Water losses in agriculture – an alarming fact!

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The use of water for agriculture is 70 per cent of all the water used on the earth. Water has its great influence on reducing poverty than rural literacy. Increase in the selection high yielding varieties and the use of fertilizers help in decreasing poverty but their influence is lower than the impact of irrigation and rural literacy. When irrigation water is enough, the cultivation of high yielding varieties and fertilizers is also high. A better irrigation system is the first requirement of high productivity. Unfortunately most of the farmers are bereft of optimum quantity of water for irrigation due to two major reasons; lack of storage reservoirs and a major part of available water is lost during conveyance.

Most of the irrigated agriculture takes place in this area, which supports 65 per cent of Pakistans population. It is estimated that about 92 per cent of Pakistans land area is arid or semi arid areas. About 38 per cent of Pakistans irrigated lands are waterlogged. Only 45 per cent of cultivable land is under cultivation at a given time. Salt accumulation has also been occurred in the Indus basins.

The major crops of our country include wheat, rice, maize, sugarcane, cotton, sorghum. All of these crops require a regular supply of irrigation water. According to official statistics, deficit in grain production in relation to population is predicted to be 12 million tons. Water availability went down to 1500 m3 in 2002, making Pakistan a water-stressed country. It is now increasing day by day and will reach its alarming limit up to year 2035. According to UNEP, Pakistan is among the most one of the worlds most fresh water-stressed countries. Water and food security are Pakistans major issues this century.

Saline water intrusion is observed into mined aquifers. Pakistans glaciers are expected to melt by 2035, according to Zahid Hamid, Federal Minister for Science and Technology, and it will have a disastrous effect on fresh water flows. Being an agro-based economy, Pakistan is extremely vulnerable to climate change as the sector contributes 21 per cent to GDP. Pakistan loses 13 million cusecs of water every year into the sea while seawater encroachment damages land up to 100 kilometres of cultivable land during periods of reduced river flow – for a country that uses nearly 90 per cent of its water resources for agriculture and depends on the sector to remain buoyant, this is a dangerous trend.

Irrigation water losses include air losses, canopy losses and soil and water surface evaporation, run off, and deep percolation. The magnitude of each loss is dependent on the design and operation of each type of irrigation system. River Indus and its tributaries supply 154 MAF of water annually: the Westerns Rivers contribute 144.91 MAF of water while the eastern rivers bring 9. 14MAF. Of the 154 MAF, 104.73 MAF is used for irrigation purposes, 39.4 MAF flows to sea and about 9.9 MAF is lost to seepage, evaporation and spill during floods. With the increasing pollution owing to inadequate sewage disposal systems and dumping of industrial and agricultural waste, the quality of surface water is deteriorating. The effects of pollution are not just limited to surface water – groundwater is equally threatened by it. Already about 36 per cent of groundwater is classified as highly saline due to salt intrusion and excessive mining has caused water tables to fall.

Groundwater now accounts for half of all on farm irrigation requirements (supplementing the 34 MAF of surface water that actually gets to the farm lands). Groundwater irrigation has been rapidly developed by the private sector. Groundwater quality accounts for higher variability.

Long-term use of groundwater can lead to secondary salinization. The awareness of mixing ratios that can sustain the irrigated agriculture in the long run is normally lacking. Pakistan is using 97 per cent of its surface water resources and mining its groundwater to support one of the lowest productivities in the world per unit of water and per unit of land.

It is also threatening situation that the water storage capacity is very low at only 150 m3 per capita per year only 30 days of supply. Two major dams Mangla and Tarbela have lost 25 per cent of their storage capacity. Canals also work on rotation and do not flow throughout the year for a constant supply of water. The water losses between canal heads and farms are 2/3.

River Indus downstream from Kotri Barrage has virtually dried out. Also only one out of 17 main creeks of Indus Delta is now active remaining in a very poor condition. Balance between seawater and fresh water in the tidal zone has been disturbed badly. Sea water intrusion has been reached to 225 kilometers.

In Pakistan, it is partially recognized that water has its economic value. Irrigation and domestic water costs are very low and people roughly use excessive amounts of water. There are no proper drainage systems regarding safe disposal of water. While the realities of water availability, water regime, climate and delta conditions have changed, the demand for more and more water for agriculture continues to grow in most parts of Pakistan.

Discourse needs to be redefined in terms of head, middle and tail farmlands in irrigated areasWater other than agriculture – for domestic use, for industry, for urban areas, and for the environment – should all be key components of discussion.

Pakistan does not have a comprehensive set of water laws that define water rights, uses, principles of pricing, subsidies, conservation and polluter penalties.

Few recommendations for efficient use of water are agro-climatic zoning, division of Indus basin into its sub-regions and targeted long-term water strategy and programming for each, changes in agricultural practices, more crop per drop technologies, policy issues should favor water usage, micro irrigation techniques where feasible, rehabilitate existing irrigation infrastructure and better maintain it, improvement in water quality, water quality standards and control of water pollution from all sources, aggressive promotion of water conservation, measures to rehabilitate the freshwater-seawater interface on coasts, adaptation to climate change, use of mulches, implementation of effective tillage practices and use of anti-transpirants like Hydroxylamine hydrochloride, Phenyl mercuric acetate (PMA) etc. Successful adoption of these techniques and measures will not only reduce water loss but will make the irrigation system more efficient regarding water usage.

The authors are associated with the Agro-Biology Lab, Department of Agronomy, University of Agriculture, Faisalabad, Pakistan.


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Published in: Volume 05 Issue 36

Short Link: http://www.technologytimes.pk/?p=12016