulu channel. The Bharulu River runs through Guwahati and was once the source of potable water for the city. However, with time, this tributary of Brahmaputra has been turned into a drainage channel, receiving a significant amount of the city's municipal and other wastes along with stormwater runoff (Mozumder et al. 2014). This makes Deepor Beel sus- ceptible to pollution during the monsoon. Moreover, the setup of a municipal solid waste dumpsite at Boragaon near the confluence point of Deepor Beel and the Basistha River (in the wetland's eastern zone) and various small-and-large-scale industries in the wetland's west- ern zone makes it even more susceptible to the deterioration of water quality. In addition, during the lean season, when the water levels are minimum, people from the surrounding villages indulge in excessive unplanned fishing and rice cultivation within the wetland.


| 4Materials and methods e Indian Institute of Technology Guwahati Fig. 4. 2. Study area (Deepor Beel) with LULC map.

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4.2.1. Ecological significance

Deepor Beel serves as a stormwater storage basin, aiding in floodwater regulation for Gu- wahati city during the monsoon season. Surface runoff from the neighbouring hills flows straight into the Beel. Owing to the unique endowment of a vast diversity of flora and fauna, Deepor Beel was declared a wildlife sanctuary in 1989 and included in the Directory of Asian Wetlands (Saikia 2005). Thanks to the congregation of local and migratory birds, the rich avian fauna helped it bag a seat in the list of Important Bird Area (IBA) sites by Birdlife Inter- national (MoEF 2008). In 2002, it was declared a Ramsar site (No. 1207) as a wetland of in- ternational importance for the conservation of global biological diversity and sustaining hu- man life through the ecological and hydrological functions it performs (Bhattacharyya & Kapil 2010). Economically, the Deepor Beel supports about 30% of the 14 surrounding villages through fishing and agriculture (Mozumder et al. 2014). Deepor Beel also plays a vital role in balancing the ecological stability of the area. In 2005, dry fish biomass and fish yield in the lake were reported to be about 1.5 to 3.8 g/m2 and 245 kg/ha, respectively (Saikia 2005).

Saikia (2005) also reported nearly 600 hectares of land in the fringe area of Deepor Beel un- der agricultural practice. Traditionally, Deepor Beel has been used as hunting grounds for various animals, boating, sightseeing, picnic etc.

4.2.2. Land-use-land-cover of Deepor Beel

Fig. 4. 2 shows the LULC mapping of the Deepor Beel’s watershed, delineated through ArcGIS - ArcMap (v. 10.2) and created through ENVI (v. 4.7). It was seen that the entire wetland has been surrounded by heavy built-up on all sides, except the southern part, which is covered by the Rani and Garbhanga forest reserve. On the north-eastern part of the wetland lies the vil- lage of Tetelia, which spreads out up to NH-37 on the east. Tribal villages like Pamohi and Mikirpara lie on the southern fringe of the wetland. The villagers in these places grow boro- paddy planted during the winter season (December to January) and harvested in the pre- monsoon period of April to May. As already mentioned, numerous public institutions are lo- cated on the north and north-eastern side of the wetland. In addition to these, several indus- tries have also come up in the southern and south-western fringes. The presence of industries within the wetland's periphery threaten the ecological structure as the effluent from these industries, partially treated or untreated, ultimately fall into the wetland (MoEF 2008).

The NH-37 surrounds the east and northeast wetland and a PWD road along the Rani- Garbhanga Reserve Forest's northern fringes on the south. The Assam Engineering College Road lies on the north, and the Dharapur-Kahikuchi section of the NH-37 is located on the west. There are also many brick kilns on the northern side of the wetland and a garbage


dumping ground on the eastern side in Boragaon, abutting the wetland margins. According to the reports submitted by the MoEF (2008), the Boragaon Dumpsite presence further exposes the wetland to environmental pollution as there is every possibility of leaching into it during the monsoon season. In fact, as per the C&AG (2012), the location of the Boragaon Dumpsite violates several prescribed parameters stipulated by the Central Public Health and Environ- mental Engineering Organisation (CPHEEO) as given in Table 4. 1. Despite such non-compli- ance, the SWM project, which came into existence in 2006, continues to exist to date.

Table 4. 1. Non-compliance of Boragaon dumpsite (SWM project) with CPHEEO criteria (C&AG 2012).

Criteria of Project

(Location of) As per CPHEEO norms Violation of norms River/Stream The project site should be 100 m away

from any river/stream.

