The present water distribution system needs modification

By Dr. S.M. ALAM and Dr. R. ANSARI
May 21 - Jun 03, 2001

Pakistan, with a total geographical of 79.61 mha and the 8th most populated country, has the largest canal system in the world. In Pakistan, out of the total cultivated area of about 20.43 million hectares, 14.75 million hectares is canalling watered, whereas tubewells are providing water to 4.29 million hectares. The barren area constitutes 20% of the total cultivated area. Agriculture is the largest sector of Pakistan economy that is why, agriculture is called the backbone of Pakistan economy. The contribution of agriculture towards gross domestic product (GDP) and gross national product (GNP) increases gradually because of the new technologies. Though, these new technologies have gained substantial popularity and practicability and have achieved some meaningful results of progress, but have not so far reached its optimum level. Though the rate of return in agriculture are lower, yet this sector must continue to supply food and fiber for ever increasing population of Pakistan to combat with the food problem in the country to face the crisis of unemployment to create markets for consumer's goods to supply raw material for industry and to earn foreign exchange for the developing economy of the country by exporting surplus of agricultural products. The importance of agriculture in our national economy can be judged from the fact that about 50% of our civilian labour force are directly or indirectly involved in agriculture. About 50% of foreign exchange are earned by agriculture based commodities.

Water, as the most precious natural resource, has to be properly managed and utilized to sustain life and well being. It is a premium of life. The uses water are numerous and life without water is impossible. Water is one of the human body's primary and basic need, so much so, a man go on living for upto 80 days or more without food, but it will be almost impossible for him to live, if he is not given water for more than two days. An average a person in an underdeveloped country uses 45 litres water per day. About 45 kg of water is replaced by our body a number of times in a year. In industry, also water is considered as one of the most important commodities. It serves in many industrial plants as process and utility water and is the dispensable stem boiler feed. Industry accounts for 40 per cent of all fresh water use. Industry uses water to cool machinery and as a power source. Historically, the rise and fall of the many civilizations have often been linked to the quality and quantity of topsoil of the surface layer and therefore to water availability. Water feeds plants and irrigates lands, allowing farmers to produce crops. Most of the water in the hydrosphere is salty and much of the fresh water is frozen. It has been estimated that all the oceans contain 97% of the plants water, all the seven continents (lands) contain only about 2.8% and the air atmosphere about 0.x001%. About 77% of the water associated with land is found in ice caps and in big glaciers of the world and about 22% is found in groundwater, much of which is uneconomical to strive. This leaves only a small percentage of readily manageable fresh water as a resource of the water supply.

Crop plants take up water from the soil system to maintain cell turgidity and fix CO2 from the atmosphere to provide, for example: food, fuel, fiber, drugs and forest products, to mankind and animals. Plants transpire 100-300 times more water during the assimilation of CO2 than is required for their growth and production of yield. It has been estimated that 600 kg water is transpired to produce 1 kg of dry maize, and to produce 1 kg dry biomass, 225 kg of water is transpired. It was further reported that to produce 1 kg of sucrose, sugarbeet plants transpire 465 kg of water and to produce 1 kg dried biomass, they transpire 230 kg of water. A shortage of fresh water is probably going to be the most serious resource problem of the world will face after a few years from now. Three quarters of the fresh water on the planet are held in the polar icecaps and big glaciers and thus not available use.

In this world, the most water-rich country is iceland with more than 5 x 105 cubic meters per person per year, whereas the most water-poor is Egypt, with just 0.02 cubic meter. Some 70 per cent of the water people use, goes to irrigation. Since 1950, the amount of irrigated land has tripled and one-third of the world's food is grown on it. The most serious long-term problem is salination (salinity). When irrigation water soaks down into the soil, it absorbs mineral salts from the earth, flushing them to the surface. As the water evaporates, these salts dry out on the field, gradually destroying their fertility. Some 25 per cent of Pakistan's cultivated land have been damaged in this way, because 80 per cent of the agricultural lands cultivated through irrigation.

Water is a key input for agriculture and is made available to farmers through irrigation network. The design cropping intensity for Pakistan's irrigation system was about 60-70%, but now the cropping intensity is more than 120%. This much higher water requirement demands an efficient canal irrigation system. Such a canal irrigation system can only be managed with proper operation and maintenance (O and M). In Pakistan, the task of irrigation system operation and management is in the hand of provincial irrigation departments. The government is spending heavily on the operation and maintenance of the irrigation system every year, but a shortage of fund is still the major problem. This situation has resulted in the deterioration of the canal irrigation system.

