Saving The World, Drip By Drip
Ten years ago, World Bank VP Ismail Serageldin said "If the wars of this century were fought over oil, the wars of the next century will be fought over water." Though some people at the UN disagree, there is no question that water scarcity is a looming problem of our time.Posted by Jeremy Faludi at August 6, 2006
What many urban greens don't know is that solving the world's water problem requires solving the irrigation problem. Both in the developed and undeveloped world, irrigation is a boon to agriculture, and in some ways a boon to sustainability, allowing farmers to increase production of their land without having to convert more forests or other wild areas into cropland. However, inefficient irrigation wastes more water than all the people of the world use (efficiently or inefficiently) for all their drinking, bathing, manufacturing, and industry. By a long shot. Worldwide, 70% of all water use is agricultural irrigation, according to the UN World Water Development Report. (22-23% is used for industry, and the remaining 7-8% is domestic use.) In the US, irrigation uses 80%, and in the dry western states 90%, according to the USDA. What's more, the UN's World Water Assessment Program says that almost 60% of irrigation water is wasted. (These and many other impressive statistics at International Water Management Institute and Earth Policy Institute.) Usage and efficiency differs from country to country, but to give you an idea of scale, the unit of measure for irrigation in the US is an acre-foot: the amount of water required to fill an acre of land one foot deep. (That's about 1.2 million liters.)
Why does all this irrigation water get squandered, and how can it be fixed?
For poor farmers, irrigation water is usually squandered by lack of infrastructure--bringing water from river or dam to field using canals without linings or covers, which would prevent water soaking into unfarmed soil or evaporating into the air. Since most of the world's poorest people are farmers, they are also the people who suffer the most from inefficient water use, because they are the last ones to get clean safe drinking water. The solution to this is smart investment, which some government programs and micro-credit organizations and are making possible, but funding is wanting. India was the cradle of modern irrigation technology while under British rule, with a mix of public and private funding for waterworks projects (as well as a mix of success and failure, according to a nice paper on the history & its lessons for today). India could now become the cradle for the next generation of water-efficient micro-scale irrigation if they put their minds to it.
For rich farmers, water is usually squandered by the tragedy of the commons. Most countries--including developed ones--lack water-rights laws that charge for water usage. In fact, most rich countries have laws that say "use it or lose it" and "first in time, first in right", which actually encourage farmers to use as much water as they can, even when they don't need it. City dwellers are used to paying for water, but they are paying for their water delivery, not their actual water consumption; irrigators do not pay by the liter as urbanites do. Changing water rights laws, or shifting taxes to charge for water consumption, would help align price incentives with resource scarcity. The Canadian government's Policy Research Initiative found that simply measuring irrigators' water usage (no fees, just metering) caused them to reduce usage by 10%, and introducing a price penalty for exceeding water allotments caused an additional 22% reduction. Aggressive price changes (which could include rebates for low-volume users as well as fees for high-volume users) could easily cause much larger changes in usage.
The irrigation problem will become bigger
in coming decades: the World Bank estimates that population growth will
require global agriculture to double its production in the next thirty
years, and as developing countries lift themselves out of poverty,
consumers' appetite for water-intensive foods like meat tend to
skyrocket. But with clever policy incentives and infrastructure
improvements, the world could double irrigation without using any
more water than today. We might even be able to use less. According to
Institute, California used less water in 2001 than it did in 1975,
despite population growth of 60% and a 2.5x increase of gross state
product. The "soft path" to avoid catastrophe in water supply
is not only possible, it is already being done in some places.
How can farmers reduce water usage? The first part of the solution is to choose crops and animals that require less water (for instance, raising 1kg of beef uses 15 to 30 times as much water as growing 1kg of grain). But the real burden here is on consumers making their food choices. Farmers need to grow what sells, or they go out of business; consumers ultimately decide what crops are grown.
Assuming that farmers are growing what they need to grow, agricultural water use can still be cut in half or better by choosing the right irrigation system.
Drip irrigation, first tried in Germany in the 1800's and then brought to its modern incarnation in Israel in the 1960's, is the most efficient method of delivering water to a plant's roots. Running water through open ditches or canals (called "surface irrigation") allows water to evaporate into the air and soak into the ground; spraying water through the air with sprinklers is effective in humid climates, but can cause up to 45% evaporative loss in desert climates. Drip irrigation instead uses pipes with tiny holes or channels in them (or pipes of porous material) that let a controlled amount of water drip from the pipes in certain places directly onto the ground. Some systems are even buried below ground to prevent any evaporation. Drip irrigation is especially good for trees and shrubs that don't require tilling of the soil, but the system can be used anywhere. Though it can be more expensive to use than sprinklers or surface irrigation, it can also improve uniformity of water distribution, which keeps crop quality high.
Other techniques are also important. Scheduling,
for instance: watering more or less in different parts of the season,
compensating for weather; and if evaporation is an issue, watering at
night to reduce losses from the heat of the day. While use of greywater
for irrigation is only an option for urban gardens and landscaping,
cropland irrigation systems could return runoff from the bottom of a
sloped field to the top to be used again. This would also lessen the
runoff of fertilizers or pesticides into rivers and groundwater.
Mulching and other techniques can also reduce evaporation.
Paying For Water
With drip irrigation, we know that the technology exists for saving water. Since it hasn't been used much, clearly we also need some incentives. The most obvious is making water cost money.
British Columbia taxes water consumption
at varying rates, as low as $20 per acre-foot (about 1.6 cents per 1000
liters). According to Sightline Institute's book Tax
Shift, if the US state of Idaho (a particularly dry state) enacted a
similar tax, it could cut its sales tax in half, and even if all the
farmers' additional costs were passed on to consumers, the reduction in
sales tax would decrease food prices more than water taxes would
increase them. If monitoring agricultural water usage were seen as too
burdensome, the tax could be placed on water rights instead, giving
farmers an incentive to use less water so they can sell the remaining
rights to others. Another possible incentive structure would be water
markets, where the government decrees a certain amount of water use is
allowed annually, and the right to use it is bought and sold among
users. Such markets have proven very effective incentives for carbon
emission reductions, and many policymakers argue that they work better
Most small farmers today, even in rich nations, are barely making ends meet, and thus lack the cash to invest in infrastructure such as drip irrigation. At the same time, some green office buildings spend significant amounts of money putting in rainwater catchment systems, low-flow toilets and other fixtures, etc. What if, instead, a building developer bought a farm a drip irrigation system (and perhaps even provided for its maintenance & upkeep with an endowment or other service contract)? An entire subdivision may use 8000 gallons per day, and making all the houses super-water-efficient like BedZED might reduce that to 2600 gallons per day; but a California farm may use 2.6 acre-feet per acre per year (over 2300 gallons per day, per acre). So a hundred-acre farm (the size of about four city blocks on a side, square; roughly as big as a small subdivision) would use 230,000 gallons per day. Even reducing that farm's water use by 3% causes more water savings than reducing a normal subdivision's water use by 60%. Installing a state-of-the-art drip irrigation to reduce the farm's water use by 50% would save 115,000 gallons per day, which is over 19 times what the BedZED-style water saving would achieve in the subdivision.
William McDonough once told a building developer to plant ten square miles of forest to offset greenhouse emissions for the building being built. It's time for an architect to tell the developer they're buying drip irrigation for ten square miles of California farmland. Assuming that reduced water use by 50%, it would save almost 7.4 million gallons per day--enough LEED credits to last the rest of their career.