FRESH WATER PERSPECTIVE AND AGRICULTURE
Water is one of the most fundamental of natural resources that a country must harness in its efforts for rapid economic development
By Dr. S.M. ALAM, NIA, Tando Jam.
May 20 - June 02, 2002
Water is the essence of life and a constant supply of clean, healthy water is essential for all citizens of the country. Most of the water is the hydrosphere is salty and much of the fresh water is frozen. Oceans contain 97 per cent of the planet's water, continents about 2.8 per cent and the atmosphere about 0.001 per cent. About 77 per cent of the water associated with land is found in the caps and glaciers and about 22 per cent is found in ground waters, much of which is uneconomical to retrieve. This leaves only a small percentage of readily manageable fresh water as a resource of the water supply. Water, which is a combination of oxygen and hydrogen gases, is the earth's most distinctive constituent and is an essential ingredient of all creatures living on the earth's surface. It can neither be created in a factory, mill, industry nor in a laboratory despite common universal knowledge. Its availability is one of the most limiting environmental factors affecting crop productivity and numerous human applications.
Water is a substance of paramount ecological, economic and social importance. Water is among the most essential requisites that nature provides to sustain life of plants, animals and humans. The total quantity of fresh water on earth can satisfy all the needs of human population if it is evenly distributed or accessible to all present on the earth. Water is used in a variety of ways at different levels. Fresh water, through currently abundant in most parts of the world, is likely to become increasingly scarce in coming decades for two reasons: i) Decline in the total supply of water due to greater net consumption and ii) contamination and pollution. The tremendous increase in water consumption has also resulted in massive underground pumping and this also resulted in falling of water tables on all the parts of the country. Safe drinking water is essential for good health and is a pre-requisite to the disease, most common in developing countries. One of the main objectives of management of water is to provide safe water to people in adequate quantities for drinking, food preparation and personal bathing and various other uses.
Sufficient supply of fresh water in big cities of Pakistan and particularly in Sindh is becoming chronic and alarming. There is a report on the condition of drinking water in Karachi. Today, Karachi is home to around 12 million people. Half of them live in slum townships, with little or no water through the mains. Even the 'rich' half usually have to await days before anything trickles through their pipes. And the coloured liquid that finally emerges is usually too contaminated to drink. According to state-owned Karachi water and sewerage board the city needs more than 2500 million litres of water each day. The Water Board currently supplies 1650 million litres of which nearly 40 per cent is lost from leaks and theft. The global average for replacement of water in streams is 18 to 20 years, while water in the atmosphere is replaced every 12 days. Deep groundwater requires several hundred years or more for renewal, except for deep fossil aquifers, which are non-renewable on a human time scale. This natural recycling and purification process works and provides plenty of fresh water as long as we don't pollute the water faster than it is replenished, overload it with slowly degradable and non degradable wastes, or withdraw it from slowly renewable underground supplies faster than it is replenished. Unfortunately, we are disrupting the water cycle by doing all of those things. Earth's usable fresh water is very unevenly distributed around the world. Because of differences in average annual precipitation, the world is divided into water "haves" in tropical and temperate climate zones and water "have-nots" in arid and semiarid climate zones.
It has been assumed that by 2025 the volume of water needed to produce food is expected to have increased by at least 50 %, because of population growth and the demand for higher living standards. Growing water shortages threatens to reduce the global food supply by more than 10 per cent. Agriculture already accounts for about 70 % of water consumption worldwide and UN projects the amount of water used in irrigation may double by 2025. This situation is worsened by pollution, which results in decreased water availability for human use. Industrial, domestic and agricultural pollution continuous to severely degraded water quality in many rivers, lakes and groundwater resources. Excessive use of water by many industries is also a grave matter of concern. For instance, the manufacture of compute wafers, used in the production of computer chips, used up to 18 million litres of water per day. Globally, the industry uses 1.5 trillion litres of water and produces 300 billion litres of waste water every year.
Water is one of the important substances for our existence and as such its occurrence and distribution in land, its physical and chemical properties and interaction with the environment are of vital importance. Water provides important habitats for wild plants and animals. We use water in agriculture and industry, for leisure activities and of course for drinking. The uses of water are numerous and life without water is impossible. A man can live without food for longer than he can live without water or air. Water is the earth's most prominent constituent and is an essential ingredient of all life. The criteria fixed by WHO for drinking water is 500 mg for salts per litre of water. Water feed plants and irrigates lands, allowing farmers to produce varieties of crops in the fields. Without the use of water crop productivity is impossible. Application of fertilizer input to the farm lands without irrigation water is purposeless and meaningless. The water we use eventually returns to watercourses. Even the water that evaporates will ultimately return to earth as rain water.
Pakistan is a water-short, land-rich and demographically burdened country, where the population is increasing at a rapid rate. At present, the population growth of the country is flourishing at a rate of 8 births per minute, 480 births per hour, 11,520 per day and 4,204,800 per year and so on. In this way, the per capita availability of water has been constantly decreasing for the last fifty four years. According to the internationally recognized water scarcity indicators, the present level of water shortage in Pakistan hampers the growth and well-being of its people, and severe constraints may be caused to human life, if this downward trend continues. It is tragic to note that downward trend is continuing and two popular Tarbela and Mangla dams have lost about 25 per cent and 20 per cent of water storage capacity because of salination. For Pakistan, water is the critical commodity for agricultural production due to arid and semi-arid conditions.
Water is a key input for agriculture and is made available to farmers through irrigation network. The designed 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. 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. There has been an acute and persistent shortage of irrigation water from river Indus and its canal in Guddu and Sukkur Barrage commandment areas posing major threat to exist Kharif crop. It must be mentioned here that sowing of cotton, sugarcane and rice crops will possibly be delayed because of insufficient water supply. Officials in Sukkur and Guddu Barrages enforced Warah Bundi of water with tailenders suffering the most. Sukkur Barrage completed in early 1930s was designed to irrigate at least 320,000 acres of farmland in upper and lower Sindh. This barrage has total seven canals on both sides, one of its canals, Nara is the largest in the world. Presently, some 2 x 104 - 2.5 x 104 cusecs (cubic feet per second, a unit to measure running water) water is being discharged from Guddu and Sukkur barrages. The amount of water is insufficient for the present day agriculture requirement. In the absence of regular yearly desalting, the water problem has aggravated further. Had there been regular extensive desalting, the water flow situation would have been better, even with less seasonal supply. About 50 % of total delivered water from our integrated irrigation system is lost by seepage from earthen channels, water courses and by deep percolation due to filed application. This has caused a serious disturbance in the hydrological environmental balances in the irrigated areas in Pakistan.
Pakistan, an agricultural country at birth, inherited with a monsoonal based economy. The country's economy depends largely on the vagaries of weather and the changing moods of rainfall, where in the north, it is high, while in the south, it is in decreasing order. It is an established fact that crop harvests of a farmland increase, if water supply is timely and adequate. Ultimately, a low rainfall causes a substantial short fall in harvests. South Asia has witnessed the changing global weather phenomenon over the last many years. It is reported that a few years back, Bangladesh and eastern part of India were lashed by heavy monsoon rains, but the rainfall in the western region of Pakistan and India were below the normal. The drought in some part of Sindh and Balochistan in Pakistan and in Rajasthan and Gujrat in India were a wake-up call for these countries. The winter rains during 2000- 2001 were an excessively delayed with the result that the usually wet period of January and February was of (almost) the depletion of water from the once mighty Indus river, which in fact has robbed the region of its historical importance and prosperity. The area, which once boasted of being the granary of the Indus valley, supplying culinary waves to towns and cities gradually glided with a barren land, unable to feed its own people including fishermen living on boats in the river.
The water shortage is the most serious crisis facing the country today. The Indus river system is its lifetime. But its canal command system is drying out of water. The mighty Indus presents a deserted look. Now, the cattle and animals are grazing and moving in the dried river beds of mighty Indus. The shortage of water is afflicting all the provinces of Pakistan.
