GLOBAL WATER CRISIS AND PAKISTAN
The world's thirst for water is likely to become one of the most pressing resource issues of the 21st Century
By Dr. S M. Alam NIA, Tando Jam
Mar 25 - 31, 2002
Water is the earth's most distinctive constituent, natural resource and is essential ingredient, and premium of life. It is among the most essential requisites that nature provides to sustain life of plants, animals and humans. The uses of water are numerous and life without water is impossible. A constant supply of clean and healthy water is most essential for all citizens of the country. Water is of the human body's primary and basic need. It is a well documented fact that the universe is composed of 29 % land and 71 % of water (both sweet and fresh) (Massoud, 1981). However, a shortage of fresh water is probably going to be most serious resource problem, the burgeoning population anywhere of the planet (earth) will face, in the next coming years. As with human food, this problem is not one of global shortage, but one of uneven distribution. Water associated with land and is held in the polar icecaps and big glaciers of the world and about 22 % is found in groundwater and much uneconomical of which is for use. This scenario leaves only a small per centage of readily manageable fresh water as a source of the water supply, where water is plentiful, people are frequently a few and vice-versa. The country Iceland in Europe is the most water-rich country with more than 500,000 cubic meters per person per year; but most water poor country is Egypt in Africa, with just only 0.02 cubic meters per person (McRae, 1994). Most of the water in the hydrosphere is salty and much of the fresh water is frozen. It has been estimated that vast oceans all over the world contain about 97 % of the planet's water seven continents contain about 2.8 % and the atmosphere about 0.001 %.
The world's thirst for water is likely to become one of the most pressing resource issues of the 21st Century. Global water consumption rose six-folds between 1900 and 1995 more than double the rate of population growth and continues to grow rapidly as agricultural, industrial, and domestic demand increases. Globally, water supplies are abundant, but they are unevenly distributed among and within countries. In some areas, water withdrawals are so high, relative to supply, that surface water supplies are literally shrinking and groundwater reserves are being depleted faster than they can be replenished by precipitation. This situation has already caused serious water shortages to develop in some regions, short changing human water needs and damaging aquatic ecosystems. A 1997 United Nations assessment of freshwater resources found that one third of the world's population lives in countries experiencing moderate to high water stress. To arrive at its estimate, the United Nations determined each country's ratio of water consumption to water availability its use-to-resource index which is a good gauge of overall pressure on water resources. Moderate to high stress translates to consumption levels that exceed 20 per cent of available supply (Todd, 1970).
The U.N. assessment makes clear that the global water situation will get considerably worse over the next 30 years without major improvements in the way water is allocated and used. In fact, the United Nations projects that the share of the world's population in countries undergoing moderate or high water stress could rise to two thirds by 2025. Population growth and socio-economic development are currently driving a rapid increase in water demand, especially from the industrial and household sectors. Industrial water use, for example, is predicted to double by 2025 if current growth trends persist. Water use in agriculture is slated to increase as world food demand rises. Agriculture already accounts for about 70 per cent of water consumption worldwide, and the United Nations projects a 50 to 100-per cent increase in irrigation water by 2025. Much of the projected increase in water demand will occur in developing countries, where population growth and industrial and agricultural expansion will be greatest. However, per capita consumption continues to rise in the industrialized world as well.
Water pollution adds enormously to existing problems of local and regional water scarcity by removing large volumes of water from the available supply. Water quality in most of the developed countries has steadily improved in recent years, thanks to strict legislation and major investments in new water and sanitation infrastructure. Even in the developed world, however, wastewater is not necessarily treated before discharge. In the southern member states of the European Union, about 50 per cent of the population is not yet connected to sewage treatment operations. The situation is far worse in many developing countries. Water scarcity has been exacerbated and human health gravely damaged by accelerating contamination of usable water supplies, especially in rapidly urbanizing areas.
