ABSTRACT
Water is a key input to agricultural production because its efficient and uniform application also affects efficiency of other inputs such as fertilizers. Water availability, however, in Pakistan has decreased from 5600 m3 in 1950 to less than 1000 m3 per capita, placing it on the list of water scarce countries as well as threatening its food security. One of the main reasons is limited water storage capacity of the country, which is only 10% of its river flows as compared to 33% in India, 281% for the river Nile, and a world average of 40%. This is also letting annually about 35 MAF (million acre-feet) of water flowing to sea. Whereas irrigation systems in the country also accounts for water losses; about 44 MAF of water are lost in canals out of the 104 MAF diverted from rivers. Out of 60 MAF of surface water supply available at the farm gate, only one-third of it is utilized by crops and the remaining is wasted as evaporation and deep percolation losses. These water losses and shortages have forced farmers to pump groundwater, resulting in its overexploitation of about 50 MAF annually through 1.2 M tube wells in the country. This groundwater abstraction is causing 1–2 m depletion of groundwater level annually and inducing secondary salinization problems. The water table in some areas, however, has started rising to waterlogging conditions due to heavy irrigation applications, as well as climatic and topographic effects. Moreover, water productivity in the country, that is, 0.45 kgm−3 for wheat, is much lower than that of 0.8 and 1.0 kgm−3 in India and the United States, respectively. This indicates the potential for improving water use efficiency through improved irrigation techniques. In addition, checking conveyance losses in the irrigation system and enhancing water storage capacity are imperative to meet the growing food and water demands, as well as to regulate the high seasonal differences in river flows under changing climate scenarios.
