Healthy soil and sustainable growing

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To Prevent a Food Crisis, We Need to Increase Water Efficiency
Since it takes 1,000 tons of water to produce 1 ton of grain, it is not 
surprising that 70 percent of world water use is devoted to irrigation -- a 
practice we can do better.
June 24, 2010  |  By  Lester R. Brown
 
http://www.alternet.org/food/147296/to_prevent_a_food_crisis%2C_we_need_to_increase_water_efficiency?page=entire

With water shortages constraining food production growth, the world needs an 
effort to raise water productivity similar to the one that nearly tripled 
land productivity over the last half-century. Since it takes 1,000 tons of 
water to produce 1 ton of grain, it is not surprising that 70 percent of 
world water use is devoted to irrigation. Thus, raising irrigation efficiency 
is central to raising water productivity overall.

Data on the efficiency of surface of water projects—that is, dams that 
deliver water to farmers through a network of canals—show that crop usage of 
irrigation water never reaches 100 percent simply because some irrigation 
water evaporates, some percolates downward, and some runs off. Water policy 
analysts Sandra Postel and Amy Vickers found that "surface water irrigation 
efficiency ranges between 25 and 40 percent in India, Mexico, Pakistan, the 
Philippines, and Thailand; between 40 and 45 percent in Malaysia and Morocco; 
and between 50 and 60 percent in Israel, Japan, and Taiwan."

Irrigation water efficiency is affected not only by the type and condition of 
irrigation systems but also by soil type, temperature, and humidity. In hot 
arid regions, the evaporation of irrigation water is far higher than in 
cooler humid regions.

In a May 2004 meeting, China's Minister of Water Resources Wang Shucheng 
outlined for me in some detail the plans to raise China's irrigation 
efficiency from 43 percent in 2000 to 51 percent in 2010 and then to 55 
percent in 2030. The steps he described included raising the price of water, 
providing incentives for adopting more irrigation-efficient technologies, and 
developing the local institutions to manage this process. Reaching these 
goals, he felt, would assure China's future food security.

Raising irrigation efficiency typically means shifting from the less 
efficient flood or furrow systems to overhead sprinklers or drip irrigation, 
the gold standard of irrigation efficiency. Switching from flood or furrow to 
low-pressure sprinkler systems reduces water use by an estimated 30 percent, 
while switching to drip irrigation typically cuts water use in half.

As an alternative to furrow irrigation, a drip system also raises yields 
because it provides a steady supply of water with minimal losses to 
evaporation. Since drip systems are both labor-intensive and water-efficient, 
they are well suited to countries with a surplus of labor and a shortage of 
water. A few small countries—Cyprus, Israel, and Jordan—rely heavily on drip 
irrigation. Among the big three agricultural producers, this more-efficient 
technology is used on 1-3 percent of irrigated land in India and China and on 
roughly 4 percent in the United States.

In recent years, small-scale drip-irrigation systems—literally a bucket with 
flexible plastic tubing to distribute the water—have been developed to 
irrigate small vegetable gardens with roughly 100 plants (covering 25 square 
meters). Somewhat larger systems using drums irrigate 125 square meters. In 
both cases, the containers are elevated slightly, so that gravity distributes 
the water. Large-scale drip systems using plastic lines that can be moved 
easily are also becoming popular. These simple systems can pay for themselves 
in one year. By simultaneously reducing water costs and raising yields, they 
can dramatically raise incomes of smallholders.

Sandra Postel estimates that drip technology has the potential to profitably 
irrigate 10 million hectares of India's cropland, nearly one tenth of the 
total. She sees a similar potential for China, which is now also expanding 
its drip irrigated area to save scarce water.

In the Punjab, with its extensive double cropping of wheat and rice, 
fast-falling water tables led the state farmers' commission in 2007 to 
recommend a delay in transplanting rice from May to late June or early July. 
This would reduce irrigation water use by roughly one third, since 
transplanting would coincide with the arrival of the monsoon. The resulting 
reduction in groundwater use would help stabilize the water table, which has 
fallen from 5 meters below the surface down to 30 meters in parts of the 
state.

Institutional shifts—specifically, moving the responsibility for managing 
irrigation systems from government agencies to local water users 
associations—can facilitate the more efficient use of water. In many 
countries farmers are organizing locally so they can assume this 
responsibility, and since they have an economic stake in good water 
management, they tend to do a better job than a distant government agency.

Mexico is a leader in developing water users associations. As of 2008, 
farmers associations managed more than 99 percent of the irrigated area held 
in public irrigation districts. One advantage of this shift for the 
government is that the cost of maintaining the irrigation system is assumed 
locally, reducing the drain on the treasury. This means that associations 
often need to charge more for irrigation water, but for farmers the 
production gains from managing their water supply themselves more than 
outweigh this additional outlay.

In Tunisia, where water users associations manage both irrigation and 
residential water, the number of associations increased from 340 in 1987 to 
2,575 in 1999, covering much of the country. As of 2009, China has more than 
40,000 water users associations to locally manage water resources and to 
maximize water use efficiency. Many other countries now have similar bodies. 
Although the first groups were organized to deal with large publicly 
developed irrigation systems, some recent ones have been formed to manage 
local groundwater irrigation as well. Their goal is to stabilize the water 
table to avoid aquifer depletion and the economic disruption that it brings 
to the community.

Low water productivity is often the result of low water prices. In many 
countries, subsidies lead to irrationally low water prices, creating the 
impression that water is abundant when in fact it is scarce. As water becomes 
scarce, it needs to be priced accordingly.

A new mindset is needed, a new way of thinking about water use. For example, 
shifting to more water-efficient crops wherever possible boosts water 
productivity. Rice production is being phased out around Beijing because rice 
is such a thirsty crop. Similarly, Egypt restricts rice production in favor 
of wheat.

Any measures that raise crop yields on irrigated land also raise the 
productivity of irrigation water. For people consuming unhealthy amounts of 
livestock products, moving down the food chain reduces water use. In the 
United States, where the annual consumption of grain as food and feed 
averages some 800 kilograms (four fifths of a ton) per person, a modest 
reduction in the consumption of meat, milk, and eggs could easily cut grain 
use per person by 100 kilograms. For 300 million Americans, such a reduction 
would cut grain use by 30 million tons and the need for irrigation water by 
30 billion tons.

Bringing water use down to the sustainable yield of aquifers and rivers 
worldwide involves a wide range of measures not only in agriculture but 
throughout the economy. The more obvious steps, in addition to more 
water-efficient irrigation practices and water-efficient crops, include 
adopting more water-efficient industrial processes and using both more 
water-efficient household appliances and those that use no water at all, such 
as the new odorless dry-compost toilets. Recycling urban water supplies is 
another obvious step in countries facing acute water shortages.