Global warming will reduce about 40% of Pakistan's surface Water

Global warming and glacial melting is life threatening climatic change and environmental calamity on earth. It would imbalance and adversely change water cycle on earth affecting irrigated agriculture. Unfortunately, Pakistan is located in a region that would be worst affected by global warming. Its agriculture is already water stressed and suffers due to shortage of water, increasing soil salinity due to lack of surface and sub­surface tile drainage and the massive use of 45 maf of injurious saline drainage effluent as groundwater for irrigation. Pakistan has the world’ largest contiguous canal irrigation system in the world and about 70% of its population are engaged on irrigated agriculture. Water is the basic and vital input of agriculture but is scanty and highly mismanaged and ill planned like power generation.

The global warming and glacial melting would drastically reduce surface water of about 142 maf by about 40% or 52 maf in the supply-based canal irrigation system. This means the available 142 maf of water would reduce to about 90 maf. This 90 maf of water diverted in canal system is again subjected to 50% water wastage in the 150 years old, incompatible, seeping and obsolete supply-based canal irrigation system. Therefore, net water available to crops would reduce to only about 45 maf. Out of this, about 10 maf of water is consumed by the 30 crores of population by the year 2040 besides the industrial use. The water left for crops at the field would be 35 maf. This scanty and small quantity of water would only cover  irrigated area of about 25% in the Indus basin. The remaining 75% of canal irrigated area would have no water. This means the whole of Sindh and half of Punjab would become desert due to lack of water. Therefore, all water wastage must be avoided, as water reduction due to global warming would be un-reversible calamity.

In spite of such water crisis, toxic effluent from industrial waste and cities are disposed of in Pakistan's rivers, streams and canals water as there is no arrangement for the treatment and disposal of toxic waste. The polluted canal water would produce poison containing crops, vegetables and fruits grown on poisoned land, and contaminate the surface and sub-surface water for drinking. As a consequence, it would cause starvation due to famine, death, heat, thirst, diseases, disputes and large-scale population migration.

Global warming has no quick and cheap remedy, therefore the Government is advised to pay serious attention for its preventive measures to minimize its severity. This is direly essential as population by the year 2040 would be doubled to 30 crores and surface water reduced to 35 maf to cover 25% of the existing irrigated area.

The only hope to increase the availability of water is to save most part of the 45 maf of water lost due to seepage in the 150 years old,  obsolete, wasteful and incompatible supply-based canal irrigation system. The quantity of water for irrigation in the Indus basin can therefore be increased by modernizing the supply –based irrigation system by saving water lost due to seepage.

It is direly essential to replace the supply-based system with the demand based canal irrigation system as part of integrated comprehensive water management (ICWM). The demand based canal system, storage dams like Katzarah, drainage system and efficient use of water through sprinkler and drip irrigation methods on healthy land are vital components of ICWM. The ICWM would save about 45maf that is wasted due to seepage in canal conveyance system. In this way the total water available at the farm gate would be (45+35)=80 maf. Deducting 10 maf for population consumption and industrial uses, the balance comes to 70 maf. The 70 maf of water must further be used by sprinkler and drip irrigation methods to cover 2 to 3 times more area than by flood irrigation. Sindh province may hope to use seawater after de-salinization.