Annaiwilundawa Tanks Sanctuary. 03/08/01; Northwestern Province; 1,397ha; 07°42'N 079°49'E. Sanctuary. An ancient system of human-made cascading tanks or reservoirs, ranging between 12 and 50 hectares each and totaling some 200 ha, dating back to the 12th century, which help to sustain traditional paddy fields in the area as well as islets of natural vegetation. In addition to being unique to the biogeographical region, the site harbors quite a few species of threatened fish, amphibians, birds, mammals, and especially reptiles and supports up to 40% of the vertebrate species found in Sri Lanka. The system serves as an important refuge for migratory birds and also supports about 50% of the country's freshwater fish species, including at least three endemic species. Only 3-4 meters deep, it is a highly productive wetland with an array of zooplankton and phytoplankton, which also makes it extremely important for migratory fish. The tanks store water, in this dry region, for irrigation purposes, and also play a major role in flood control, aquifer recharge, retention of pollutants and sediments, and nutrient export. Local communities have practiced sustainable traditional farming and fishing since ancient times, but extension of prawn (shrimp) farms in surrounding areas has resulted in mangrove destruction and pollution and eutrophication caused by waste water releases; other potential threats derive from the spread of two species of alien invasive fish and four of plants and from the use of chemical fertilizers and pesticides in nearby coconut plantations. An upgrade to the status of Nature Reserve, with permanent staff, is foreseen. Ramsar site no. 1078.Most recent RIS information: 2001.