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Tuesday, 02 February 2010 09:57 |
The Alluvial Aquifer of the Indus Basin: Its systematic degradation threatens desertification and eventual extinction
The Indus drainage basin covers an area of about 360,000 sq. miles in the eastern part of Pakistan. It comprises the mountainous catchment in its northern and western part, a desert tract in the eastern part, and a vast alluvial plain in its southern and central part. The Indus plain is underlain by a vast alluvial aquifer, the Indus alluvial aquifer. In Punjab it covers 25 m. acres. In Sindh it forms a relatively narrow groundwater artery about 350 miles long. The entire aquifer constitutes one unified hydrological entity.
This paper briefly summarizes the hydrogeology, groundwater potential, water quality of the aquifer and its Impact on the prosperity and future of Pakistan. Presently more than 90% of the aquifer is saturated with approximately 3500 MAF of water with an exploitable potential of about 700 MAF. This is about 50 times greater than the existing surface storage of about 14-15 MAF. However, the crux of the problem is that the aquifer contains large bodies of saline groundwater underlying nearly 50 % of the areal extent of the aquifer. Presently on an average 145-149 MAF of surface water enters the Indus plain annually and about 6% (6.36 MAF) is estimated to provide recharge to the aquifer. On the other hand annual ground water extraction from the aquifer is estimated at about 45 MAF. Extensive groundwater mining is thus taking place in many areas.
The present irrigation system has resulted in extensive water logging and salinisation. Reclamation activities have once again altered the hydrologic trend and through vast areas were reclaimed through tube wells, but it resulted in depletion of groundwater storage, extensive saline water encroachment and creation of serious problems of salt dispersal and concentration.
Spread over more than fifty years, our efforts to contain the water logging and salinity have not succeeded. New problems such as salt water encroachment, increase in soil and water salinity and rapidly falling water table have occurred. In other areas water logging is spreading fast and the net result is that despite reclamation of vast areas in upper Indus plain, we still have 38% of the area water logged and 14% of area severely salinised. Thus in effect the process of desertification has become effective.
Urgency of prompt action is highlighted by the fact that over the past 20 years available water supply has fallen for short of the requirements. We have survived mainly though enhanced groundwater extraction (presently 45 MAF annually). With growing population, a water shortage of about 40 MAF by 2005, 107 MAF by 2013, and 202 MAF by 2025 is expected. With insufficient surface water, groundwater was our only hope. But in view of above fact, it is difficult to foresee how the Indus alluvial aquifer can meet a short fall of 200 MAF by the year 2025. This picture is so gruesome that it warrants immediate attention of all concerned and action at a iwar footingi.
Author(s):
A.H.Kazmi, FF2, Block 59, Seaview Township, DHA, Karachi.
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Last Updated on Tuesday, 02 February 2010 12:22 |
