LETHBRIDGE, Alta. – Farmers will have to start competing with the environment and city dwellers for water supplies.
In some places, the wrestling match is already taking place, said Sandra Postel, director of the Global Water Policy Project in Cambridge, Mass.
“As water becomes increasingly scarce, we’re going to have competition for that water increase,” she said in the opening address to the Agricultural Institute of Canada, which met here recently. “And I think we’re also going to see competition between cities and farms.”
Postel said demographics suggest five billion people will live in cities 30 years from now, double the number who are urbanites today.
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And with two-thirds of the water used in the world being used by agriculture, it is likely farmers will lose out in the re-allocation.
Restoring water to streams, rivers and wetlands that was previously routed away from the environment will also be a factor in that reallocation, she said.
The tussle is already happening in California’s agriculturally rich central valley. Postel said the U.S. Congress recently passed a law dedicating 800,000 acre-feet of water that comes from the Hoover Dam to the aquatic environment and salmon fisheries. That water gets top priority.
“In a dry year, the environment get its water first and then cities and farms get their supplies after,” she said.
But as the environment and cities are clamoring for their “fair share” of water, Postel said farmers are going to be under increasing pressure to feed the world’s growing population.
In order to do that, water use will have to increase.
Postel said in the next 30 years the world’s population is projected to grow by 2.6 billion people. Using current water usage rates of 400 cubic metres per person per year, “new” water totaling one billion cubic metres will be needed.
“Where this water is going to come from is not obvious, at least for me.”
What is obvious, however, is that much of the extra food production will have to come from increased yields, largely through irrigation, since the amount of arable land isn’t increasing.
As it is, Postel said irrigation is a real cornerstone of world food security. While just 16 percent of arable land in the world is irrigated, it produces 40 percent of the food supply.
It is also obvious that security is coming at a cost. Aquifers in the United States, Saudi Arabia and India are being mined, she said.
Add to that lost productivity on irrigated land due to salinization – Postel estimates 10 percent of the world’s irrigated land base is suffering from salt build-up severe enough to begin eroding yields – and the picture looks grim.
But she said there are solutions.
“Clearly, the first line is to increase the efficiency of irrigation.”
Just 40 percent of irrigation water is used by crops, she said. The challenge will be to find ways to use the 60 percent that is now wasted.
Putting policies in place where farmers are charged the marginal cost of water – which encourages conservation – is a good first step.
Postel said that approach is already yielding results in northwest Texas where the water table in the Ogallala aquifer is falling. Farmers are converting to drip irrigation systems, decreasing their water use by 20 to 25 percent and paying those systems off in three to five years.
Another source of agricultural water may be from the very cities that want it first.
Treated urban wastewater has the potential to be used for irrigation, Postel said, something Israel is already doing. About 65 percent of its domestic wastewater is used to irrigate farmland.
Another source of water use efficiency will be through plant research, she said. For instance, new varieties of rice mature in 110 instead of 150 days, decreasing water usage.
But farmers, irrigation specialists and scientists shouldn’t have to deal with these challenges alone, Postel said. Politicians will need to realize that water scarcity and food security are linked.
