Think tank solutions run dry in our valley

last updated: September 13, 2008 09:21:57 PM

Most likely, the Pacific Institute is sincere in suggesting ways to save water. Last week, the Oakland-based think tank issued a study that said if valley farmers would just be a little water-wiser, the state could save a lot of liquid. The co-authors even suggested that 20 reservoirs could be filled with the water saved by simply using better conservation methods down on the farm.

So why build even two more reservoirs -- as Gov. Schwarzenegger, Sen. Dianne Feinstein and many who depend on water are urging -- when all we have to do is re-educate a few wasteful farmers?

Perhaps the study's conclusions are applicable in some areas of the valley, but if we followed all of co-author Peter Gleick's suggestions around here, we could end up with thousands of thirsty city dwellers and ruined cropland.

Many of our farmers flood irrigate -- the very practice the Pacific Institute finds so wasteful. By switching to sprinklers and drip systems, says Gleick, farmers could save millions of gallons that then could be used to water the lawns of city dwellers. While true, it doesn't tell the whole story.

Flood irrigation does more than simply help tomatoes, peaches, walnuts, almonds, alfalfa and hundreds of other crops grow. It is also crucial for replenishing our underground aquifer -- the largest source of fresh water for everyone.

Modesto pumps 60 percent of its residential water from underground. Turlock gets 100 percent of its water underground, as do Ceres, Riverbank, Oakdale and most other cities. Some cities, such as Stockton, depend too heavily on wells and have overdrafted their aquifer and now are forced to buy water from others. If there's none to sell and the wells go dry, people will go thirsty.

Irrigation helps ensure that won't happen around here.

"It's very complicated," said Vance Kennedy, a retired hydrologist and farmer near Modesto. But it starts with the dirt, he said. Fields even only a few hundred yards apart can have very different soil characteristics. Some soil is sandy, allowing water to soak in quickly. Other soils have more clay, causing water to sit longer where it either nourishes plants or evaporates. The soil mix can change at different depths. Our area has many soil types, but most are fairly permeable -- meaning some of the irrigation water nourishes plants and some recharges the aquifer. Over time, we end up drinking that water.

But we wouldn't drink it if it were salty -- and neither would plants. Water flowing from the mountains often contains mineral salts. When water is put on soil in small amounts, plants soak up most of it -- just as the scientists at the Pacific Institute prefer. But when applied more sparingly, water doesn't soak far into the soils and the salts are left near the surface. Enough salts can turn even rich soil sterile. On the other hand, flooding the soil dilutes the salts and pushes them past the root zones, keeping the dirt fertile.

New irrigation methods are being developed to use saltier water, but for now it remains a problem on less permeable soils.

In Monday's Sacramento Bee, Gleick offered suggestions for solving the state's water problems, including "new water-rate structures" to encourage efficiency and better enforcement of California's water rights laws. Such suggestions often ignore the legal rights of those who built the dams to capture the water in the first place.

Faced with a water emergency, we're being offered lots of ideas. Professor David Zetland from the University of California at Berkeley, for instance, points out that farmers aren't stupid and should be given the freedom to sell water allocations -- which brings up a whole new level of issues. And while some of the suggestions offered by the Pacific Institute will work here, others simply will not.

There is no shortage of ideas for better use of our water. But there is a shortage of water. And until we find better ways to capture more than we do now, plans to conserve it won't amount to much.

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