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WORLD WATER RESOURCES
Research and development activities must be focused to achieve conservation of water resources
By Dr. Syed Manzoor Alam
July 02 - 08 , 2001
World's water is finite and it is continuously recycled as a result of evaporation by the sun. Every year, the sunlight turn over about 5 x 105 km3 of water from Land Sea into water vapour free of pollution. Afterwards, the water vapour eventually returns to the surface as rain, snow, hail-storm etc. but the amount of water, which comes on the earth and the sea is not of some proportion, which is evaporated. Some 4 x 104 km3 fall on the surface, which is less than the amount evaporated from the sea. This is equivalent 18 x 102 m3 per person per years. Most of the water in the hydrosphere is salty and much of the fresh water is frozen. All over the world, water is a combination of two important gases, i.e. oxygen and hydrogen, which is generally used for life, as well as agriculture, transport, power generation and industry. Water is also being used for sanitary purposes. The water quality concern differs from place to place and often hinges social and economic growth. Water resources are critical to both economic development and the maintenance of natural systems. While, water technically does not disappear, but only changes form the quality and quantity of water resources in any place can be degraded or improved by a variety of human activities. Previous, present and coming generations are partner with each other in the care and use of water resources.
Research and development activities must be focused in generating knowledge and understanding about how to achieve conservation of water resources. Water shortage is inevitable and bound to be worsen. The best way of making sustainable use of water resources is to empower all users to manage their own supplies. We are all water users. We all therefore have a responsibility for ensuring those coming generations will live in a world, where security, not water scarcity is the norm. The amount of water on the planet is nearly 1400 million km3. Most of it 97.5 per cent (1.2 x 1018 m3) is highly saline and is of little direct use to people. Such quality water is not suitable for agriculture. The remaining 3 % (4.0 x 1016 m3) is fresh water that could be used for irrigation and other biological consumption out of which about 4.4 x 1015 m3 is made available each year for the benefit of mankind, further 1.76 % is locked away in permafrost, icecaps and glaciers.
Nearly all of the reminders are stored underground, leaving only 136,000 km3 - less than 0.4 per cent of the world's, fresh water in rivers, lakes, reservoirs, the marsh lands, soil, swamps, the atmosphere and living organisms.
The 21st century dawned with more than a billion people in developing world lacking safe drinking water. One-third of the world's population is living in countries experiencing medium water stress. Asia has the lowest per capita availability of water and by the year 2025 nearly one billion people in Asia will not have adequate access to water. In the next half century, the global population should grow until at stabilizers at around 9.3 billion. How population growth erodes water availability is shown by a survey of the Islamic Network on Water Resources Development and Management. The organization calculates that the minimum water requirement in the 21 Arable league countries is 1205 m3 per person per year and 55 m3 for domestic use and 1150 m3 for agriculture to provide an adequate diet (375 kg of fruit and vegetables, 35 kg of meat and 135 kg of meat and 125 kg of cereals per person a year). In 1985, average per capita water supply was 1750 m3 a year but even 30, 12 of the 21 countries could not meet their basic requirement. In the year 2000, the overall water availability fell to just below the basic requirement, at 1,100 m3, and to less than 600 m3 by the year 2025. Water shortage is inevitable and bound to worsen. However, the human ingenuity is such that the existing resources could be used to support populations many times larger than those of today or even those foreseen in the next century. The potential for water saving is enormous. The best way of making sustainable use of water resources is to empower all users to manage their own supplies. We are all water users. We all, therefore, have a responsibility for ensuring that future generations will live in a world where water security not water scarcity is the norm.
Though, man needs water to drink and for many other purposes, by far, the largest amount of water available must go to agriculture. Water is both the most abundant and the most important substance with which man deals. The quantities of water required for its different uses vary over a wide range. The amount of drinking water required each year, by human beings and domestic animals is of the order of 10 tons per ton of living tissues. Contrary to this, industrial water requirements for working, cooling and the circulation of materials range from one to two tons per hour of product in the manufacture of bricks to 250 tons per hour of paper and 600 tons per hour of nitrate fertilizer. Even, the largest of these quantities is small compared with the amount of water needed in agriculture. To grow a ton of sugar or corn under irrigation about 1000 tons of water must be consumed that is changed by soil evaporation and plant transpiration from liquid to vapour, wheat, rice and cotton. Fibre respectively require about 1500, 4000 and 10,000 tons of water per ton of crop.
The growing demand for food increases the importance of irrigation and drainage in the developing water where population growth is higher. Improved water control is important to the achievement of the fall yield potential of latest recommended varieties of crops and is by far the most promising means of increasing food production. There is crisis of water in many countries of the world. Human beings should think for storage of water. Therefore, building of reservoir to store water is essentially an aspect. Dams can provide stable water supplies and control floods. More than 36,000 large dams have been built since 1950. In Europe, Africa and North America, more than 50 per cent of reliable run off is already controlled in this way. New dams will still be built, but attention is now turning to other ways of increasing the proportion of run off that can be used by the human. Most of the world's freshwater is stored underground. Many countries including notably China and India rely on the exploitation of underground water resources to satisfy much of their water demand.
In many parts of the world, underground resources are now being depleted, because of reverse. This has resulted in a falling water table, wells and bore holes. The cost of pumping increases as the depth of the water table falls. There is, therefore, little scope for increasing supplies of groundwater, except in unsustainable ways. There is, however, plenty of scope for improving the sustainable management of groundwater reserves. Water is used wastefully and extravagantly in many parts of the world. Water is used once and then contaminated to pollute the source of fresh water. Literature reveals that in 1990, 65 per cent of global water use was for agriculture, 25 per cent for industry, 7 per cent for domestic or municipal use, and 4 per cent was lost from reservoirs.
Conclusion: 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 semiarid 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.
Water and salinity
Q. What is the permissible range for drinking water?
A. The permissible range for drinking water as recommended by WHO is 500 ppm or 500 mg salts/kg water.
Q. What are the three classes of underground water?
A. The three classes of underground water are usable, marginal, and hazardous.
Q. What is the quality range of usable water?
A. Whose electrical conductivity is less than 1.5 dS/cm (or 960 ppm) lmg/kg= lppm) Such water can be used directly for agriculture.
Q. What is the quality range of marginal water?
A. The quality range of marginal water is with EC of 1.5 to 3 dS/cm or 960 to 1920 ppm .Such water cannot be used directly for agriculture, because of higher concentration of salts and have to diluted with sweet waters.
Q. What is the range of hazardous water?
A. The range of hazardous water is 3 dS/cm and above. This quality of water is totally unsuitable for agriculture.
Q. What in the EC of Indus water?
A. The EC of Indus water is about 1.0 dS/cm or nearly 700 ppm.
Q. What is the quality of a non-saline or a good soil?
A. The soil whose EC is less than 4 dS/c~m (2560 ppm).All sorts of crop can be grown.
Q. What is a saline soil?
A. Saline soil having EC greater than 4 dS/cm, pH below 8.5 and ESP( exchangeable sodium percentage) less than 15, contain chlorides and sulphates of sodium, calcium and magnesium. This quality of water is totally unsuitable for agriculture.
Q. What are the marginal soils?
A. Soils with EC about 8- 15 dS/cm(or 5120-9600 ppm) are marginal soils—Crops like sorghum, barley, canola, mustard, spinach, sugar beet, guar, dhancha, Berseem, lucerne, sweet clover, fig, grape etc. can be grown.
Q. What are the hazardous soils?
A. Soils having EC 15-20 dS/cm or (9600-12800 ppm) are marginal soils—Crops like Date palm, coconut, kallar grass orchard grass, Bermuda grass and Sudan grass, Wood species like Jojoba, guava, mesquite, Acacias. Atriplex, Life plant, Aloe veera, Bottle palm, China rose, Banana, Senna, Cactus etc. Can be grown . Some of them consume enough quantities of water to affect the ground water level.
Q. What is the total land area of Pakistan ?
A. The total land area of Pakistan is 79.6 mha.
Q. What is the total land area of Punjab?
A. The total land area of Punjab is 20.60 mha.
Q. What is the cropped area of Punjab.
A. The cropped area of Punjab is 11.04 mha (56% of total land of the country).
Q. What is the total land area of Sindh?
A. The total land area of Sindh is 14.10 mha. of which 5.45 mha. is cropped (27.50%) of the total land area of the country.
Q. What is the total land area of NWFP?
A. The total land of NWFP is 10.20 mha. of which 1.93 mha is cropped (9.7% of the country)
Q. What is the total land area of Balochistan?
A. The total land area of Balochistan is 34,70 mha, of which only 1.40 mha (7.06%) is cropped.
Q. What is the strength of cropped area in the country?
A. The strength of cropped area is about 20 mha. Or 25 .5% of the total land area is under cultivation
Q. How much cropped area is under irrigation in the country?
A. About 15.2 mha or about 75 % land is under irrigation.
Q. How much area is under rain-fed?
A. About 4.25 mha. or 19% of the land is under rain-fed. About 4% lands irrigated by tube-well
Q. How much area of Pakistan is under salt-affected?
A. About 6.3x103 mha. of land is under salt-affected.
Q. How much area of Punjab is under salt-affected?
A. About 3.28 mha. area of Punjab is salt-affected.
Q. How much area of Sindh is salt-affected?
A. About 3.06 mha. of land is under salt-affected
Q. How much land of NWFP is salt-affected ?
A. About 0.61 mha. of land in NWFP is salt-affected.
Q. How much land of Balochistan is salt-affected?
A. About 0.1 mha. of land in Balochistan is salt-affected.
Q. How we can improve salt-affected land?
A. We can improve salt-affected land by- scrapping of salt layer, ii) by land Raveling. ii) deep ploughing, iv) sub-soiling, v) sanding, vi) flushing the salt-affected land with good quality water and drainage, vii) application of higher seed rate for higher plant population. By Manuring through legumes, application of farm yard manure, gypsum and sulphuric acid.
Q. What is the range of salt-affected soils of the world?
A. The ranges of total salt-affected soils of the world are about 925 million hectares.
Q. What is the range of salt -affected soil in Asia.?
A. The range of salt-affected land in Asia is 316.50 mha.
Q. What is the range of salt-affected land in Europe?
A. The salt-affected is about 50.80 mha.
Q. What is the range of salt -affected land in Africa?
A. At the range of salt-affected land in Africa is about 80.54 mha.
Q. What is the range of salt-affected land in Australia?
A. The range of salt-affected land is Australia is 357.3 mha.
Q. What is the range of salt-affected land in North America?
A. The range of salt affected land in North America is about 17.72 mha.
Q. What is the range of salt-affected land in South America?
A. The range of salt-affected land in South America is 129.2 mha.
Q. What is the range of salt-affected land in India?
A. The range of salt-affected land in India is about 7 mha. (The total land of India is more than 4 times greater than the area of Pakistan)
Q. What is the range of salt-affected land in Pakistan?
A. The range of salt -affected land of the country is more 6.0 mha, of which 4.2 mha is located in Indus Basin.
Q. How much area in Pakistan is affected by waterlogging and salinity?
A. The area affected by waterloggng (water table within 5 feet) is 2.339 mha, while area affected by soil salinity is about 2.55 mha.