Bung (= big pond) Boraped is a half man-made reservoir originating from a natural retarding basin situated close to the city of Nakhon Sawan, where the two rivers, Mae Nam Nan and Mae Nam Ping unite into Mae Nam Chao Phraya (sometimes erroneously called the Menam River). The lake area had been a vast retarding basin known as the Boraped Swamp, which formed a big lake of 600 km² in seasons of high water level while turning into a grass-covered plain with scattered ponds and swampy depressions during the dry season. A dam was built at the head of the main outflowing channel (Klong Boraped) by the Fishery Department of Thailand in 1926-30 mainly for increasing fish production. Part of the swamp thus turned into a lake which has since been known as Bung Boraped. The present lake area is about 106 km² at the spill level, but it varies extensively owing to the water level fluctuation, amounting to as much as 300 km² in time of floods.

The majority of some 30,000 people living around the lake gain their livelihood from both farming and fishing. Since the lake is the largest source of fishery products for central Thailand, the Nakhon Sawan Fishery Station was established at Klong Boraped for the study of fish biology and for stocking the lake with artificially grown fry. Bung Boraped and surrounding swampy areas form one of the non-hunting nature reserves established by the Royal Thai Forest Department. Two development projects have been drafted for tourism development, upgrading aquaculture and utilizing the lake as sources of irrigation and domestic water supply (Q, 1, 2, 3).