1. INTRODUCTION

Manchar is the biggest shallow water natural lake of Pakistan; situated at a distance of about 18 kms from Sehwan Sharif, district Dadu, Sindh. It is a vast natural depression flanked by the Khirthar hills in the west, the Laki hills in the south and the river Indus in the east. Flood bunds constructed in 1932 form its northern and northeastern boundaries. Indeed such a large natural body of fresh water is a major resource in an arid region.

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.

2. CHARACTERISTICS OF THE LAKE

The topography of the lake is such that in cold weather the Manchar may be only 2 Sq. miles or so in area at its lowest basin level RL 100-101. In past there has been years when the lake had dried up entirely. However, at the time of heavy rainfall the lake extends northwest with the result that it may cover an area of about 100 Sq. miles or nearly 64000 acres at RL 113. The area of lake has been restricted at higher levels by construction of Manchar Containing (MC) and the Flood Protective Embankments (Bunds). On the eastern side, MC bank joins the banks of Aral Manchar at mile 0 in the south-east and in the north-west links with the Flood Protective Bund at the out fall bridge of MNV drain. The length of the MC bank is 20 miles and is originally designed to withhold the water up to RL 116.

The lake was surveyed in 1964 and again in 1990. The data obtained from this survey is given in Table 1.

Table 1.

Manchar Lake: Stage-Area-Storage Data

This data indicates that considerable storage capacity has been decreased due to sedimentation at lower levels. This loss of storage decreases with increasing storage. From this table it can also be seen that the lateral expense of the lake is up to contour 113 feet above mean sea level (MSL). Beyond this, the lake rises vertically bounded within the periphery bund on one side and the hills on the other. The total area between the contour 107-113 is 23,318 acres. It is this area which the farmers desire to expose for cultivation during Rabi and it is under their pressure that the lake is drained off in the years when it is filled beyond RL 107.

Besides the agricultural losses the lake is subjected to evaporation and absorption losses. For the estimation of such losses no particular method has been evolved yet.

Inflow to the lake is very much erratic and unreliable since it depends on flood flows. Various methods have been adopted to increase inflow. Mean annual rainfall in this area is only 4.43 inches (112.5 mm) against evaporation of about 80 inches (2000 mm). Therefore, very little runoff is generated within catchments of hill torrents during dry or average years. Hence, the lake is recharged by this source only during wet inflows, which normally occur once in three years and have not occurred since last five years. In fact, there is no direct data on inflows and releases from the lake.

Manchar Lake receives its supply from three different sources. These are: Hill torrents, Inflow from River Indus and Main Nara Valley Drain (MNVD). Each one is discussed below.

3.1 Hill Torrents

The most significant hill torrent, which causes major flooding of the Manchar Lake, is Gaj. In the unprecedented heavy rainfall in the catchments of the Gaj in 1995, an ever-maximum flow of over 3 lac cusecs was recorded, which surpassed previous maximum flashy discharge of 170,000 cusecs, which lasts, may be, for few hours. However, the inflow from this source is erratic and unpredictable and has frequency of once in three years. In addition to Gaj, there are also some other small torrents such as Angai Nai, Nari Nai, Naing Nai etc. contributing towards Manchar. All these torrents are characterized by flash floods, which are quite difficult to gauge accurately. There are no actual reliable data for this source of supply.

3.2 Inflow from River Indus

Main source of fresh water for Manchar Lake is river Indus, connected with Manchar through three link canals. However, high flood flows in Indus have been substantially reduced by progressive upstream diversions. 13 years (1962-74) record of pre-Tarbela flow shows that actual supply through these channels remained 0.14 million-acre feet (maf), which was curtailed to mere 0.08 maf after the construction of Tarbela. Hence the construction of Tarbela has affected the supply of fresh water from Indus through gravity flow. The situation can grow worse with the construction of Kalabagh dam, having design capacity of 12 maf. Indus is connected through some old inundation canals namely Aral Manchar Canal (Wah), Aral Lakhi and Danister Canal.

3.2.1 Aral Manchar Canal

Aral Manchar Canal (Wah) has nominal capacity of 4370 cusecs, is the major source of filling Manchar form the river Indus, with its head regulator at the end of L.S Bund near Sehwan town. This regulator has two spans of 20-ft width each and cill level is at RL 100.

