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 Sunday times |