Wars Of This Century: Water Resources
By DR. AB THAPA
Water is absolutely necessary for the very existence of human being who appeared on the earth some two to three million years ago in early Pleistocene At present the population of the world is rapidly increasing. Similarly, the demand for water for use in agriculture and industries is also constantly rising, with the result that the availability of water is already critical to future developments in many areas of our world.
It is said that water shortages would lead to international conflict as countries compete for limited water resources. In 1995 Ismail Serageldin, a top official at the World Bank, declared, “the wars of the next century will be over water.” Political tensions over water often result when different nations lay claim to the same river, lake, or aquifer. According to the UN, more than 300 river basins and aquifers worldwide cross national boundaries, creating the potential for conflict.
The Resource Base
Enormous volumes of water are involved in the global water cycle. The most comprehensive studies of the global water balance are those by a Russian scientist N.I. L’vovich. There are about 1.4 billion cu. km of water on the earth. Slightly more than 97 percent of this amount is ocean water and is therefore salty. However, because the water that evaporates from the ocean is almost free of salt, the rain and snow that fall on the earth are relatively fresh. Fresh water is stored in glaciers, lakes, and rivers. It is also stored as groundwater in the soil and rocks. There are about 36 million cu km of fresh water on the earth.
The atmosphere holds about 14,000 cu km of water at any time, while all the world’s rivers and freshwater lakes hold about 120,000 cu km. The world’s two main reservoirs of fresh water are the great polar ice caps, which contain about 28 million cu km, and the ground, which contains about 8 million cu km.
Almost all of the world’s fresh ice is found in the ice caps of Antarctica and Greenland. These ice caps cover more than 17 million sq km of land to an average depth of more than 1.5 km Most other glaciers, formed in mountain valleys at high latitudes, are tiny compared to the ice caps. If all of the ice in the ice caps and other glaciers melted, it would raise the sea level by about 80 m.
Water that flows down streams and rivers is called surface runoff. Every year about 41,000 cu km of water flows into the seas from the world’s rivers. The Amazon River, the world’s largest river, provides about 15 percent of this water. Runoff is not constant. It decreases during periods of drought or dry seasons and increases during rainy seasons, storms, and periods of rapid melting of snow and ice.
Estimating Water Demands
Humans use water for three basic purposes: agriculture, industry, and domestic and municipal use such as drinking, cooking, cleaning, and so forth. In the mid-1990s humans withdrew from rivers, lakes, and aquifers 3,750 cu km of water each year for these purposes, according to the United Nations (UN). About 2,270 cu km of that water was consumed. Examples of ways in which water can be consumed include water that evaporates from irrigated fields, becomes part of finished industrial goods, or is absorbed by a plant or animal.
Of all the uses humans have for water, agriculture has always required the most. Even today, to produce 1 metric ton of grain takes some 1,000 metric tons of water—enough to fill up three average-sized houses. According to the UN, about 70 percent of all water withdrawals in the 1990s were used for agricultural purposes. Thus agriculture consumes more water than any other use. The UN figures indicate that more than 90 percent of water used for agriculture is consumed, much of it through evaporation.
Industry, by comparison, uses far less water. For example, less than 2 metric tons of water are needed to manufacture 1 metric ton of aluminum. According to the UN, about 20 percent of water withdrawals in the 1990s were used for industrial purposes—as a coolant, a solvent, or as part of finished goods, such as soft drinks. On average, less than 4 percent of the water used by industry was consumed, with the remainder returned to rivers and lakes as discharge. Municipal and household uses drew the smallest amount, less than 10 percent of total withdrawals the UN reported.
The basic divisions of water use vary widely among nations. Industrialized nations, such as the United States and many European countries, withdraw less for agriculture and more for industry. In countries with hot climates where water is used primarily for agriculture, withdrawals of water for agriculture can be higher than the global average. Municipal and domestic usage also varies. According to the UN, a person living in Europe or North America uses between 500 and 1,000 liters of water per day. The typical person living in the developing countries of Asia, Latin America, and Africa uses between 50 and 100 liters per day. In areas where water is scarce, the figure is even lower.
Water Scarcity
The world’s population grew enormously in the 20th century. According to UN estimates, 1.65 billion people lived on Earth in 1900. By 1999 the world’s population had passed 6 billion people, and the UN estimates that it will reach 9 billion people by 2050. But the annual supply of renewable fresh water will remain constant. As the UN Commission on Sustainable Development noted, the amount of water available to each person decreases as the population grows, raising the possibility of water shortages.
Water shortages will not come all at once in every part of the world. Just as the world’s population is unevenly distributed by region, so is the annual supply of renewable water. Rainfall and snowfall are determined by uneven weather patterns and landscape, and as a result, some areas of the world get more precipitation than others.
For example, Canada is one of the largest countries in the world, with a total land area of about 10 million sq km. In the late 1990s Canada’s population was about 29 million people. In India, by contrast, about 984 million people live in a total land area of 3 million sq km. Clearly India has a higher demand for water than Canada. But Canada has more water. According to the World Resources Institute, Canada’s annually renewable water resources total 2,901 cu km per year, compared with India’s 2,085 cu km per year.
The same holds true elsewhere in the world. Brazil has more renewable water than central and southern Africa. And the combined renewable water resources of Israel, Jordan, Lebanon, Syria, and Egypt are less than that of Nicaragua alone.
This uneven distribution of water resources means that supplies in some parts of the world are already stretched thin. According to the UN, about one-third of the world’s population lived in countries with moderate to high water stress in the late 1990s. Moderate water stress means that the country is currently using 20 percent or more of its annual renewable resources. Countries in this category included Germany, India, South Africa, Spain, and the United States. High water stress means the country is using 40 percent or more. Countries in this category included Egypt, Iran, and Saudi Arabia. By 2025 the UN expects that two-thirds of the world’s population will live in countries with moderate to high water stress.
India’s Demand for Water
Like in the USA, where agriculture accounts for 83% of the total water consumption, in India also the demand for agricultural water dominates the total demand for water. India has the second largest population in the world. There are plentiful rains over most of the country but they are concentrated in a few months. As a result, India is already experiencing water scarcity. Mr. Chaturbedi M.C. has claimed that by 2005 the total ground and surface water would have been assigned to users and thus further irrigation would be restricted.
Nepalese Situation
Some years back studies were carried out in the Water and Energy Commission (WECS) to estimate the maximum potential demands for Nepal’s surface water resources and to determine how those demands compare to the supplies available The potential demand for surface water in Nepal is in the order of 1200 cu. m/s. The available supplies of all the rivers at 80% probability factor could be considered to be very close to potential demand in the absence of regulation of runoff. Thus under such condition Nepal will not have any surplus. However, after the regulation of the runoff of all the rivers the available supplies could exceed our potential demand by almost 4 times. Despite such enormous surpluses, the dry basins like the Kankai, Bagmati, West Rapti would be experiencing water shortages even after the regulation.
(The author writes on water resources)