Many developing countries undergoing rapid industrialization are now faced with the full range of modern toxic pollution problems eutrophication, heavy metals, acidification, persistent organic pollutants (POPs) while still struggling to deal with traditional problems of poor water supply and lack of sanitation services. The pollution threat is particularly serious when it affects groundwater supplies, where contamination is slow to dilute and purification measures are costly. Ground-water reserves are estimated to provide more than 50 per cent of domestic supplies in most Asian countries; yet, these countries are currently experiencing rapid growth in the mining and manufacturing sectors two big sources of groundwater contamination.
As clean water supplies have diminished, competition for them has been growing, usually between expanding urban areas and rural users. Where systems of water law and allocation exist, water markets can operate to transfer supplies between buyers and sellers for an agreed price. Such systems are operating with some success in an increasing number of countries, including the western United States and Australia. However, effective water pricing, which sets water prices high enough to discourage waste, remains a highly sensitive issue in low-income countries, where most people depend on irrigated agriculture for their living. Even so, socio-economic development in water-scarce countries may depend critically on more regional distribution of scarce supplies. Planners in China have estimated that a given amount of water used in industry generates more than 60 times the value of the same water used in agriculture. Better management of water resources is the key to mitigating water scarcities in the future and avoiding further damage to aquatic ecosystems. In the short term, more efficient use of water could dramatically expand available resources. In developing countries, for example, 60 to 75 per cent of irrigation water never reaches the crop and is lost to evaporation or runoff. Although the use of water-efficient drip irrigation has increased 28-fold since the mid-1970s, it is still employed in less than 1 per cent of the world's irrigated areas.
In the longer term, however, the U.N. water assessment makes clear that looming water crises in many regions must be addressed through hard policy decisions that reallocate water to the most economically and socially beneficial uses. Far greater emphasis on water-efficient technologies and pollution control is also essential. However, even with measures to contain the growth of demand and use water more efficiently, new supplies will be needed. The World Bank has estimated that the financial and environmental costs of tapping new supplies will be, on average, two or three times those of existing investments, because most of the low-cost, accessible water reserves have already been exploited. The U.N. study also highlights the potentially desperate situation of developing countries that combine high water stress with low per capita income. The majority of these countries are found in the arid or semi-arid regions of Africa and Asia. Many use most of their available water supplies for farm irrigation and suffer from a lack of pollution controls. Future development in these countries appears severely constrained because they have neither the extra water nor the financial resources to shift development away from intensive irrigation and into other sectors that would create employment and generate income to import food (Hanks, 1983).
The challenge for future water management is enormous. In 1995, 29 countries with populations totaling 436 million experienced water stress or scarcity. By 2025 about 48 countries will do so and the number of people adversely affected will exceed 1.4 billion, the majority in the least developed countries. An estimated 3 billion people will be living in water-stressed countries in 2035. In addition, many countries with limited water availability also depend on shared water, which increases the risk of friction and social tensions as is already the case along the rivers Euphrates, Jordan, and the Nile. Improved water management has brought enormous benefits to people in developing countries. Between 1950 and the mid-1980s global per capita grain production increased by 38 per cent and grain prices dropped by about 50 per cent. The driving force behind this has been an increase in irrigated area (from 100 to 250 million hectares) and an increase in productivity. Over the past 20 years more than 2.4 billion people have gained access to water supply and 600 million to sanitation, and about 20 per cent of the world's electricity comes from hydro-electric dams.
Since the mid-1980s there has been a pronounced slowing down in food production from irrigated agriculture, both as a result of little expansion in irrigated area, and reductions in productivity growth. There are still about 1 billion people without an adequate supply of drinking water, and about 2 billion people without adequate sanitation services. Groundwater aquifers are being pumped unsustainably in many developing and some developed countries. Ten per cent of food is grown with water pumped from over-exploited aquifers. And much aquatic biodiversity is being lost in overstressed rivers the rate of extinction of freshwater fish species is five times that of saltwater species. Spreading water shortages threaten to reduce the global food supply by more than 10 per cent. Left unaddressed, these shortages could lead to hunger, civil unrest, and even wars over water, reports a new book from the Worldwatch Institute (Anon, 1998; 1999).
