把水注入地下 以便将来使用

Water is big business in California, given the dramatic fluctuations in supply. When it rains it pours - and when it doesn't, there's drought.

Growing populations in the Western United States - and increased demands for water - are creating tensions with farmers in the sunshine state.

In California's Central Valley, green pastures and ponds full of aquatic life sit alongside expanses of arid land and dusty roads. The water in these canals and ponds has been brought in through creeks and irrigation canals in a new project that will store water in an underground aquifer for use in drier years.

The Madera Irrigation District is one of several bodies looking to store surplus water from years with high rainfall as it pours down from the nearby Sierra Nevada mountains.

Frequent droughts in the region can wreak havoc on agriculture and cause disputes between farmers and residential communities. Wet years tend to come in two or three of every ten, a surplus can cause flooding and wasted resources. To even out the flow, farmers are finding ways to store surplus water in underground aquifers.

The conclusions of extensive environmental reviews demanded the creation of temporary pools of water. This may look like a sandy stretch of land, but when exposed to rain, it abounds with water and aquatic life.

Lance Johnson, the manager of the Madera Irrigation District has been working for years to get the permits needed to recharge a regional aquifer for future use. The process required buying up a well-located neighboring ranch.

"It's a very important part of what we need to do in our state because we do have these particularly wet years when we have access to supplies, that at the particular time they are occurring we don't have demand for, and so to conserve those supplies as we are now here, we can bank those supplies for future use."

It sounds simple and logical but the proposal is fraught with problems.

Recharging an aquifer isn't quite like pouring water into a cup or filling a swimming pool - aquifers can, and do, lose water to surrounding soil. There's also the risk of contamination and potential for ownership disputes over a very slippery commodity.

Dave Clegern of the State Water Resources Control Board says the regulations governing the water supply are still pretty muddy:

"Groundwater is not regulated very tightly in California. In fact it's barely regulated in California. And, people have been pumping water out of the ground for years to supplement water they can't get on the surface during droughts. As a result those aquifers are drained down considerably. So from an environmental standpoint it makes sense to put water back into the aquifer because it frankly affects water quality. As your water goes down you get more concentrated chemicals and minerals and those sorts of things and the water simply becomes unusable after a while."

Despite the problems, Clegern believes it's a plan worth pursuing:

"The other reason it is at least popular to talk about it right now is that it's a storage issue. Building dams is very expensive, sitting reservoirs is an extremely long process, and the aquifers are there. So, pumping water into the aquifer and pumping it back out makes a lot of sense, if you're in the pumping business."

Buzz Thompson, director of the Woods Institute for the Environment, says that given all the alternatives, groundwater banking is the best option for water storage. But all the outstanding problems need to be sorted out:

"There are questions about other people pumping the groundwater out, there's the possibility that you try to pump more water out than you've actually been able to store and not lose. There are economic issues and there are environmental issues. All of those need to be addressed if we're going to make groundwater banking work."

As certain as the rain falls, drought will follow in California and, in the thirsty sunshine state, demand for water is going to continue to rise.

For CRI, I am Li Dong.