Fresh water is essential to life on earth. Yet, today 1.2 billion people lack safe drinking water and 2.4 billion lack access to basic sanitation. United Nations officials say that if we continue with business as usual, two-thirds of the world's population will be living in moderate to severe water stress by 2025. Why are some nations water starved? What is the impact of water scarcity on food production? And, what must the world community do to address these problems? In this second of a four part series on water scarcity, VOA's Rosanne Skirble discusses these issues with water expert Sandra Postel, author of "Pillar of Sand: Can the Irrigation Miracle Last?"
Forty percent of the world's food supply depends on irrigation made possible through a network of canals, wells, dams and reservoirs. Irrigation has also boosted crop yields and opened new lands for farming.
In Pillars of Sand: Can the Irrigation Miracle Last? Sandra Postel says that while we live on a water-rich planet, fresh water is not evenly distributed. She says that more and more farmers - especially in regions of the world dependent on irrigation - are coming up dry.
Postel: "Look at the global numbers. Asia has 60 percent of the world's people, but only about 36 percent of the renewable fresh water. So, even on a continental scale, it is clear that water is a serious constraint in Asia. China, India and Pakistan are three of the four top irrigators in the world. The United States is the other one that makes up that top four. Each of those three Asian countries has serious water problems in each of its major zones of irrigated agriculture. Rivers are running dry. Ground water is being over-pumped extensively in order to meet current demands for food production, and soils are becoming salinized. Salt is building up in the soil as a result of irrigation practices in a dry climate. Asia has in most areas of agriculture a monsoon climate, and there might be abundant rainfall during the wet season and then a very long dry season where crop production depends very heavily on irrigation water."
Skirble: "Why are these rivers and wells running dry? Isn't the earth like a big water-recycling machine?"
Postel:"Water is renewable. Freshwater is a renewable resource, but it is also finite, which means that there is only so much available at any given place and time. As long as your demands for water don't exceed that renewable supply, that finite supply, things are generally okay and the water is renewed. But if your demands exceed that renewable supply, then you are in the situation that you are over-pumping groundwater to satisfy the demand, or taking too much water from river basin systems. Groundwater is a very important source of irrigation for farmers, but in most places where you look where it is important, it is not being used and managed in a sustainable way. And that is a serious concern for future food production, because you can not over-pump ground water indefinitely."
Skirble:"You say 'used in a sustainable way.' What are some of the things that can be done and are being done?"
Postel:"A top priority in my view is to begin irrigating more efficiently. There are a number of technologies available that can allow farmers to irrigate their crops, provide the water requirements of their crops in a more efficient way. One example would be "drip irrigation," which is just about the most efficient technology in existence for irrigating crops and it is only used on one percent of irrigated land worldwide. Now, it is not practical to irrigate wheat or rice with drip irrigation, but you can irrigate cotton and sugarcane and most fruit and vegetable crops and orchard crops, and compared with more conventional means of applying water to a field using gravity methods, irrigation with drip methods can often achieve efficiencies of 95 percent, reducing dramatically the amount of waste and unproductive use of water on the field. With the grain crops there have been good increases in efficiency with the use of sprinkler irrigation technologies. And even where gravity systems are in use, better [water] management -- leveling of the fields, (for example) -- better management techniques can again improve efficiency."
Skirble: "What about switching to less water-intensive crops?"
Postel: "That's another important method that we do need to make more use of. Many crops around the world are grown in climates that are not appropriate to those crops, and so there is a lot of water required to grow cotton or rice in very dry climates where those crops may not be appropriate to production there. So, better matching of the growth of crops with the climate that is in those regions could help make more efficient use of water."
Skirble: "What about competition for water? Competition from cities, especially, as the population grows and more people shift from the countryside to cities."
Postel: "This is becoming a very large new challenge for water management. The fact that as water becomes scarce, you simply cannot abide the old solution of going out and building a new dam, drilling new water wells and constantly increasing the supply. The name of the game increasingly becomes reallocation, which means taking the water supply that is already developed and figuring out how you are going to reallocate it. Cities and industries tend to have a higher value for the water in their uses. Water tends to generate 50 to 100 times more economic value [when it is] used in industries than it does [when it's used] in agriculture. So as water becomes scarce from an economic sense, it usually makes sense to move that water from irrigated agriculture over to cities. But, of course, it is not that simple, because especially in developing countries, maybe 70, 80, 90 percent of people living in those countries are in agriculture. Their lives depend on agriculture. It is not a simple matter of shifting water in those situations. And, even in the United States, there is currently major competition between cities and farms that is quite acrimonious. So, this will be a difficult problem. Some advocate the use of [water] markets to do this and that may work or help to do this reallocation. In other cases governments control the allocation of water. How you do this fairly and equitably and keep rural livelihoods intact is a big challenge. And increasingly, the issue will be how to reallocate it, not how to generate more of it."
In Pillars of Sand: Can the Irrigation Miracle Last? Sandra Postel contends that the solution to water scarcity hinges on the ability to do more with less water. She writes that new technologies and policies "can double water productivity needed to satisfy food, water and environmental needs of the next several decades, if we so choose." The time to act, she says, is now.
For more information on Pillar of Sand: Can the Irrigation Miracle Last? and other books and articles by Sandra Postel, check out the World Watch Institute at World Watch.org
In the next report on gloabl water scarcity, VOA's Rosanne Skirble examines the serious, but often overlooked problem, of over-pumping of groundwater.