Irrigation accounts for two thirds of global water use, but less than half that water reaches the roots of plants. Without increasing water productivity in irrigation, major food producing regions will not have enough water to sustain crop production. Some 40 per cent of the world's food comes from irrigated cropland. But the productivity of irrigation is in jeopardy from the over pumping of groundwater, the growing diversion of irrigation water to cities, and the buildup of salts in the soil. Our civilization is not the first to be faced with the challenge of sustaining its irrigation base. A key lesson from history is that most irrigation-based civilizations fail.
Today, irrigation problems are widespread in the grain-growing regions of central and northern China, northwest and southern India, parts of Pakistan, much of the western United States, North Africa, the Middle East, and the Arabian Peninsula. Water tables are dropping steadily in several major food producing regions as groundwater is pumped faster than nature replenishes it. The world's farmers are racking up an annual water deficit of some 160 billion cubic meters-the amount used to produce nearly 10 per cent of the world's grain. The over pumping of groundwater cannot continue indefinitely. Eventually the wells run dry, or it becomes too expensive to pump from greater depths. Meanwhile, the amount of irrigated land per person is shrinking. It has dropped 5 per cent since its peak in 1978, and will continue to fall. At the same time, one in five hectares of irrigated land is damaged by salt the silent scourge that played a role in the decline of ancient Mesopotamian societies and other ancient civilizations.
So much water is being diverted for irrigation and other human uses that many major rivers now run dry for large portions of the year including the Yellow in China, the Indus in Pakistan, the Ganges in South Asia, and the Colorado in the American Southwest. The Yellow River, the cradle of Chinese civilization, ran dry for a record period in 1997, failing to reach the sea for 226 days. With population growing rapidly in many of the most water-short regions, water problems are bound to worsen. The number of people living in water-stressed countries is projected to climb from 470 million to 3 billion by 2025, the study notes. Already many countries do not have enough water to meet domestic demands for food, creating a source of potential political instability. Water-short countries are increasingly turning to the world grain market. In the swathe of countries from Morocco across North Africa and the Middle East to Iran, virtually every nation is facing water shortages as rising populations draw against a limited supply and as irrigation water is diverted to satisfy growing urban demand. To meet their food needs, these countries are importing grain. (Importing a ton of wheat is the equivalent of importing 1,000 tons of water.)
Last year, the water required to produce the grain and other farm products imported into the region was equal to the annual flow of the Nile River. And this deficit is growing year after year. Jordan is importing some 91 per cent of its grain, Israel 87 per cent, Libya 85 per cent, Saudi Arabia 50 per cent, and Egypt 40 per cent. As water shortages continue to mount, it is dangerous to presume, as many officials do, that there will be enough exportable grain to meet the import needs of all water-short countries at a price they can afford. Most of the growth in water-stressed populations will be in South Asia and sub-Saharan Africa, where the majority of the world's poor and malnourished are today. In five of the world's hot spots of water dispute the Aral Sea region, the Ganges, the Jordan, the Nile, and the Tigris Euphrates the population of the nations within each basin is projected to climb between 44 and 75 per cent by 2025. Some 260 rivers flow through two or more countries, but in most cases there is no treaty among all the parties that sets out how that river water should be shared. In the absence of water-sharing agreements, tensions are bound to rise.
Irrigation's heavy water demands are also damaging the health of the aquatic environment-shrinking wetlands, reducing fish populations, and pushing species toward extinction. Using water as inefficiently as we do today, meeting the food demands of the projected 8 billion people in 2030 would result in costly losses of ecological services that the economy depends upon. To meet the challenges of a water- short world, there is a need to obtain a Blue Revolution to dramatically boost water productivity. Most farmers today irrigate the way their predecessors did hundreds of years ago. Just as raising land productivity helped meet food needs during the last half of this century, boosting water productivity will be the agricultural frontier during the next century. The challenge today is to substitute technology and better management for water. A possible idea to diverse and creative mix of "Blue Revolution" strategies are: Farmers in Pakistan, India, Israel, Jordan, Spain and the United States have shown that drip irrigation systems that deliver water directly to crop roots can cut water use by 30 to 70 per cent and raise crop yields by 20 to 90 per cent.
In the Texas High Plains, farmers using highly efficient sprinklers raised their water efficiency to more than 90 per cent, while simultaneously increasing corn yields by 10 per cent and cotton yields by 15 per cent. Rice farmers in an area of Malaysia saw a 45 per cent increase in their water productivity through a combination of better scheduling their irrigations, shoring up canals, and sowing seeds directly in the field rather than transplanting seedlings. Farmers in California's Imperial Valley are lining canals, recycling farm runoff and selling the saved water to southern California cities. Israel is now reusing 65 per cent of its domestic wastewater for crop production, freeing up additional freshwater for households and industries. Special effort is needed to lift the water productivity of millions of very poor farmers who cannot afford some of the more advanced technological solutions. Helping small-scale farm families raise their incomes and improve their food security can be a powerful engine of economic growth in the world's poorest regions. In Bangladesh, farmers have purchased 1.2 million treadle pumps, a human-powered device that allows users to pump previously inaccessible groundwater. These pumps, which to an affluent Westerner look remarkably like a Stair master exercise machine, cost $35, but typically return more than $100 in the first year of operation. In Kenya, Chad, Zambia and India, farmers are combining indigenous water-management techniques with inexpensive new technologies like low-cost sprinklers, bucket-drip systems, small-scale pumps, and check dams.
Irrigation means artificially watering the soil to initiate or increase the growth of crops. Crop water used is expressed in acre-inches,. when an acre inch is the amount of water required to cover one acre of land with one inch of water. Irrigation accounts for most of the water used throughout the world. Egypt is irrigated, about half in China, Japan and Pakistan, about 33 million acres in the United States and large parts of Europe. No country, in fact, is without its irrigation projects. Yet only one small per centage of the agricultural land is irrigated, about 400 million acres often using only a small proportion of the available water. One reason for this is that irrigation requires enormous quantities of water. For instance, one ton of sugar beets need 1000 tons of water during period of its growth; wheat 1500 tons and rice 4000 tons. Furthermore, most of the water used for irrigation cannot be re-used. At least half of its is lost by evapotranspiration. The rest is incorporated into the plants themselves (which are over 60 per cent water) and drains down into the subsoil.
By far the greatest area of irrigated land exists in hot, humid climates. Here the commonest crop is rice, which provides the main caloric intake for about one-third of the world's population. Most rice is grown in paddy fields that are flooded with about six inches of water during the growing season. There is usually no shortage of water in humid climates, either because the annual rainfall is very high, or because there are large rivers with a reliable water flow. In arid lands, on the other hand, the main problem of irrigating large area is a shortage of water. Agriculture in arid lands is also beset by problems that do not occur in humid regions. Where, there is bad drainage in flat plains, irrigation may eventually raise the water table so that the land becomes waterlogged. Goo drainage is just as important as irrigation. In the past, many peoples have neglected this principle, and many millions of acre now lie unused. Water logging prevents oxygen from reaching plant roots, which then suffocate, because of oxygen deficiency and build up of salt in soil profile. Also, waterlogged soil does not encourage crops to develop deep roots, so that during drought they are unable to tap the deeper moist soil. The Indus Basin has a flat topography, poor natural drainage and a semi-arid climate with high evaporation. In such an environment, irrigation without adequate drainage has inevitably resulted in the twin problem of water logging and salinity. Increases in diversion of river flows and seepage from canals, watercourses and irrigated areas have led to a gradual rise in groundwater levels. Within 100 years, the water-table has risen from 40 to 3 meters on about 42 % of Indus Basin. The situation is worst in Sindh province where water table is within 3 meters on 60 % of irrigated area.
Water is a unique natural resource. In Pakistan, conservation and management of water supplies is crucial as the need for water continues to rise because of burgeoning population, while its supply is limited. With this scenario, a time is approaching fast, when the only additional natural water supplies available in the country would be those salvaged from losses through consumptive waste, inefficient application and conveyance practices and run off. To overcome this crucial situation, it is imperative to save water, make its use more effective and obtain optimum results through reduction in its losses. This method will alone have a chance to guarantee adequate supplies of water for the next time to come.
Pakistan lies in the area of subtropical arid and semi-arid, where dry climate exists throughout Indus plain except northern mountainous area with temperate. Annual rainfall over much of the Indus plain is erratic and uneven and not more than 150 mm. The culturable area is about 23.25 mha, whereas 11.78 mha area is under forage and forests. This makes 35.03 mha are suitable for agriculture and forestry. The rest of area (44.63 mha) is not suitable for agriculture and forestry. Pakistan covers about 79.61 mha land area. The cultivated area is 21 mha of which 16.2 mha (77 %) area is irrigated. Water is necessary for plant growth and it serves many important functions in the growth and development of plants. The annual availability of canal water supplies can meet only little portion of the total water requirements, which put major constraints on potential crop production. The ongoing water shortage has jolted the very foundations of the national economy on the one hand and has eroded faith in the decision-making capacity of our institutions on the other. Pakistan's economy being an agricultural area has sustained an irremediable damage as a ramification of the water shortage.
The shortage of irrigation water may develop through a high degree of water losses, which are observed due to seepage in canals, watercourses and field channels and further aggravated by field application losses. The poorly managed farm irrigation application is one of the root cause of water losses. In this way a colossal amount of more than 40 % of total available water is lost, and for our existing irrigation system this is a huge loss. Unlined or poorly lined water conveyance channels cause inadequate water supply to the crops thus reducing the crop yield. Water scarcity also reduces the cultivable area thus limiting the quantum of agricultural produce. Pakistan is a land rich area (79.61 million hectares), water-short and population burdened rich country, where the population is increasing (birth of 8 children per minute) at a rapid rate and where per capita availability of water has been constantly decreasing for the last fifty three years. The present level of water shortages in the country hampers the growth and well being of its people and severe constraints may be caused to human life if such situations continue in the country.
Pakistan is basically an agricultural country and irrigation is the lifeblood of its agriculture. Of course, the land, water vegetation and human beings are important for agriculture but the development of water resources is more complex and cost intensive as compared to land and vegetation sources. For agriculture, water seems to be the major source of development. Whatever may be the nature of technology, crop production cannot be increased without recourse to adequate water resources so essential for crop growth. The recent development in agriculture land reforms, green revolution etc. was limited in scope and ineffective as regards overall development. If due emphasis is placed on irrigation development (mainly conservation of rainfall water and proper application of irrigation water, rural development could be brought about speedily than under any other measure.
God has gifted Pakistan with abundant water resources, with water flowing down the Himalayas and Karakoram heights from the world's largest glaciers, a free and unique bounty of nature for this land of alluvial plains. As a result of this natural resource, today we have the world's marvellous and the largest contiguous irrigation system that currently irrigates over 36 million hectares of land, out of 34 million hectares of cultivable lands available. 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 50 % of the employed labour force. It is also the source of raw materials for major domestic industries, particularly the cotton products, which accounts for 80 % of the value of exports. Agriculture sector is the major uses of water and its consumption will continue to dominate water requirements.
At the time of independence, we had about 67 MAF water available for diversion, this amount increased to about 85 MAF by 1960. The recent statistical data shows that the river Indus and its tributaries provide about 147 MAF during flood season, out of which nearly 106 MAF is diverted into canals and is available for irrigating 14.6 million hectares of land, while about 39 MAF of water, out flows into sea annually, whereas, over 8.6 MAF is considered as evaporation and seepage losses in the river system (Dawn Karachi, 2000). This is a huge unrecoverable national loss and reflects on poor water resource development policy of the concerned quarters. The storage capacity of 17.1 MAF of Tarbela, Mangla and Chashma reservoirs has already declined by 4.26 MAF due to the sedimentation may further decline by nearly 6 MAF by the year 2010, which is nearly equal to the original storage capacity of the Mangla dam when it was constructed in 1967. At present, the storage capacity of our major reservoirs has already declined to 12.6 MAF, which is hardy 20 per cent of our potential storage capacity of 64.4 MAF.
