Availability of water through efficient water management is the main right path for crop production

By Dr. S. M. Alam
Nuclear Institute of Agriculture,
Tandojam, Pakistan
Apr 16 - 22, 2001

It is surprising to note that 362 million kilometers or 71% of the global surface is water. The uses of water are numerous and life without water is impossible. A person can live without food for longer than he can without water or air. Given that 80 per cent of all life forms are found under the oceans. It has been estimated that agriculture used 47% of the fresh water available or about 200 billion litres a day. Water feeds plants and irrigates lands, allowing farmers to produce crops. Industry accounts for 40 per cent of all fresh water use. Industry uses water to transport goods, cool machinery, dispose of waste as power source and refining of natural resources. An example of industries huge water can be seen by the amount of water, it takes to make steel for one washing machine, which is 1,5000 litres.

Water is the earth's most distinctive constituent, natural resource and is an essential ingredient of all life. Its deficit is one of the most common environmental factors limit crop productivity. Most of the water in the hydrosphere is salty and much of the fresh water is frozen. It has been estimated that oceans all over the world contain about 97% of the planet's water, seven continents of about 2.8%, and the atmosphere about 0.001%. Similarly, about 77% of the water associated with land is found in ice caps and glaciers and about 22% is found in ground waters, much of which is uneconomical to retrieve. This scenario leaves only percentage of readily manageable fresh water as a resource of the water supply for the population. Plants transpire about 100-300 times more water during the assimilation of CO2 than is required for their growth and the production of a usable yield. It has been estimated that 600 kg of water is transpired to produce 1 kg of dry maize, and to produce 1 kg dry biomass, normally 225 kg of water is transpired. It was further reported that to produce 1 kg of sucrose, sugar beet plants transpire 454 kg of water, and to produce 1 kg dried biomass, they transpire 230 kg water. The world's land surface occupies about 13.2 x 109 ha, of which 7 x 109 ha is arable; only 1.5 x 109 ha of which is cultivated land. The cultivated lands, about 0.3 x 109 ha (23%) is saline and another 0.56 x 109 ha (37%) is sodic. Although, the data are tenuous, it has been estimated that one-half of all irrigated lands (about 2.5 x 108 ha) are seriously affected by salinity or water logging.

Availability of water through efficient water management is the main right path for crop production. The Indus basin irrigation system encompasses the Indus river and its three major water storage reservoirs, 19b barrages/headworks, 12 link canals, and 43 canal commands. covering about 90,000 villages/chaks. It covers about 39,000 miles. The three major reservoirs, Mangla, Tarbela and Chashma were built by Pakistan on signing the World Bank sponsored Indus water basin treaty between India and Pakistan. Irrigation in this country depends on both surface and underground water resources. The quantum of water entering the rivers aggregates to about 145 million acres feet per year. Of this about 110 million acres feet is transferred to canals for irrigation annually (72 per cent) and remaining 35 million acres feet flows down into the sea, because of lack of storing facilities. The quantum of water entering irrigation water courses from the canals amounts to 98 million acres feet per annum. Water obtained from 480,000 public and private-tubewells for irrigation purposes has been estimated at 45 million acres feet annually. Thus, the total quantum of water entering the water-courses both from canals and tubewells aggregates to 122 million acres feet annually. Of the 145 million acres feet water entering the canals each year, about 28 million acres feet (i.e. one fourth) is lost in transit due to a number of factors. Besides, about 40 million acres feet (i.e. 40 per cent lost within the water courses themselves). Thus, only 73 million acres feet water reaches the field. Also, about 18 million acres feet water is wasted in the fields. Taking into account all the losses as indicated above, only 55 MAF water is normally left for the irrigation of crops. While, 90 MAF water annually goes wastes. Thus, the wastage comes to about 62 per cent. The farmers normally need 3.5 MAF water per acre for cultivation, our crops get only 1.5 MAF water per cent.

The magnitude of the problem can be gauged from the fact that the area of productive lands was being damaged by salinity at a rate of about 40,000 ha / year at one stage. However, according to WAPDA authorities, it has not only been checked but also reversed and at present the reclamation rate is 80,000 ha per annum. On one hand, our land resource is subjected to a great threat from salinity and water logging. While, on the other hand, our population is increasing at a very fast rate of 3.0% per annum. It is expected that our population will grow to 150.1 million in the year 2001 and we shall need at least 40-80% more wheat, edible oil, sugar, milk and wood products at the present rate of consumption.

The two central dilemmas facing agriculture in Pakistan are limited amounts of water for irrigation, and increased salinity. The water budget shows that of the 145 million acres feet of water, which flows annually in Pakistan's rivers, only 12 million acres feet reach the farmer's fields. This figure is supplemented by a further 14 million acre feet of effective rainfall, and 45 million acres feet from tubewells. Leakage of canals and inappropriate irrigation practices have resulted in large increase in water tables in many areas of Pakistan. As a result of this, the Indus plain now has 6.3 million hectares of salt affected land. Both salinity and water logging are the twin menace for the agricultural productivity of the country.

The northern regions of Pakistan are full of world's largest glaciers. They are almost at the height of 4720 meters above the sea level. They form the biggest function of glaciers on earth giving birth to a pool of snow lake, in the surrounding of mountains. The Himalayas, the Karakorams, the Hindu Kash and the Pamirs in the north of Pakistan gave birth to the thickness of and the most amazing duster of the highest peaks and largest glaciers in the world away from the Polar regions. The valleys of mighty Karakorams to the west of Himalayas are more than 1500 square miles. About 37 per cent of the surface area of Karakoram is under glaciers as compared to 17 per cent of the Himalayas in Nepal, India and China put together and 22 per cent of the European Alps. There are also about 3000 small glaciers and tributaries. The hundred miles of cool, rush, splashing and scintillating winnowing torrents gushing out of the bullies of these glaciers mingle together to form about 3180 kilometers long Indus river, which flows the plains of Pakistan into Arabian sea near Karachi.