IRRIGATION CANAL SYSTEM IN PAKISTAN
Research Analyst, PAGE
Aug 30 - Sep 05, 2010
Pakistan has the largest contiguous irrigation system in the world which commands an area of 42 million acres. The Indus River and its western tributaries on an average bring about 142 million acre feet (MAF) of water annually and the average annual canal withdrawal is 104 MAF.
The system has three major reservoirs, 19 barrages, 12 inter-river link canals, 45 independent irrigation canal systems and more than 110,000 water courses. The total length of the canal system is about 64000 km. The system also utilises an estimated 42 MAF of ground water pumped through more than 921,229 tube wells (mostly private) to supplement the canal supplies.
Pakistan needs more water. There is less likelihood that new water storage projects could be completed in next 3?4 years. The country is dependent on its water infrastructure, and it has invested in it massively. The natural state of heavily-silt laden river Indus seeking lower lands and changing courses creates havoc with human settlements. Such rivers have been trained and confined by embankments within relatively narrow beds.
Overtime the likelihood of embankment breaching increases from floods.
The Indus Basin is a single, massive, highly complex interconnected ecosystem, upon which man has left a huge footprint. When a dam or barrage is constructed the water and sediment cycles are changed dramatically. When water is diverted onto deserts, the water and salt balances seek new equilibriums. The investment in building knowledge base and the accompanying institutional and human systems is key to efficient operation of the massive irrigation works.
Water is essential for sustenance of life in all forms and fresh water is a finite resource, progressively becoming scarcer due to persistent increases in its competing demands. Indus Basin Irrigation system includes three large reservoirs (Tarbela, Mangla and Chashma), 23 barrages/ head works /siphons, 12 inter-river links and 45 canal commands extending for about 60,800 km to serve over 140,000 farmer operated watercourses. Irrigated agriculture is the backbone of the national economy. The level of agricultural production is directly related to the availability and effective use of water as a major input. The demand for water is increasing rapidly while the opportunities for further development of water resources or maintaining their use to existing levels are diminishing. The shortage of water particularly in Rabi season has further aggravated the ongoing water crisis.
PER CAPITA WATER AVAILABILITY
YEAR POPULATION (MILLION) PER CAPITA WATER AVAILABILITY (M3) 1951 34 5260 1961 46 3888 1971 65 2751 1981 84 2129 1991 115 1565 2002 139.5 1282 2010 167.7 1066 2020 195.5 915 2025 208.4 858
Pakistan has an average rainfall of 240 mm a year. According to the benchmark water scarcity indicator, Pakistan's estimated current per capita water availability of around 1,066 M3 places it in the "high water stress". The water shortage scenario is further aggravated with high variability of the rainfall. The onset of climate change and global warming is likely to severely affect the availability of water. To aggravate the situation, after the loss of three major rivers: Ravi, Sutlej and Beas, to India under the Indus Waters Treaty 1960, India's construction of water storage infrastructure at Baghlihar and Kishanganga is threatening to disrupt the uninterrupted flow of water downstream into Pakistan.
Compounding lower availability is the issue of inadequate water storage. Pakistan stores around 40 per cent of the world's average in terms of storage. In comparison, the storage capacity of Colorado is 497 per cent, Nile 347 per cent, India 33 per cent, while Pakistan has just nine per cent storage capacity. As population size increases, resources become scarce in terms of per capita. The current per capita water availability at 1066 m3/person is low, with Pakistan in the category of a high water stress country, which requires concentrating on water resource development, urban and rural water supply and sanitation, industrial water supply, irrigation and drainage, hydropower and environment protection.
Groundwater under the Indus Irrigation System is plentiful and is derived from infiltration of surface water as well as local rainfall. However, depending upon the quality, the useable groundwater is confined to an area of 10 million hectares. The development of this resource is through private tube wells and accounts for a gross abstraction of about 40 MAF per annum. The surface water and groundwater and all canal commands are being used in conjunctive environment. In many canal commands, pumpage is greater than recharge thus causing subsidence. There is no regular and proper monitoring of private tube wells capacity, their pumping hours and utilisation.
It is important to ensure water security for the people through a national water policy laying down the outlines of an integrated water management strategy that aims at maximising the sustainable economic, social and environmental returns on the water resource development.