3.2.2 Aral Laki

Aral Laki has a nominal capacity of 7935 cusecs, is the most efficient low level canal with its primary purpose to drain-off the lake as and when required. In monsoon season it can effectively be used to fill up the lake also. The head regulator of this canal has three spans of 20-ft width each and is a double acting sluice with cill level at RL 98.0. The flow in this canal is limited due to confluence. The actual capacity of the channels at normal lake and river levels is significantly less.

3. Danister Canal

It is an old inundation canal revived after 1972, at the request of farmers, has design capacity of 500 cusecs. Danister canal is the most efficient and dependable source of filling Manchar with its downstream tail regulator up to the lowest basin of the lake. The canal out falls in Manchar through tail regulator having its cill level at RL 103.0. The head regulator level at RL 101.0 and canal bed level at RL 100.0 are so designed as to provide water to the farmers at low levels of the river.

Small pump stations have been installed on the Aral Manchar and Danister canals to augment flows at times of low river levels. They contribute only a small amount, can only operate when the flow downstream of Sukkur is more than 80,000 cusecs, since pump stations are not situated on the main river channel. Further, operation and maintenance of pump stations is quite costly and cumbersome due only to their occasional use.

2. Main Nara Valley Drain (MNVD)

The Main Nara Valley Drain (MNVD) runs between Hamal lake in the north and Manchar lake in the south. A schematic layout of the system is shown in the attached map. It was constructed in 1932 to provide drainage for rice effluent and storm water and also to pass Kachhi plain flows which were ponded at Hamal lake . The drain is 364 RD (111 kms) in length.

There are two main sources of supply from Right Bank to Manchar viz. Pritchard escape ex. Dadu Canal and Rawat Drain ex. Mehar Branch of Rice Canal system.

3.3.1 Pritchard Escape

This off takes at mile 95 of Dadu Canal. It is 18 miles in length and has its outfall in MNV Drain at RD 170 i.e. 40 miles north of Manchar Lake. This escape was designed for discharge capacity of 700 cusecs to be operated in emergencies on Dadu Canal. It has been proposed to make use of this already existing source for feeding Manchar.

The Rawat Drain takes off from tail of Mehar Branch ex. Rice Canal. It was originally designed for a discharge of 500 cusecs. This drain would be worked with great advantage for supplying water to Manchar. It is six miles long and has its outfall at a distance of about 60 miles in north of the lake.

Prior to this arrangement the drain was meant for conveying storm spillage of Hamal Lake to Manchar Lake. Hence MNV drain was initially meant for transporting fresh water to Manchar Lake. But construction of some irrigation and drainage projects in the upstream vicinity during 1970’s and 1980’s, started disposing off their saline effluent into Manchar Lake through Main Nara Valley (MNV) Drain. This particular source has accelerated the build up of injurious salinity in water quality.

3.3.3 North Dadu Drainage Project

This project is the main contributor of salinity in Manchar. The project is divided in four main catchments areas namely, Wagan, K.N Shah, Mehar and Ghar. Each of them pumps out its drainage effluent in the lake via MNVD.

Remodeling of MNVD (RD 0 to 343.5) has also been provided in Right Bank Out fall Drain (RBOD) project to enhance its capacity to accommodate the effluent from the project area.

4. USES OF MANCHAR

4.1 Agriculture

The water contained in Manchar Lake is predominantly used for agriculture. This water serves two folds from agriculture point of view. This includes:

• Since adequate supplies of water do not reach the tail of the Dadu canal from Sukkur Barrage, the lake water is diverted away through small canals known as phats for irrigation purpose. This water is pumped from the phats to irrigate potentially large areas.

• Cultivation on the lake floor as the water level recedes. Traditionally, this method relies on filling of the lake in flood season (monsoon), and then drawing down of the lake to uncover cultivable land on which wheat can be grown using the residual moisture.

For later type of agriculture, the lake should be filled to about 113.0 ft by the end of September and then reduced to 106.0 ft in October, thereby uncovering about 26,000.0 acres between 106.0 ft and 113.0 ft contours.

