THE worst recorded drought in California鈥檚 history has forced state regulators to restrict people鈥檚 water use by a quarter. In the long-run, though, climate change and limited supply mean the state must radically change the way it manages water, particularly below ground.
The state normally depends on winter storms to replenish its water. Most climate models suggest these storms will become less frequent but more intense, says , a climatologist at the Scripps Institution of Oceanography in San Diego. So water will come in huge, sudden gushes, possibly bringing more than existing infrastructure can capture. 鈥淵ou鈥檙e either in a drought or in a flood,鈥� says of the University of Texas at Austin. 鈥淲hat you really need is storage to even that out.鈥�
The traditional method of storage is to create a reservoir by damming a river. But dam-building is expensive, can be environmentally damaging, and most of the good spots are already in use. An alternative is to push water underground using recharge ponds or injection wells. Recharge ponds are constructed surface basins that allow water to collect and seep through the soil; injection wells use high-pressure pumps to actively push water down into aquifers.
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Kern County, in the south of California鈥檚 vast, central Joaquin valley, has already reaped the rewards of managing its groundwater. With its surface water supply becoming increasingly unreliable, the county began to look for alternatives. It gave up huge chunks of agricultural land and started using it as recharge pools.
Water accumulates in wet years and drains into the depleted aquifer below. In the dry season, when the pools are empty, winter wheat is sown. Its roots break up the soil and improve drainage in readiness for the next batch of water.
Around 1.2 trillion litres of water collected this way helped alleviate the effects of the current drought, says Jim Beck, general manager of the Kern County Water Agency. 鈥淲ithout that we鈥檇 have had much more farming land go out of production.鈥�
Further north, a pilot project by the University of California has bulldozed levees along the Cosumnes river, allowing water to flow over the surrounding flood plains. As a result, a small storm in February pushed hundreds of millions of litres of water into the aquifer below 鈥� far more than normal.
Groundwater management has several advantages over other methods. or desalinating water. What鈥檚 more, aquifers lose no water through evaporation, do not flood ecosystems, and in California they have capacity for between 17 and 26 times as much water as all of the state鈥檚 reservoirs combined.
鈥淐alifornia needs to get a grip on its groundwater,鈥� says Bill Alley, the director of science and technology for the National Ground Water Association. 鈥淭here鈥檚 no doubt of that.鈥� That might now be starting. Last year, California鈥檚 governor Jerry Brown announced $1.5 billion to increase the state鈥檚 storage capacity. Almost all of the districts in line for such funding sit atop overdrawn aquifers and could make use of them with new funding.
This article appeared in print under the headline 鈥淩efill aquifers to quench drought鈥�
