Lake Manchar is the largest freshwater lake in Pakistan and one of Asia's largest. It is located west of the Indus River in Sindh. The area of the lake fluctuates with the seasons from as little as 350 km² to as much as 520 km². The lake collects water from numerous small streams in the Kirthar Mountains and empties into the Indus River.
Located west of Sehawan Sharif, Manchar is said to be the largest natural lake in Asia, covering an area of 253 sq. km and maximum 5 meters deep. It is best visited in winter when temperature is comparatively moderate and migratory birds flock to its vast expanse of water and marshlands. The fisher folk living here belong to the aboriginal Mohanna tribe (locally known as Mirbhars meaning Sealords) and are believed to be descendents of the Scythian Meds of Moenjodaro. They live as “boat-people” in their traditional high-powered wooden boats. The lake can be reached by road from Sehwan Sharif. 
Being a natural storage it was free from the defects and drawbacks of an artificial storage. Manchar Lake has been substantially supporting various economic activities. It provided a livelihood for a large number of fishermen, irrigation water for various crops and aquatic plants including lotus. The lake could have also contributed a lot in boosting up tourism industry if its beautification was properly maintained. However due to various reasons the primitive beauty and usefulness of the lake have been degraded.
The human activities have changed significantly the original regime of the lake. Such activities include construction/enlargement of the artificial channels linking the river to the lake and the construction of flood embankments to the north and most important, the Main Nara Valley Drain (MVND), constructed at the time of Sukkur Barrage brings a considerable supply of saline water into the lake. The operation of lake is linked to control the flooding in the barrage-irrigated area and to maintain water levels for irrigated agriculture from the lake itself.
In future, the lake is likely to receive more drainage effluent by construction of drainage network under Right Bank Outfall Drainage (RBOD) schemes. The major potential changes would result from the construction of Sehwan Barrage; under this project the lake would be used as a storage reservoir.
To date, the lake has not been studied in detail. However, few reports have been written on some aspects of the river.
History
The lake was created in the 1930's when the Sukkur Barrage was constructed on the river Indus. The lake is fed by two canals , the Aral Wah Canal and the Danister Canal from the river Indus. Until recently the lake supported thousands of fisherfolk who depended on the freshwater fish they caught in the lake. However, the lake is now undergoing environmental degradation resulting in the water becoming saline killing off the fish and forcing the fisherfolk to look elsewhere for employment.
The degradation has been occurring for a long time but only recently have the effects been felt. The diversion of water from the Indus and a diminished storm runoff from the Kirthar mountains have contributed to the reduction in fresh water supplies. At the same time, saline drainage water from agricultural fields in surrounding areas has started to flow into Lake Manchar.
The lake was a stop-off on the Indus flyway for Siberian migratory birds, but recently the numbers have fallen from 25,000 birds counted in 1988 to just 2800 bird counted in 2002, because the lake no longer provides the birds' main food, the lake fish. In the place of the birds, the lake now hosts a saline water reed.
The lake also provided large volumes of water for irrigation but this has also been reduced and has resulted in a great reduction in the area irrigated by the lake.