The level will then decline further, as a result of evaporation, before it can be refilled in the following year. This is not serious for the local agriculture but it has several other consequences:

• there is little stored water available for irrigation by phats;
• there is said to be too little water to sustain the fisheries;
• domestic water supply becomes saline and
• high level in Manchar allows a large area to be irrigated and reduces the pumping head.

4.2 Fisheries

Manchar Lake, fisheries are an even more complex issue. Since time immemorial, fishing has been the mainstay of the inhabitants of the area surrounding Manchar Lake. Nearly 10,0000 souls have been directly linked to fishing occupation, but have apparently declined in recent years due to poor conditions of the lake. Once recorded catch of about 3000 tons per annum in 1950, declined to just 300 tons in 1994 and presently dwindled to a terrible catch of hardly 100 tons. A survey conducted in 1930 revealed the existence of 200 species of fish, out of which 14 species are extinct. Thus the fishermen have been forced to look elsewhere for their livelihood due to paucity of fish in the lake. It is reported that about 40,000 inhabitants have migrated to other areas due to one or other reason associated to the degradation of Manchar Lake.

One reason for decline in fish is probably that the water level often drops below the minimum required for fisheries, generally accepted to be 104.0 ft. Indus water diversions on upstream coupled with increased inflow of saline effluent has resulted in the total devastation of the lake. It is only possible to fill Manchar when the river discharge is more than 80,000 cusecs. There is evidence that the date at which the river attains this discharge is gradually becoming later. Below given suggestions seem to be possible solutions to the problem:

• to fill the lake from the river earlier
• to stock the lake artificially

Manchar is the main source of domestic water for the communities living around the lake. Groundwater in this vicinity is saline and is not suitable for drinking. In years when the lake dried up completely, such as in 1980, tankers have supplied the water. Supply of contaminated water from Manchar has caused much resentment among the communities; particularly Sehwan town has witnessed a series of processions, strikes and rallies. The communities complain of sharp rise in stomach diseases, caused by the toxic supplies from the lake. Local administration is now seriously after some safe alternates to supply potable water to the residents.

4.4 Flood Protection

The inflows from the hill torrents from the Khirthar hills eventually find its way to Manchar. In most years, hill torrent flows are small, but occasionally very high floods occur, particularly from the Gaj Nai. These exceed the capacity of the lake outfall channel to the river at Sehwan, and must be attenuated by storage in Manchar if they are not to damage or destroy the FP embankments, harm agricultural lands or crops, drown Sehwan town and other neighboring villages.

In 1917, before construction of the FP embankment, a major flood of water level 119.0-ft occurred. This corresponded to storage of 1.5 MAF at that time. The most sever flood on record occurred in 1976. The lake level rose to cover 125.0 ft and damaged the FP embankments, which were initially designed for a flood level of 117.0 ft. This event was caused by an exceptional flood in the Gaj Nai estimated as 250,000.0 cusecs at Jubble, which coincided with high river levels of 120.0 ft causing a passive drainage from the lake. The worst was witnessed in 1995, when Gaj played havoc with the Kaachho area. Flood protection system sustained severe damage, which is not yet completely overhauled.

5. ENVIRONMENTAL DEGRADATION OF THE LAKE

With the onset of winter and the blowing of cold Siberian winds, migratory birds and waterfowls from regions north of Pakistan begin to move south in search of food and warmer weather. Manchar Lake used to be one of the major feeding and resting-place for these migratory birds. Both its large indigenous variety and the visitors created a breathing sight. People from across Sindh, other parts of Pakistan and many foreigners flocked to Manchar Lake to experience this magnificent sight. According to available statistics, in 1988 there were 25,000 waterfowls in Manchar Lake. The winter population was much higher. Today, the lake stands totally abandoned by its flying visitors and the indigenous population has also diminished considerably.

The story of fisheries is similar. Once recorded catch of about 3000 tons per annum, has now dwindled to just over 100 tons. Like birds, fishermen have been forced to look elsewhere for their livelihood due to paucity of fish in the lake.

Severe environmental degradation has visited this lake in recent years. Basically, three major factors have contributed to this tragedy:

1. Scarcity of fresh water
2. Build up of salinity with consequent reduction in nutrition
3. Rise of bed of the lake due to sedimentation.