A small stream passes through the site.

Flood Plain No landfill within a 100-year flood plain.

Landfill site is within flood plain.

Wetlands No land fill within wetland. Landfill site is in wetland.

Ground Water table Ground water table to be more than 2 m.

Ground water table is at the ground level.

Airport No land fill within 20 km. Project site is within 10 km of an airport.

Over the years, many railway tracks have come up near the wetland that has dissected it into a number of small pockets. The laying of the railway track and the reclamation of the area outside the track have contributed to the wetland's shrinkage (MoEF 2008).

4.2.3. Biodiversity of Deepor Beel

Deepor Beel is reported as one of the richest wetland ecosystems of Assam. It supports around 232 species of birds, 24 species of mammals, 61 species of fish, 32 species of reptiles and 11 amphibian species (Saikia et al. 2014). The lake's undulating bottom surface provides a unique balance of shallow and deep-water depths across the lake, providing excellent con- ditions for the sustenance of a large variety of plants and animals. Moreover, the presence of Rani-Garbhanga Reserve Hills in the adjoining area provides a suitable habitat for many en- dangered and threatened animals. Deepor Beel's waters support a wide variety of habitats throughout the year due to the water regime's seasonal changes. When the flood level rises in the river Brahmaputra during the monsoon season, water enters the wetland through the Ba- sistha River, raising its water level. During this period, large parts of the wetland are covered by aquatic vegetation like the water hyacinths, aquatic grasses, water lilies and other sub-

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merged, emergent and floating vegetation. The highland areas, which are completely dry dur- ing the winter, are also covered by aquatic and semiaquatic vegetation. As the monsoon re- cedes, the water level in the wetland goes down, exposing significant parts of the submerged land for the habitats of migratory waterfowl, residential waterfowl and terrestrial avifauna.

The wetland also supports a wide variety of lizard species. Various species of flora and fauna within the same ecosystem make the energy transformation system and food web very com- plex (Saikia et al. 2014). Phytoplankton plays a significant role among the lowest levels of the producers in the Deepor Beel ecosystem. The seasonal fluctuations of the water regime also affect the diversity and abundance of the phytoplankton. According to Saikia (2005), there are 18 genera of phytoplankton from the core area of Deepor Beel alone. The available phy- toplankton species were Volvox sp., Anacysistis sp., Oscillotoria sp., Spirogyra sp., Diatom sp., Selenastrum sp., Microcystis sp., Anabaena sp., Zygnema sp., Closterium sp., Hydrodictyon sp., Tribonema sp., Chlorlla sp., Navicula sp., Melosira sp., and Synedra sp. etc. (Sharma 2011). The phytoplankton population blooms majorly during the winter season. The summer season typ- ically records low phytoplankton population density, while pre-monsoon and post-monsoon record relatively higher population density (Chetry 1999). Free-floating, emergent and sub- merged aquatic macrophytes are also abundantly found in Deepor Beel. The free-floating plants such as Eicchornia crassipes, Azolla pinnate, Pistia stratiotes, Lemna minor, Lemna ma- jor, Spirodela polkyrrhiza exist throughout the year and rapidly multiply during the summer season. The emergent vegetation includes Trapa bispinosa, Utricularia flexuosa, Eleocharis pan-taginea, Nelumbo nucifera, N. lotus, Nymphaea alba, N. rubra, Sagitaria sagitifolia, Euryale ferox. Ipomea reptans, Oelia alismoides, Marsilia minuta, Limnophilia aquatic and Monochoria leaqinolis. The submerged plants dominate the Deepor Beel habitat. The foremost are the Po- tamogeton crispum, Valisnaria spiralis, Hydrilla verticillata, Najas foveolata, Paspalum serobic- ulatum. Halophila ovata, H. Beccari and Ruppia maritima. The other cultivated and non-culti- vated plants species available in the wetland are Alium cepa, Pisum sativum, Brassica juncia, B. rugusa, Beta vulgaris, Momordia charantia, Ducus carrota and Triticum aestivum. The weeds found in the wetland, are Eupatorium odoratum, Achyranthus aspera, Cyperus esculonsis, Pharagmites karka, Imperata cylindrica, Vitax trifolia, Accum basilium, Saccharum sponta- neum, Arundo donax, Lentena caemera, etc. (Saikia & Bhattacharjee 1987).