NRDC and the Pacific Institute just released a report purporting to show the potential for large water savings in California in the face of our severe drought. While laying out the technical potential in a static setting is a useful exercise, this report can be misleading about the true potential for water savings without significant institutional and political change. The report doesn’t account for how farmers actually respond to improved irrigation efficiencies, and how residential customers resist changing their landscapes and using recycled water.
Starting with farmers, we found in a study on the benefits of aggregating PG&E’s agricultural accounts that growers were using subsurface drip systems increase tomato yields by as much as 50%. In Fresno County, processed tomato yields have risen 26% in 5 years as flood irrigation has been replaced by drip. In addition, the amount of runoff has been reduced, so on net the new efficient irrigation technologies have lead to increased productivity with no reduction in water use.
Residential customers are resistant to the idea that they should give up their lush landscaping. As I posted previously, even in environmentally-friendly Davis, voters rejected a new rate structure that would have encouraged summer water conservation. And they are just as thrilled with using recycled water. A 2004 SDCWA survey found that 63% of residents didn’t want recycled water introduced into their drinking water. All of this adds up to political resistance to change that water professionals see as a “no-brainer.”
Another question is what happens to the downstream and groundwater basin users who now depend on runoff for their water supplies? Particularly in agriculture, water is often reused several times as it drains or percolates to the next user. Calculating the true potential savings requires a full water-budget analysis of a basin, not just adding up all of the individual savings without considering the synergism among them.
And finally, what happens to the ability to respond to variations in water conditions? Urban water agencies are already concerned about “demand hardening.” Farmers have moved to higher yield, more profitable orchard crops, but as a result they can’t easily accommodate large swings in water availability. Managing our water supply isn’t just about reducing the average consumption–it’s about creating a less vulnerable system.
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Here’s an article in the Bee by Jay Lund et al on the “myths” of the California’s water situation. They agree in their second point with my statement here. Their first point comes from a study released in May showing drought impacts that Lund and Richard Howitt did. We confirmed their groundwater pumping levels with data we had on swings in PG&E’s agricultural electric loads.
Here’s a working paper (also published in JEEM) that finds in Kansas that moving from sprinklers to drip increased groundwater extraction due to the economic gains from improved productivity. It’s this sort of economic behavior that needs to be considered in looking at water management strategies, not just simplistic engineering calculations.
Click to access PfeifferLin_irrigationtechnology.pdf