The simple reason of environmental degradation of the lake is disturbed balance of fresh and saline intake. Two major sources of fresh water viz. Indus and hill torrents are virtually non-existent. Whereas the third one i.e. MNV drain is turned hostile to the lake. Imprudent fishing practices of fishermen community have also caused considerable damage. Fishermen use intoxicating chemicals to augment their dwindling catch. Villages situated in the lake body also dispose their solid and liquid waste in to the lake.

Manchar Lake is dying and the problem has accelerated in the last four decades particularly. In 1951 and again in 1974, the lake had dried up completely.

During 1989-91 lake water samples were collected at various locations and analyzed. These showed that the range of salinity varied from 500 to 4,000 parts per million (PPM) against desirable limit of 500 PPM. This has obviously reduced the level of nutrition in the lake necessary for sustenance of natural habitat. As per standard of World Health Organization (WHO), the maximum acceptable level for human consumption is 1500 PPM. Though agriculture has less stringent requirements, salinity above 1,500 PPM is hazardous. Requirements for wildlife and fisheries are somewhat less stringent but that aspect is not to be stretched too far, particularly as level of water in the lake is also an important factor.

Machar was gifted with numerous fauna comprising Acacia, Popla Sheesham, (Rose wood) Eucalyptus, etc. In addition to this many other of other trees and shrubs produced mystic and mysterious atmosphere.

Dense forest surrounding the lake hosted number of mammals such as fox, pig, jackal crested porcupine, rabbit, ‘chinkara’ hog deer, wolf, ibex and urial. Ibex and urial are only found in these forests within the frontiers of Pakistan. The surroundings were also rich in birds, which imparted an exciting exoticness to the area. Ducks, quails, swallows, cranes and numerous other birds fluttered and waddled splashing a myriad of colors in their trail.

The emergent reed (Tyohaangustata) is now the most widespread plant occupying the bed of the lake. Other emergent includes Juncos Articulates, Scripus Jittoralis and small patches of Phargmite Karka. Floating Water lilies and bottom-rooted plants including Nympaea now cover the water surface in place of the beautiful birds.

6. Water Quality of the Lake

Water monitoring reports clearly indicating an alarming pace of salinity buildup, which is a serious threat for very existence of the lake. The following table shows the trend of salinity rise in the lake. The data is borrowed from WAPDA, SCARP Monitoring Organization.

7. PRESENT STATUS OF THE LAKE

Lake regime has been changed by human activities over the last 50 years or so. These include reduced efficiency of channels linking lake to the Indus River; as a result of upstream diversions on the Indus. Consequently this has reduced the inflow from river Indus into the Lake. Moreover due to deterioration of water supplies at the tail of Dadu canal system, the agriculturists demanded irrigation supplies from alternate sources. In order to cater their demand Danister canal along with its distributaries (phats) was revived. Similar Phats were also provided at Aral Manchar canal also. This facility induced the farmers to intensive and extensive irrigation within the lake Periphery and outside through radiating phats by lift irrigation. Hundreds of lift machines are installed to take use of this water potential to the extent of emptying the lake to RL 103.0 against the RL 104.0, minimum required for survival of fish.

There have been complaints by local communities for conservation of the lake. To this effect a former Prime Minister decreed to protect the lake from its deterioration. This gives an indication of the political importance attached to the lake. However, very few practical steps have been taken in this regard.

Water shortages are a common problem and inevitably there are conflicting views on how it should be operated. To cope up with this problem at least partially, pumping stations have been constructed on Indus to fill the lake, but unfortunately they do seldom operate.

While providing economic impetus and additional irrigation water for agriculture at the upstream reaches of Indus have obviously brought negative factor for the lake. Over the years, degradation has grown into a threat for the very existence of the lake. However, the situation is not irreversible the problem can be cured.

