Flanked on the east by the Indus,  the Laki hills in the south and Khirthar hills to the west, Manchar Lake is a large, shallow freshwater body, formed by natural depression. It is situated at a distance of about 18 km west of Sehwan. The northern and north-eastern boundaries are formed by flood protection dykes, which were constructed in 1932. The lake covers an area of about 246 sq km.

Manchar Lake is a significant water body in Sindh, with a high ecological significance. It meets variable water requirements, ranging from drinking-water and domestic use to agriculture and fisheries. It is also an important wetland site of international significance.

Manchar Lake provides livelihood for fishermen, water for irrigation including cultivation of lotus, tourism promotion, domestic use and acts as breeding ground for migratory birds. Manchar Lake is classified as an unprotected wetland. According to a survey conducted over six decades back, there were about 200 different species of fish in the lake. Current position shows that 14 fish species have died and several others are under severe threat of extinction.

Fishing in Manchar Lake is an important economic activity for the people, living in the adjoining areas. Due to the deteriorating water quality and increased salinity, the fish yield has declined significantly. In 1950, the fish catch was reported to be 3,000 tons/year. This was reduced to 300 tons/year in mid-nineties. Presently, the fish catch is just few tons per year, with the quality of fish being poor and black in color. Most fishermen have migrated elsewhere to meet their economic needs.

Due to lake's water pollution (salinity more than 4,000 ppm - parts per million; presence of toxic metals, agro-chemicals and fertilisers), migratory fauna, including beautiful cranes no longer fly to Manchar Lake. Not only does the lake stand completely abandoned by its flying visitors; the indigenous population of birds has also diminished considerably. Manchar Lake receives freshwater from two sources Indus River and hill torrents from Khirthar hills.

Manchar Lake is linked to Indus River through three canals (Danistar Canal, Aral Manchar Canal, and Aral Laki Canal). Freshwater flows from Indus River to Manchar Lake only when there is sufficient hydraulic gradient.

Runoff from hills occurs only when there are flash floods, caused by heavy rains. On average basis, flash floods occur once every three years. Freshwater flows from hills, therefore, are erratic and unpredictable. Besides, its quantity is relatively low. Because of its unpredictability, this source of water cannot be taken as a dependable source for replenishment purposes.

Manchar Lake is linked with Main Nara Valley Drain (MNVD), which supplies saline water. MNVD is a major natural and artificial drainage canal which receives saline agricultural return flows from irrigated areas located upstream. The storage capacity of the lake has reduced significantly due to sedimentation which is relatively high. This is indicative of the high silt load and other settleable solids in the effluents discharged into the lake.

Water quality of Manchar Lake can be summarised as reduced freshwater inflows, increased saline and wastewater inflow, agricultural return flows (nutrients and insecticides) and reduced storage capacity due to sedimentation. Some problems pertain to the watershed area, while others pertain to the lake itself. Filling of the lake from the river and subsequent release of water would help in controlling lake water salinity. In fact, this is considered as a major, cost-effective step for controlling salinity level in Manchar Lake. Increased freshwater inflow can be achieved by enlarging the channels linking the lake with the river. Pumping stations are another source which could be used to increase freshwater inflow for instance from Rice Canal located at a distance. The inflow to and outflow from the lake needs to be controlled not only in terms of volumetric capacity and quality as well. This is crucial for  lake rehabilitation.

In case of drinking-water, the parameters of concern are fecal coliforms, total coliforms, turbidity, odour, salinity and presence of heavy metals whereas for agricultural use, sodium adsorption ratio and total dissolved solids (electrical conductivity) are an issue. For fisheries, salinity is a concern which in the past varied from 500 to 4,000 ppm.

According to World Health Organisation drinking-water guidelines (2006), the desirable maximum level of salinity in drinking-water is 500 ppm. The absolute maximum acceptable level is 1,500 ppm. For agriculture, the salinity level can be safely extended up to 2,000 ppm. Fisheries requirement varies according to fish but typically, the salinity value for fisheries in freshwater should not exceed 1,000 ppm.

A number of villages located in the vicinity of lake would benefit by the installation of a centralised low-cost water treatment plant. The villagers may not be in a position to share the capital cost but they could contribute in the operation and maintenance of the plant, as clean water for them is a high priority issue.

The federal government has undertaken a project to convey saline effluents to the sea but the project has run into problems and its completion date remains undecided. With saline effluents diverted to large evaporation ponds, freshwater from the river would improve water quality of the lake. For about nine out of 12 months, low water level in the river prevents the flow of water from river to the lake. Installation of pumps would supply water to the lake through round-the-clock pumping.

In the absence of natural infrastructure (e.g., wetlands) and engineered infrastructure (e.g., dykes, wastewater treatment plants), sediments generated by storm-water, nutrients generated by application of fertilisers on agricultural land and wastewater finds its way into the lake. Sedimentation basins and wetlands are useful options for controlling sediments and nutrients. Wastewater treatment plants will treat wastewater to a level, where it can be used for irrigation of crops that are not eaten raw.

Shallow deposits of sediments impair good habitat quality and can be removed by dredging when water levels are low which will increase volumetric capacity of the lake.

Manchar Lake is facing problems of loss of fish life and retarded growth of fish. This is due to external stresses imposed by inflow of contaminants. Once, the inflow of contaminants is stopped, it would be necessary to assess and improve fish habitat.

Aeration of lake water and lake sediments through floating or submerged aerators will help increase dissolved oxygen levels of lake and remove anaerobic hot spots on the lake bed. Since Manchar Lake is a large water body, it would be costly to aerate its contents.

Manchar Lake is under the administrative control of the government of Sindh. The government has failed to develop policy framework for rehabilitating the lake. Policy framework is essential to develop programs, plans and a road-map for improving the lake's environment.