WATER RESOURCES DEVELOPMENT AND MANAGEMENT
The Present Situation
The achievement of Water Vision is dictated by a consideration of the present position and how the present initiatives need to be channeled to achieve the desired objective. In respect of Water Resources Development and Management, the position has therefore been characterized, as a starting point, in the following section.
Available Water Resources
The water resources available to the country are the natural precipitation, the surface water and the groundwater. In the arid to the sub-tropical climate of the country, the natural precipitation is scanty. Over half the country receives less than 200 mm of annual rainfall, and rainfall in excess of 400 mm occurs only in about 20 percent of the northern areas. Apart from being scanty, the precipitation is distributed quite unevenly over the season and in a major part of the country this is concentrated in the 3 to 4 months of the summer monsoon. Despite its meager amount, rainfall is utilized for rain-fed agriculture and for meeting the drinking water needs of the people and livestock and contributes to the livelihood of a small but vulnerable portion of the population.
The source of surface water available to Pakistan are its rivers. Most of these rivers in the western half of the country, are ephemeral steams that remain dry for most of the year. It is the Indus river and its tributaries with perennial flows, that constitute the main source of water supply.
The Indus and it tributaries, have their sources in the Himalayan mountain and the Hindu Kush, with a total drainage area of 944,569 sq km, which extends beyond the country's territorial limits. The inflow to these rivers mainly derived from snow and glacier melt and rainfall in the catchment areas. The tributaries of the Indus, originating in India but flowing into Pakistan are the Jhelum, Chenab, Ravi and Sutlej (with a major tributary Beas). Originating in Afghanistan, the other major tributary is the Kabul River.
Under the Indus Waters Treaty 1960, the flows of the three Eastern Rivers, (Sutlej, Beas and Ravi) have been allocated to India, whereas with minor exceptions, Pakistan is entitled to all the water of the Western Rivers (Indus, Jhelum and Chenab). The average annual inflow of the Western Rivers at the rim stations (the most important gauging stations enter the Indus Plains is 172.70 BCM (140 MAF). This constitutes the main source of water supply for the country.
Although the surface flows of the Indus rivers and its tributaries available to Pakistan are quite significant these, are characterized by a great variation. Against the average annual inflow of 172.70 BCM (140 MCF), the long term historic data from 1922-23 to 1996-97 indicates a high of 230.42 BCM (186.79 MAF) or 30% below average in 1974-75. Apart from the large annual fluctuation, there is a large seasonal variation in these flows as well. The inflows during the six months of the summer cropping season of Kharif average 142.09 BCM (115.18 MAF) while the flows in remaining six months of the Rabi Season are 27.21 BCM (22.06 MAF) or only 16% of the average annual.
The quantity of surface waters in the Indus and its tributaries is excellent from all point of view. At the rim station the waters have total dissolved solids (TDS) ranging from 100 to 200 ppm and they do not represent any sodicity hazards. Although over the years drainage waters have been discharged into the rivers, the quality of the water even at the Kotri Barrage which is the last diversion point on the Indus, is characterized by a maximum value of TDS between the range of 150 and 350 ppm.
In addition to the surface water, groundwater is another important source of water supply. Investigations have established the existence of a vast aquifer with an areal extent of 194,000 sq. Km (74,904 sq mi) underlying the Indus Plains which has been recharged in the geological times from natural participation and river flows and more recently by the seepage from the canal system. Although the quality of the groundwater in the Indus Basin aquifer is highly variable, both a really and with depth, it is estimated that 67.85 BCM (55 MAF) of groundwater representing the safe yield, could be withdrawn annually for beneficial uses.
Outside the Indus Plains, the availability of groundwater has also been investigated through extensive sub-surface exploration and it has revealed the presence of useable groundwater in limited quantities in alluvial fans and valley aquifer.
The quantity of surface waters in the Indus and its tributaries is excellent from all point of view. At the rim station the waters have total dissolved solids (TDS) ranging from 100 to 200 ppm and they do not represent any sodicity hazards. Although over the years drainage waters have been discharged into the rivers, the quality of the water even at the Kotri Barrage which is the last diversion point on the Indus, is characterized by a maximum value of TDS between the range of 150 and 350 ppm.
In addition to the surface water, groundwater is another important source of water supply. Investigations have established the existence of a vast aquifer with an areal extent of 194,000 sq. Km (74,904 sq mi) underlying the Indus Plains which has been recharged in the geological times from natural participation and river flows and more recently by the seepage from the canal system. Although the quality of the groundwater in the Indus Basin aquifer is highly variable, both a really and with depth, it is estimated that 67.85 BCM (55 MAF) of groundwater representing the safe yield, could be withdrawn annually for beneficial uses.
Outside the Indus Plains, the availability of groundwater has also been investigated through extensive sub-surface exploration and it has revealed the presence of useable groundwater in limited quantities in alluvial fans and valley aquifer.
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