The water shortage is the most serious crisis facing the country to day. The Indus river system is its lifetime. But its canal command system is drying out of water. The shortage of water is afflicting all the provinces of Pakistan. Pakistan's irrigation system has three major water storage reserves, 19 barrages and headworks, 132 links/canals and 43 canal commands covering about 90,000 chaks/villages/goths and stretching over 40,000 miles. Available figures regarding existing water resources indicate that the quantum of water entering the rivers aggregates to about 145 million acre feet per annum. Of this, about 109 million acre feet is transferred to canals annually and the remaining 40 million acre feet flows down into the sea, because of lack of storing capacities. The volucime of water entering irrigation watercourses from canals amounts to 78 million acre feet per annum. Water obtained from 560000 public and private tubewells for irrigation purposes has been estimated at 44 millions acre feet annually. Thus, the total quantum of water entering the watercourses both from canals and tube-wells aggregates to 122 million acre feet annually. The agriculture sector was never able to make optimum advantage of the available water resources mainly due to inefficient water management. Of the 145 million acre feat water entering the canals each year, about 26 million acre feet is lost in transit due to a number of factors. Besides, about 40 million acre feet water is lost within the watercourses themselves. Hence, only 73 million acre feet water reaches the fields. About 18 million acre feet water is wasted in the fields. Taking into account all the losses only 55 MAF water is anally left for crop growth, while 90 MAF water per annum goes waste, which is estimated around 62 per cent of the total.

Three major dams Mangla, Tarbela and Chashma were constructed for the purpose of generating electricity and irrigating agricultural land. In addition, there are 23 barrages/head works/syphons; main irrigation canals are 45, which have extended up to 40,000 miles. Similarly, there are 90,000 watercourses, which are extended up to one million miles. Mangla Dam (on river Jhelum): Earth filly height 380 fit above river bed, length 10300 ft. gross storage capacity 5.85 MAF, main spill way 870,000 cusecs. Lakes are 100 square miles, hydropower generation 1000 MW capacity, completed in 1967. Tarbela Dam (on river Indus): Earth and rock fill, height 485 fit above river bed, length 9000 ft. gross storage capacity 11.3 MAF, spill way capacity 650,000 cusecs, lake area 100 square miles hydropower generation 1728 MW, completed in 1983. The dams have been constructed for the purpose of depleting capacity of the existing water reservoirs call for at least several small dams in the country to meet the water requirements. In view of the mounting gravity of the developing situation there is an urgency of initiating a timely more to expedite development of adequate water resources to meet the increasing need of the economy adequately, without any more loss of time. There is need to construct more small dams/barrages in the country at least six in the Punjab, four in Sindh, three in NWFP and two in the provinces of Balochistan. The names of some dams were appeared for construction in the papers. Such dams are Bhashah, Munda dam, Chotiyarion dam also in Thar (Ravee Canal), and some barrage (Sehwan) and canals in Balochistan, NWFP and Sindh. During the last 30 years, no any new dam was constructed, thus we are neglecting this dire requirement of water for the country and thus country is today suffering for this criminal neglect in the form of drought and acute water shortage throughout the country specially Sindh and Balochistan. Punjab province has plenty of sweet sub water and in case of shortage, it can meet its requirement by sinking more tubewells. But, Sindh has brackish sub-soil water, which cannot be used for irrigation purposes. The water shortage in Sindh province will be much more acute in the coming years and this disaster can be averted only by undertaking construction of new dams on war footing.

The country in the next 10 years, will loss water storage capacity equivalent to Mangla dam, as 5 x 105 tons of sedimentation are flowing into dam every day. According to an estimate within 10 years the country's water storage capacity would deplete by over six million acre feet (MAF), which is equal to water stored in Mangla dam and this shortage will continue to increase with every passing year and the biggest suffer will be the province of Sindh. The gigantic dams built earlier at Warsak, Mangla and Tarbela on rivers Kabul, Jhelum and the Indus, respectively, have continued emitting signals of wearing down and now they have to be supplemented with new dams to meet the needs of the times. In the meantime, the growing need of water for irrigation and other purposes has acquired alarming proportions.

