Fresh water lakes provide the nutritional requirement for worlds poorest people. kolleru lake is the largest fresh water lake in India existing between west godavari and krishna districts of andhra pradesh.the catchment area of this lake is 6121 square km. this lake discharges excess water in to bay of bengal through a channel called upputeru. which is 65 km long. kolleru wetland receives huge quantity of nutrient rich sediments from flood plains of the rivers. 193 varieties of birds and flora and fauna are found in here. 20,00,000 migratory birds from north america migrates here. but now a days this beautiful lake is getting polluted because of anthropogenic global warming.