The agriculture sector, which is the major user of water sets consumption will continue to dominate water requirements. The Indus river system is the prime source of Pakistan's water resources. It commands over 14 mha area and encompasses the Indus river and its major tributaries, three storage reservoirs normally Tarbella and Chashma on River Indus and Mangla on River Kabul and Jehlum, 23 barrages or head works, 12 inter river link canals, 43 independent irrigation canal commands and over, 107,000 water courses, which are complemented with a surface drainage system comparable in size. The length of the canals is about 61,000 km with command watercourses, farm channels, and field ditches covering another 1,600,000 km throughout the country. In the Indus basin irrigation system, river water is directed and by barrages and head-works into main canals and subsequently into branch canals, distributaries and minors. The flow to the farm is delivered by the watercourses, which are supplied through outlets (moghas) from the distributaries and minors. The outlet is designed to allow a constant discharge of water that self adjusts the variation in the minors.
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 move to expedite development of adequate water resources to meet the increasing need of the economy adequately, without any more loss of time. According to expert opinion, situation demands that small dams are to be developed at strategic location with four provinces, so that rainwater can be used in the rainy days. In order to check/stop the waste of precious water in water irrigation channels and watercourses have to be put to desalting process on regular basis at least once a year.
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 36 million acre feet flows down into the sea, because of lack of storing capacities. The volume of water entering irrigation watercourses from canals amounts to 78 million-acre feet per annum. Water obtained from about 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 feet water entering the canals each year, about 28 million-acre feet is lost in transit due to a number of factors. Besides, about 36 million-acre feet water is lost within the watercourses themselves. Hence, only 71 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 51 MAF water is actually left for crop growth, while 98 MAF water per annum goes waste, which is estimated around 62 per cent of the total.
The term irrigation is defined in the simple dictionary as "wetting". Soils are wetted naturally by rainfall, floods, localized surface run-off waters or from underground water table. Crop production under semi-arid, arid and sub-humid climates necessitates application of water to growing crops whether seasonally or perennially. The main purposes of irrigation are: i) to supply or replenish the root zone of growing plants with moisture, which is the basis for life; ii) to dissolve plant nutrient element in the soil and transfer it within the immediate plant roots for absorption and inside the plant itself for different growing organs and iii) to dissolve excess salts and leach it away from the soil profile to the drains. With progress in maximizing crop production in arid and semi-arid areas under irrigation, civil engineers began to improve on applying their knowledge of soil-water- plant relationships for optimum use of unit irrigation water for the production of maximum economic crop yield per unit land irrigated.
The present agriculture production in the country is supported by an irrigation network that is the largest integrated irrigation system in the world. The waters of the Indus River and its tributaries feed the system. Water is a unique natural resource. In Pakistan, conservation and management of water supplies is crucial as the demand for water continues to rise because of its uses by burgeoning population. Pakistan agriculture is predominantly irrigated. The present day canal irrigation network in the country, developed over a period of one and a half century, is considered to be one of the largest contiguous irrigation systems in the world. Irrigation is the life blood of its agriculture, and irrigation plays a central role in Pakistan's economy. Irrigated land supplies more than 90 % of agricultural production and most of the country's food, which accounts for 25 % of GDP and 54 % of employed labour force and substantial foreign exchange earnings.
Within the water courses command (an area ranging from 80 to 285 hectares), farmers receive water, proportional to their land holdings. The entire discharge is given to one farm for a specified period on a several day rotation. The rotation schedule, called Warabandi is established by provincial irrigation department, if the farmers can not reach mutual agreement. Pakistan has significant, water resources, but these are inadequate to some extent for crop production on the available lands. The river flows are highly seasonal. Roughly, 85 % of annual flows are in Kharif season (summer) and only 15 % in the Rabi (winter), but Pakistan does not have enough reservoir capacity in its irrigation system to store seasonal waters. Moreover, due to inadequate water availability in winter and at the beginning and end of summer, cropping intensity is remained exceptionally low. The physical capacity of the irrigation canal system is also remain constant during periods of high demand for crop water. In some areas, where underground fresh water is available, surface supplies can be supplemented by tubewells, but opportunities for further exploitation of groundwater are limited.