The sub-soil water availability in Pakistan has dropped for 5,300 cubic meter per person per annum from 50 years to 1,100 cubic meter per person per annum at present. Though, the per capita per year water available in Pakistan is also much less than the international standards, the situation would be much more worrisome after 15 years when the availability of water would go down to 600 cubic meter water per person per annum much less than the per capita subsistence level. According to experts, as per the international standards an individual need 1700 cubic meter water per year. Pakistan is facing severe shortage of water. If the over-exploitation of the water resource is not controlled by avoiding misuse of the same, the decreasing sub-soil water level is, apparently going to aggravate the current conflict on water shortage among the provinces (Anon, 2002)
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 acre feet is transferred to canals for irrigation annually (72 per cent) and remaining 35 million acre 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 acre feet per annum. Water obtained from 531,000 public and private tubewells for irrigation purposes has been estimated at 45 million acre feet annually. Thus, the total quantum of water entering the water courses both from canals and tubewells aggregates to 122 million acre annually. Of the 145 million acre feet water entering the canals each year, about 28 million acre feet (i.e. one fourth) is lost in transit due to a number of factors. Besides, about 40 million acre feet (i.e. 40 per cent lost within the water courses themselves). Thus, only 73 million acre feet water reaches the field. Also, about 18 million acre 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 waste. 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 acre (Table 2).
To keep up the pace of agricultural growth comparable to population growth, we must bring additional lands under cultivation. In order to achieve the required growth targets in agriculture in future, we needed an estimated amount of about 155 MAF by 2005 and will need 215 MAF by the year 2015 and about 277 MAF by the year 2025 (Table 3). Since no additional water is available, it is better to improve the existing water system and land capabilities, other wise, Pakistan will be facing acute shortages of food, fiber and edible oils in near future. We must keep an eye on the issues such as inadequate management and inefficient operation of irrigation system, poor water application and unequal water distribution, depletion of ground water resources, reduction in storage capacities of existing system, and wastage of summer river surpluses and slow agricultural growth.
The irrigation system in the Indus Valley River System had been practiced through centuries and it is the prime source of Pakistan's water resources. Later on in 19th century barrages and headworks were constructed for supply of water to the agricultural lands. Now the irrigation system is comprised of three reservoirs (Tarbela, Mangla and Chashma), 19 barrages or headworks, 14 link canals, 43 number of command canals covering about 90,000 villages/chaks, more than 12,000 distributaries and about 107,000 water courses. The length of the canals is about 62,000 km with communal watercourses, farm channels and field ditches covering another, 1,600,000 km. The canal system upto distributary level is being maintained by the government through the irrigation department, whereas the operation and maintenance of watercourse is the responsibility of farmers. In the Indus Basin irrigation System, river water is directed by barrages and headworks 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 ad minors. Farmers receive water proportional to their land holdings.
Pakistan with population of about 150 million is the largest single irrigated region in the world. The total geographical area of Pakistan is 79.61 mha (Table 1). Out of 39 million acres of fertile soil, 23 million acres are irrigated by an extensive system of feeder canals. Yet, the population lives in hunger and poverty, because event has vast, fertile Indus plain cannot provide enough food, due to inefficient irrigation and farming practices. Pakistan has very poor saturate drainage and irrigation has produced 11 million acres of waterlogged land, which is not good for country. The main cause of this is that a third quantity of water is irrigated canals has seeped through their beds and has raised the water table to large extent. Pakistan has significant water resources but these are inadequate for crop production on the available land. Improved water control is important to the achievement of the full yield potential of latest recommended varieties of crops and is by far the most promising means of increasing food production. The design of irrigation systems for long-term stability must include not only engineering considerations of water storage, conveyance and delivery, but also agricultural economic considerations.
