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Nature Article & Trip Report => Nature/Travel Destination => Topic started by: priya on January 14, 2011, 05:23:30 pm



Title: Kala wewa
Post by: priya on January 14, 2011, 05:23:30 pm
Kala Wewa is an ancient reservoir in Anuradhapura. This reservoir has a circumference of
40 miles (64.4 km) and has a total area of seven square miles (18.1 km).

Kala Wewa is a large, ancient irrigation tank, which was built by King Dhathusena (455-473
AD) by damming the Kala Oya. This ancient tank was restored in 1887 and again in 1939.
Kala Wewa plays a pivotal role in the modern Mahaweli irrigation scheme, as is one of the
main storage tanks in North-central Sri Lanka. There is a thriving inland fishery in the Kala
Wewa - Balalu Wewa system.

The vegetation, particularly the grass in the drawdown area, provides the primary source of
fodder for sizable herds of cattle and buffaloes in these areas. Kala Wewa is the largest
water storage tank in the Kala Oya basin, with an active surface storage capacity of 123
mcm.

The command area of Kala Wewa is 23,800 ha. Since the implementation of the Mahaweli
Development Project, the tank receives water through the Dambulu Oya, a main headwater
tributary of Kala Oya.

Kala Wewa is located in the dry zone, the area receives rainfall mainly during September -
November (northeast monsoon), with an average annual rainfall of 1,219 mm. The mean
monthly temperature is around 27.9 C while the mean monthly relative humidity varies
from 60% (March) to 80% (December).

During the southwest monsoon period strong, dry winds blow constantly over the plain,
making the area drier. The soil in this area consists of reddish-brown earth and low humic
gley soils typical of the northern lowland region, with some alluvial soil being found in the
river valleys.

The aquatic vegetation comprises mainly of phytoplanktons, while rooted, floating and
submerged macrophytes are also present. Terminalia arjuna and Nauclea orientalis
dominate the seasonally inundated plant communities associated with the tank fringes of
the Kala Wewa.

The undergrowth in this area is not dense and it is ideal habitat for wildlife. Flagship species
such as Asian elephants are frequently recorded in this area. Herbaceous flora mainly
comprises, annuals with a decrease in diversity towards the waterline. The grass Cynodon
dactylon is the only species found in the shallow areas along the waterline. The surrounding
landscape includes natural vegetation types such as dry mixed evergreen forests and manmade
habitats such as chena cultivations, paddy fields and home gardens.

The freshwater fish are dominated by exotic species such as Oreochromis mossambicus,
Labeo rohita, and other carp species. Indigenous species such as Etroplus spp, Puntius spp
and Channa spp. have been recorded from Kala Wewa. Aquatic reptiles include Crocodylus
palustris, Lissemys punctata and Melanochelys trijuga. This is also an ideal habitat for large
colonies of water birds including Pelecanus Philippensis, Phalacrocorax Niger and
Anastomus Oscitans, Phalacrocorax Fuscicollis. Raptors such as Haliaeetus leucogaster and
Ichthyophaga ichthyaetus are also notable species that are found at Kala Wewa.

Mammals that visit the tank include Elephas maximus, Prionailurus viverrinus and Lutra
lutra. Wetland values include hydrological and biophysical values also make Kala Wewa
valuable. Kala Wewa acts as an important water storage tank in the Kala Oya basin. It
stores Mahaweli irrigation water from upstream and releases the water for agriculture in the
Maha season according to downstream irrigation requirements.
 The water level of the
perennial tank fluctuates, depending on the amount of water released for irrigation hence
the tank has an extensive drawdown area, which gets exposed during periods of low water
level.

The biodiversity is such that dry mixed evergreen forest patches are found distributed
around the tank, which harbour valuable timber species such as Manilkara hexandra and
Vitex pinnata. The seasonally inundated swamps are dominated by Terminalia arjuna.
However, residents around the area indulge in fishing activities using bottom set nets, cast
nets and drift nets.

The surrounding forest is a source of medicinal plants while paddy cultivations and chena
cultivations are also found. Animal rearing is a common livelihood particularly in the middle
basin. Locally found reeds are utilised for the production of handicrafts. Brick making also
takes place to some extent using the sediment from the draw down area. There is a threat
that allocation of more land to agriculture and increased conversion of land for the
Mahaweli Irrigation Scheme are potential methods of land use change.

Invasive alien species Lantana camara is extensively found in this area. Other disturbances
include the deforestation of the seasonally inundated forest and clearing of land for
expanding cultivations. As the tank is situated within the culturally important and
touristically popular Anuradhapura District, a large number of tourists visit the area
annually.

Elephant and bird watching are popular activities among the tourists. There is a new hotel
under construction in the area. Conservation measures taken to protect is that part of the
tank catchment and fringing region falls under the Kahalle-Pallekelle Sanctuary

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