The greatest asset the country possesses is the mighty river Indus with its tributaries and the vast network of canals, channels, and water courses commanding nearly 34.5 (20.51 million hectares) millions acres of culturable area. Annual net addition to salts is of the order of 1.3 tons per acre in southern region of the country and 0.4 tons in the northern and the average annual addition of salts to the Indus is as high as 16 million tons. According to the available and irrigation demands of the country, the total requirement of water was estimated at 260 million acre feet, while the Indus system had only 140 MAF available annually, out of which currently 110 MAF was being diverted into the huge canal system.
Agriculture is the most important economic activity. It is the barometer of the health of the national economy. In order to get maximum production of crops from the fields, it is essential to have an effective and efficient drainage system to sustain environmentally sound irrigated agriculture. The acquifer on which the Indus Basin Irrigation System is overlaid average 3,000 feet deep and is completely unified. Waterlogging and salinity are the principal threats to the sustainability of irrigated agriculture in Pakistan, 37.6 per cent of the gross command area is waterlogged of which 15 per cent is severely waterlogged, 14 per cent of the surface is saline of which 6 per cent is severely saline. The water table in the Indus plain was deeper than 90 feet in the century. By 1961, it was shallower than 10 feet in 38 per cent of the area, by 1981, it was shallow than 10 feet in 45 per cent of the area, and by 1989 it was shallower than 5 feet in 15 per cent of the area. While, the water table is declining rapidly in most fresh groundwater areas, it is increasing in some saline groundwater areas. The rise of groundwater table to near the surface in saline ground water areas and the consequent soil salinization are serious environmental problems associated with irrigation in the Indus Basin.
Pakistan agriculture is facing problems of soil salinity affecting the crop yields badly upsetting the water and nutritional balance of the plant due to deterioration of physical and chemical properties of soil. The impact of salinity on agriculture productivity is severe, a 25 per cent reduction in the production of Pakistan's major crops is attributed by many experts to soil salinity alone. In Sindh Province, where the problem is very severe and it is estimated that the impact may be closer to 40-60 per cent in saline ground water areas. The critical threshold at which salinity begins to affect the productivity of agricultural lands varies by crops. Similarly, the impacts of waterlogging on yields are startling. High groundwater tables inhibit root growth and therefore reduce crop yields. the principal causes of waterlogging and salinity are irrigation to the crops, without drainage, over irrigation, and low delivery efficiency of the irrigation water 35 to 40 per cent from canal head to root zone and drainage system.
The semi-arid climatic condition prevailing in Pakistan also leads to substantial accumulation of salts in the root zone. Groundwater pumping, which is unregulated further, aggravates the situation by mobilizing salts dissolved in the groundwater acquifer, if the efficient can not be safely disposed off. In order to augment the agricultural production in the country, there is an ever greater need to streamline the strategy to bring reforms in the irrigation and drainage sector, and address the critical issue of waterlogging and salinity. Agriculture has a central role in alleviating concentration of the poor in rural areas. It is the main engine of growth for the economy of the country. Pakistan agriculture depends heavily on irrigation, which covers 79 per cent of the total cropped area of 20.8 million hectares (51 million acres). Irrigated agriculture in turn is by far the dominant user of available water supply, accounting for 98 per cent of direct flows and bulk of re-flows. In order to further improve the drainage system for irrigation, there is urgent need for planning, regulation, construction, financing, management, operation and maintenance of the drainage system to meet the new challenges of the farmers of the country.