There is a need to construct small dams on river Indus, Jhelum, Chenab. The potential sites for these small reservoirs/dams need to be surveyed. However, some of these sites are located at Sehwan-Manchar lake, Hamal lake, Skardu, Bunji, Kohala, Kunhar, Rohtas, Neelam valley, Thal reservoir, etc. and these may be utilized. The levels of Mangla and Tarbela dams can also be raised to increase their storage capacity. Another option is to manage the existing irrigation system in a better way and undertake new schemes wherever possible. A considerable amount of water is lost during its conveyance due to seepage in lengthy canals, lining of the system channels could reduce these losses. As reported by WAPDA, more than 5 MAF of irrigation water could be saved by lining the minor canals only and additional amount of about 3.6 MAF could be saved by water course improvement.
A study of international climate changes indicates that the frequency of droughts is likely to increase by 50 % in the coming years. Pakistan can be a major victim of the lurking drought syndrome because for economic and political reasons it has not expanded its already inadequate and constantly declining per capita availability of surface water resources. It is noteworthy that last year, 729 water dams of various capacities and sizes were under construction in 53 countries. During the last 25 years, China and India built 45 and 25 dams, respectively. 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 the rate of 8 births per minute, 480 births per hour, 11520 per day and 4204800 per year and so on. In this way, the per capita availability of water has been constantly decreasing for the last fifty 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 that downward trend is continuing. Tarbela and Mangla dams have lost 25 % and 20 % storage capacity because of situation.
Cropping schedules are generally controlled by soils, rainfall distinction and the availability of irrigation water. The potential to improve water management is tremendous, considering the low water use efficiencies of present systems. At farm level, seepage and percolation losses are small, but surface losses resulting from insufficient attention to water management and distribution are large. Surface drainage often exceeds 50 % of the total supply during period of high rainfall. Therefore, reducing surface drainage loss offers the greatest opportunity for increasing efficiency of water use. In Pakistan, failure of electricity at peak water requirement of standing crops or when growing period sets in brings reduction in yield. This results in delay in cultural operations like preparation of seedbed, sowing, harvesting etc. Delay in operations not only upsets production plans but marketing conditions as well, bringing reduction in price and income to the farmers. The network of rivers in Pakistan carries more than twice the flow of the Nile. Half of this water is diverted into a highly developed system of irrigation canal and is used to irrigate more than 21 million hectares, which by far is the largest single irrigated mean on earth.
Scarcity of water is world wide problem, the gravity of which can be assessed from the fact that the next world war may be fought between nations on distribution of water. This is situation of the planet earth, which is 70% water, but it should also be kept in mind that less than 3 % of this water is fresh. Most of this water is either in the form of rice and snow or in deep ground water aquifers. Less than 1% of this water, which comes to about 0.01% of the earth water, is considered available for human needs and much of it is far from large population. More than 1 billion of this earth's people do not have access to safe drinking water, about 2.4 billion people lack adequate sanitation and some 3.4 million die each year from water related diseases. Inspite of these facts, proper attention has still not been paid to conserving and using the available water judiciously for domestic and agricultural purposes and the situation is specially bad in countries which are already in the water-short region.
In Pakistan, like in many other countries, precipitation exceeds rainfall and availability of water from the mountain tops and the reservoirs is depleting day by day. The situation, however, is not as bleak as it seems as with proper management of the available water, we can still manage to cope with the water shortage. This has been manifested in the past couple of years when inspite of sizeable reduction in availability of irrigation water, the yield of the crops did not reduce proportionally, we rather had surplus of wheat last year.
Water resources are critical to both economic development and the maintenance of natural systems. Every generation must, therefore, be concerned about the supply and quality of water, particularly freshwater, and about who has access to it. This is all water which human being used for their survival. Water scarcity exists for a number of reasons. The most obvious is that many places are naturally dry and rainfall is infrequent and unreliable. The world's arid areas are defined as places, where annual rainfall is less than 300 mm a year are extensive and more than 600 million people live there. Human action can cause water scarcity. Degradation of the environment for example by deforestation and overgrazing destroys the soil's ability to store water. In a well vegetated area, the soil acts like a giant sponge, absorbing rainfall and releasing it slowly. If this type of surface is destroyed heavy rains from run off the land in flash floods, to be lost to rivers, and eventually the water goes to sea.