Pakistan is fortunate in the soils, topography and climate, which are suitable for year round agriculture. Major agricultural areas lie within the plains formed by Indus river and its tributaries, namely Kabul, Chenab, Ravi, Jhelum and Sutlej. Indus plains are like a tunnel with number of water sources at the top, converging into single stream, which flows into the Arabian Sea, near the city of Karachi. First canal were constructed some 5 to 6 centuries ago and extended under the great Moghul emperors. In earlier 19th century, there were numerous inundation canals leading from Indus and its tributaries. World's largest contiguous irrigation project was started in 19th century. After independence in 1947, many more developments in the canal systems were made. Different barrages/canals i.e., (Kotri barrage-1956, Taunsa barrage-1958 and Guddu barrage-1962), link canals (Marala-Ravi (MR), Bambanwala-Ravi-Bedian-Dipalpur (BRBD) and Balloki-Salimanki (BS) were constructed.

Groundwater also contributes significantly to meet the country's agricultural as well as domestic needs. Pakistan is fortunate enough to have an abundant groundwater as a consequence of gravity fed irrigation network. In all, about 80 per cent of the groundwater are from marginal to haradous in quality and only 24.7 million acres are underlain by usable groundwater. Nearly 46.4 MAF of groundwater is recovered from pumping through 400,000 private and 15000 public tubewells. However, usable groundwater with salinity level of less than 1500 mg/l is only 23.4 MAF.

The third major source of fresh water is rain. Estimated average annual rainfall in the cultivated commanded areas of the Indus basin is 23 MF. In view of the fact that agriculture in rain-fed areas entirely depends on precipitation, there is pressing need to harvest more rain and conserve maximum moisture in these areas. The lowest limit for rainwater harvesting 50 to 80 mm of rainfall. In rain-fed areas of Pakistan rain-fall varies from less than 100 mm to over 1000 mm with an average of about 400 mm annually. Rainwater collects just 20 to 30 per cent of the precipitation.

Domestic waste water may be another potential source of irrigation, if collected and treated properly. It can contribute significantly to the country's limited and fast depleting water resources, improve soil fertility and alleviate the threat of water pollution and consequential health hazards. Domestic waste water is widely used as a source in many parts of the world for a variety of purposes like soil fertilization, aquatic weed production and irrigation. High cost of artificial fertilizers and presence of valuable plant nutrients in waste water justify a trade-off analysis for its use as irrigation water. It has been recommended that waste water should be used for irrigation only after secondary treatments and for irrigating fodder crops to avert any damage to human health. The population of the 10 most populous cities of Pakistan is 23 million and per capita waste water generation is 80-200 lit/day, depending upon climatic conditions and living habits. Thus, about 0.54 to 1.36 MAF of water can be developed annually if the technology of waste water treatment is introduced in those cities. This water may be used for irrigating agricultural lands in the vicinity of these cities and irrigation water apportioned for those lands may be diverted to other cultivable lands. In this way other areas of wasteland can also be brought under cultivation.

According to a report by the year 2001, Pakistan would require 78.7 MAF of irrigation water at farm gate to meet its agricultural needs against the present supply of 55.8 MAF. This is only possible when the available water resources are efficiently managed and economically utilized. There is therefore, a dire need of minimizing conveyance losses and improving field water use efficiency. Conveyance losses can be minimized by strengthening on-farm water management and command water management programmes for improving and lining of water delivery systems. The field water use efficiency can be improved by imparting training to farmers in proper management and effective utilization of irrigation water at their farms. By this, not only the precious irrigation water can be saved from going-waste but also threat of waterlogging and salinity could be lessened besides increasing crop yields. About 7.16 MAF of fresh water is lost before reaching farm gates. If only 50 per cent of this water is saved and put into use, not only future shortfall for the year 2001 can be tackled but 12.9 MAF of surplus water would also become available. Any reduction is discharge to the Arabian Sea, improvement in rain water harvesting techniques, proper treatment of domestic and industrial waste water, conjuctive use of fresh and saline water and proper on-farm water management practices would bring additional water for crop production. The development potential of this water can be 50 to 60 MAF annually. Inequitable water distribution is another problem, which Pakistan is currently facing. Farmers at the heads are getting more water than the farmers at the tails. This has resulted in gradual rise of watertable at the heads and salinization of agricultural lands at the tails of watercourses. For achieving self-sufficiency in food items it is imperative to increase water supply. The present warabandi system of water distribution, therefore, needs modification keeping in view the water requirements of existing cropping patterns and intensities.