The world's fixed supply of water in all forms (vapor, liquid, and solid) is enormous. If this water were spread evenly over Earth's surface in liquid form, it would form a layer nearly 3,000 meters (9800 feet) deep. However, only a tiny fraction of the planet's supply is available to us as fresh water, and that is distributed very unevenly. About 97% of Earth's volume of water is found in the oceans and is too salty for drinking, growing crops, and most industrial uses except cooling. Of the remaining 3% is fresh water, about 2.997% of this is locked up as ice at the poles and in glaciers or its groundwater that is too deep and too expensive for us to extract. This means that only about 0.003 of Earth's total volume of water is easily available to us in lakes, soil moisture, exploitable ground water, atmospheric water vapor, and streams. If the world's water supply were only 100 liters (26 gallons), our usable supply of fresh water would be only about 0.003 liter (one-half teaspoon). Fortunately, this supply of fresh water is continually collected, purified, and distributed in the hydrologic cycle. As population and industrialization increase, water supply crises in already-water-short-regions will intensify. Unpredictable changes in rainfall patterns brought about by a possible enhanced greenhouse effect are likely to cause great disruption in these and other areas. It's hard to predict where such shifts in annual precipitation will occur, but one study suggests that most of the entire western United States — much of which is already short of water — could experience a 40% to 76% drop in levels of precipitation.
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 province of Balochistan. The government has decided to construct Gomal Dam in NWFP, Hingol and Mirani dams in Balochistan, Thal reservoir in Punjab, Kachhi and Ranni canals in Sindh. These small dams would cost Rs. 20 to Rs. 25 billion each and would have the capacity of storing 1.0 to 1.5 MAF of water. These would bring 200,000 to 300,000 acres of barren land under cultivation. Kachhi canal would alone bring 500,000 acres of barren land under cultivation in Balochistan, which would help boost country's cotton export by 4 to 5 million dollars. Apart from these small dams, the government has approved installation of 10,000 tubewells in all the four provinces. Out of these 10,000 tubewells, 5,000 would be installed in Punjab, 3,000 in Sindh and 1,000 each in NWFP and Balochistan. Agriculture sector was an important segment of the economic revival plan, it constituted 25.6 per cent of the GDP and contributing over 70 per cent of country's foreign exchange earnings through the export of raw, semi-processed and processed products like cotton. Half of the country's work force was employed in the agriculture sector. Wheat production increased to 21.1 million tons and cotton output reached 11 million bales, while rice production attained the level of 5.2 million tons in the year 1999-2000. The names of some dams were appeared for construction in the newspapers. 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 especially in Sindh and Balochistan. Punjab province has plenty of sweet sub-soil water and in case of shortage, it can meet its requirement by sinking more tubewells. But, Sindh has mostly 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.
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 hazardous 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/1 is only 23.4 MAF. For practical use, the groundwater is classified into three classes viz, usable, marginal and hazardous. Usable quality waters are fresh (EC less than 1.5 dS/m) and can be used directly for agriculture. Marginal quality waters (EC 1.5 to 3 dS/m) cannot be used directly because of higher concentration of salts and have to be diluted with sweet waters for agriculture. In the Indus plains, the sweet water zone (usable) covers 33 % of the area, while 13 % is moderately saline (marginal) and 54 % is highly saline (hazardous). By contrast, current FAO guidelines for water quality for agriculture set the upper limit for unrestricted use at an EC value of 0.7 dS/m.
The third major source of fresh water is rain. Estimated average annual rainfall in the cultivated commanded areas of the Indus basin in 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 is 50 to 80 mm of rainfall. In rain- fed areas of Pakistan, rainfall varies from less than 100 mm to over 1000 mm with an average of about 400-mm annually. In the year 2001, there was acute shortage of rainfall and this fact reduces the inflow of rivers. Domestic wastewater 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 wastewater justify a trade-off analysis for its use as irrigation water. It has been recommended that wastewater should be used in the country for irrigation only after secondary treatments and for irrigating fodder crops to avert any damage to human health.
Water is one of the most fundamental of natural resources that a country must harness in its efforts for rapid economic development. The role of water in the development process cannot be over emphasized. The demand for water in the country has increased tremendously over the years and will continue to increase in view of the accelerating pace of population growth, urbanization and industrialization. Water resource development should be the cornerstone of national development in the country.