In many parts of the world, enormous quantities of water are needed for irrigation. Other areas of low rainfall, such as the valleys of the Nile, Tigris and Indus, at least have the benefit of river water. Many parts of the world are now short of food because their populations have grown too large to be fed by locally grown crops. Expanding populations require more water. It has been reported that for the last 60 years, the demand for water by the population has been increased manifolds. Thus in 1940, the total water use was about 1000 km3 a year. It doubled by 1960, and double of again by 1990, when it reached 4130 km3 a year. Global water use is expected to increase by a further 20 per cent to 6,150 km3 by the year 2005. Heavily polluted water can lead directly to water scarcity because very dirty water is of little use unless it can be cleaned. The world's available supplies of water are becoming increasingly polluted. Today, many rivers are polluted from source to estuary the natural cleansing action just cannot cope.
Every year, some 500 km3 of waste water are released into rivers and streams. A further 6,000 km3 of clean water is needed to dilute and transport this dirty water before it can be used again. This is two- third of the world's available run off. The use of poor quality water is causing 80 % of the world sickness, because dirty water is a major cause of human disease, misery and lot of other diseases appear in the world and water borne diseases caused many deaths. It has been reported that more than 40 per cent of the population of the developing countries had no access to safe and clean drinking water and 46 per cent were without proper sanitation. Similarly, the agricultural production is also badly affected due to the presence of unwanted chemicals in the waters being used for irrigation purposes. Substances that are potentially harmful for the agricultural products and human health must be reduced or removed and substances that affect the acceptability of the water need to be controlled. In many countries, what should be fresh water is actually a potentially lethal concoction of pollutants and sewage organisms. The bacteria most commonly found in polluted water are coliforms excreted by humans. Although, coliforms themselves do not cause infections disease.
The implications of population growth are alarming because many countries are already faced with water scarcity. Average annual water use is currently about 800 m3 per person, and the world population is increasing by about 80 million people a year. Most of the population increase is in developing countries, where the demand for water is already outgrowing supply. Since both agriculture and economic activity in general depend on adequate water supply, water shortage is already slowing down rural development in many developing countries. Scarcity of water is a major constraint to the further agricultural development of arid and semi-arid regions of the world. In many countries, all the available water resources economically used have already been developed or are in process of development. The water supplies can be substantially increased mainly by using more of the world's run off or by extracting more groundwater. Attempts to increase supplies by other means such as finding a cheap way of desalinating sea water, have so far met with only limited success, although desalination plants now provide some 5 x 103 million m3 of fresh water a year to those, who can afford.
Table 1. Land resources of Pakistan area (mha)
Not available for cultivation
Table 2. Water budget for Indus Basin (million acre feet)
Average annual flow in rivers
Flows to Arabian sea
Diversion into irrigation system
Losses from irrigation system
Field application losses
Net available water for irrigation
Water pumped from tubewells
Net water available for use by crops
Table 3. Scenario of water resources of the country.
Surface water resources Annual water flow MAF
Water available at canal head (1947)
Water available at canal head (1960)
Rim Station flow (1999)
Water diverted to canals
Water flow to the sea
Losses in the river system
Ground water pumping
1. Anonymous. 2000. Dawn Karachi, September 15.
2. Anonymous. 2002. Water resources decreasing fast. Dawn Karachi, Saturday, February 22.
3. Hanks, R.J. 1983. Yield and water-use relationships: an overview. Limitations to efficient water use in crop production. Madison. WI. ASA-CSSA-SSA.
4. Massoud, F. 1981. Salt-affected soils at global scale and concepts for control. FAO. Land and Water Development Div. Tech. Paper Rome.
5. McRae, H. 1994. The World in 2020. Harper-Collins, Publishers, London, UK.
6. Todd, D.E. 1970. The Water Encyclopedia. Part Washington, N.Y. Water Information Centre.