8. CONCLUSIONS

Manchar Lake is nature’s gift to Pakistan and the world, therefore it needs to be preserved and protected. It lies in one of the most backward areas of Pakistan. In this area, there is practically no industrial or other activity to boost the socio-economic conditions of the area. Agriculture and fisheries are the main livelihood of this area. Due to increase in population and change in agricultural patterns, pressure on water potential has increased tremendously creating imbalance in demand and availability of irrigation water, particularly in this area as it is at the tail of Dadu canal system. People have been demanding assured water supplies for their various uses including irrigation. Manchar Lake being a natural depression forms a potential storage reservoir, which was originally free from pollution. Indeed due to mismanagement of water, the lake has been victim of degradation. Much of the culture created over centuries by the local population’s contiguity with the lake and its flora and fauna stands threatened by the multiple menace of salinity, sedimentation and low/inconsistent replenishment of water. All this has sunk Manchar Lake to extreme depths of despair. It is therefore obligatory to conserve this lake for the following basic objectives.

1. To provide assured supplies to about 26000 acres of cultivable land lying within the periphery of the lake between RL 106.0 and 113.0.
2. To ensure irrigation water supplies to approximately 46000 acres of cultivable area irrigated by lift irrigation on various phats.
3. To provide livelihood to a sizeable population of about 100,000 fishermen who have settled around this lake since time immemorial.
4. To create favorable conditions for livestock, which is the only source of income for their livelihood.
5. To mitigate the floodwater and to protect the neighboring settlements from inundation, by containing the torrential floodwater into the lake.
6. To maintain pollution free environmental conditions in order to provide a clean habitat to birds, fishes and animals, which had also attracted tourists and served as economic life line for the local population in particular and the country in general.

8.  
9. Recommendations

1. A comprehensive revised plan for rehabilitation and conservation of the lake should be prepared, with active participation of the local communities and experts. Participation of local fisherwomen in the plan should be ensured.
2. Inflow of saline effluent from MNV drain should be delinked from Manchar.
3. Fresh water flow from Indus should be enhanced and regularized by installing well-equipped pumping station.
4. The Sehwan barrage project should be implemented to convert the lake in a permanent reservoir.
5. Fishermen community, particularly fisherwomen should be trained to improve their fishing practices to ensure sustainable livelihood for them.
6. Diesel engine boats shall not be permitted for boating and fishing purpose. Their oil spillage also causes degradation of the lake. People shall be facilitated to get these boats replaced.
7. Lakebed should be desilted and deweeded. Villagers should be provided alternate arrangement particularly for solid waste disposal outside the lake body. Fisherwomen be provided trainings for maintaining better in-house environment.
8. Structures be constructed to channelize flash floods in Kaacho plain. Presently the lake receives only 25% of flow, rest is lost to evaporation and percolation. These channels would also be helpful in containing gushing floods in Kaacho.
9. All institutions working in the area for rural development, agriculture, irrigation, women development, drainage, forestry and fisheries should be reorganized, considering the new realities of Manchar Lake.
10. Water quality monitoring should be carried with more frequency and results should be made public.

9. LITERATURE REVIEWED

1. Jareeda, IUCN, April-June, 1999

2. Nasir Ali Panhwar, Sindh Goth Sudhar Sangat, "Right Bank Outfall Drain (RBOD) Project and its Implications", June 1998.
3. Water and Power Development Authority (WAPDA), "Report of the Panel of Experts on the Effects of Agricultural Drainage Discharge on the Quality of the River Indus", September 1996.
4. IPD Sindh, "North Dadu Drainage Project-Revised PC-I", 1996.
5. WAPDA, "Report of Technical Experts Committee for Disposal of Right Bank Outfall Drain Effluent", June 1995.
6. WAPDA, "Lower Indus Right Bank Irrigation and Drainage (RBOD)

Stage–I Project", November 1995.

7. Irrigation and Power Department (IPD) Sindh, "Brief Note, Restoration of 1995 Flood Damages to Gaj Diversion Bund".
8. Mott MacDonald International Limited & Hunting Technical Services Limited, "Supplement S1.4-Manchar and Hamal Lakes", February 1992.
9. IPD Sindh, "Conservation of Manchar Lake", 1989.
10. IPD Sindh, "Report on Manchar Lake", June 1975.
11. WAPDA, "Manchar Lake, A Case of Nature Abused Through

Humanity".

12. WAPDA, "Indus Link".