BALOCHISTAN is by far the largest in size but shelters smallest number of inhabitants among the four provinces of Pakistan. Topographically, it is subdivided by high to moderately high mountain-range, limiting accessibility. Climatic conditions are arid, ranging from dry to hyper dry and temperature regimes vary widely from cool to tropical. Only about 2 per cent of it is cultivated at any time due to the scarcity of water.

Balochistan is presently getting water from the Indus system, but less than its actual share for want of capacity, as there is only one canal irrigating the province. Although ‘kutchi’ canal project for Balochistan has been approved by the Planning Commission but its cost and date of start has not been fixed up as yet.

The vast area of Balochistan has always been viewed as a big potential for overcoming the food crises in the country but planners fail to judge that the amount of arable soil does not limit agricultural production but it is the availability of water.

Unauthenticated estimates obtained by crude calculation that over one million acre feet of flood water flows down to the Arabian Sea from mountainous range of Balochistan have prompted WAPDA to prepare a plan for building a series of dams notably Mirani and Hingol to bring about green revolution in the province.

Historically, the word “dam” has always been a debatable term in Pakistan as dams were judged and constructed on political basis rather then technical basis. For instance, Kalabagh dam was conceived and to be constructed prior to Tarbela dam. But the then government kicked off Tarbela dam prior to Kalabagh dam that has since then become controversial. Similarly, bids for Mirani dam were sought in 1995, but due to certain political reasons, the dam was replaced with Hingol dam in 1996. The present government managed to hold the ground-breaking ceremony for Mirani dam last year to mark the beginning of Wapda’s water resources and hydropower development under Vision-2025 programme.

Mirani Dam is located on Dasht river, about 48km west of Turbat town in Mekran division. The 127 feet high dam was estimated to cost over Rs5 billion. It would be funded by the federal government and Wapda. The life of the reservoir has been worked out about 30 years.

The physical work includes construction of 3,350 feet long earth-fill dam with a gross storage capacity of 0.302MAF with annual release of 0.114MAF. The power generation aspect (3.1 Kwh per annum) of the project will be examined in detail to determine economic feasibility of generating hydroelectric power at this project as compared to other available alternatives.

The Dasht is a non-perennial stream whose flow depends on rainfall in the catchment area, which is spread over 7,960 square miles of hilly terrain, mostly devoid of vegetation. The average annual rainfall for the catchment is 4.2 inches. The average annual run-off from the catchment has been estimated to be 226,000 acre-feet. The total sediment load per year flowing into the reservoir would be of the order of 7,000 acre-feet.

Hingol Dam Project will cost Rs21 billion with a foreign exchange component (FEC) of Rs1.9 billion. The multi-purpose project envisages uplift of the local economy by providing irrigation and drinking water and generating electricity. The gross storage capacity will be around 0.97 MAF. The command area to be irrigated will be 9.250 acres.

The feasibility report of the Hingol dam shows that the life of the reservoir would extend over 60 years on the basis of hydrological data. About 5 million gallon daily (MGD) of water has been planned for the use of Hingol port and industrial area. Moreover, power equivalent to 300 KW of installed capacity will be generated for this power-deficient region.

The possibility of exporting about 115 MGD surplus water to the UAE has also been planned but if the government decides not to export water, then it would be used for irrigating an additional area of 50,000 acres of land in Balochistan, besides providing drinking water to Karachi for meeting its growing demand, through 145 miles water pipeline from the dam site.

Flood-water may represent the only untapped water resource of considerable potential; however the base flow water from small rivers and the ground-water are nearly completely exploited in Balochistan. Flood-water is the unknown resource in term of amounts and especially frequency. In the absence of an automated monitoring network for floods and rain, execution of such mega projects creates certain doubts.

As such, there must be rigorous hydrological analysis from year to year basis for a realistic estimate of the benefits to be derived for the people from the Mirani and Hingol Dam projects. Hydrologists, however, suggest that the hydrological parameters of the feasibility should be reviewed. They express serious doubts about the availability of water during the periods of drought, which at times persist for more than five years.

Rainfall maps in Pakistan, including Balochistan, represents mostly a hypothesis rather than facts. Such maps are based on point measurements that are extrapolated to isolines or overmapping areas mostly by unverified models. Consequently these maps are of limited practical value as far as agricultural development is concerned.

The precipitation figures obtained by such means are probably under-rated. Precipitation averages are meaningless in arid zones if taken as absolute figures. Wet and dry years tend to come in clusters. Within a year the spatial variation within each rainfall zone may be larger than the average year-to-year variation of the entire province.

The summer rains in Balochistan are heavy, erratic and have short duration which produce instantaneous, heavily silt-laden runfoff. Vegetation degradation has caused accelerated and increased runoff. Flood irrigated agriculture is found through- out Balochistan wherever terrain permits. In most cases, traditional structures are used to divert the floodwater onto lands.

Flood-water diversion schemes have been built extensively during the last decades to divert water to the valley floors. Most of the diversion schemes have not survived longer than 3-5 years and Balochistan is littered with the ruins of unsuccessful diversion structures. The failure of the structures is mostly attributed to design error in the engineering structure by under-estimation of the silt load, Farmer’s interference with the flood-water diversion to make maximum use of the water in agriculture and systematic under-estimation of peak flood discharge resulting in the destruction of the structure.

Artificial ground-water recharge with floodwater was also attempted by the construction of delay-action dams. These are located just within the hills where the river enters the gravelly fan. The reservoir is situated on the river alluvium in the transition zone to the fan. The temporarily stored floodwater was supposed to infiltrate and percolate to the ground water. Unfortunately the action-delay reservoir floors silt up rapdily such that the delayed action became indefinite leaving the water to evaporate rather than infiltrate.

Enhanced sedimentation in Balochistan has already caused failure of reservoirs, delay-action dams, irrigation channels and other control structures. It is likely to shorten the exaggerated expected life of Mirani and Hingol dam as well. Shortened lifetime of these dams can be prevented but at a very high cost of maintenance which we can’t afford.

No doubt that Balochistan is in the dire need of water-related development but it must be done after a comprehensive analysis and study of reliable data. We, as a matter of fact, are not technologically and financially on a leading edge, therefore we must not waste our valuable resources and financial assets in doing experiences, rather we need to learn from mistakes of other nations. There are certain examples around the world when dams having barren catchment areas producing silt-laden runoff ended in failures.