June 2010
Water Management By Bill Schaefer

Look at on-farm conservation, irrigation practices to best use water supplies

There’s a finite water supply these days and growers are finding the supply chain becoming ever tighter, but they haven’t reached the depths of despair yet.

Sufficient water is available for most growers this year, except in the Klamath basin, where allocation is so tight that some growers are relocating their operations.

The difficulty facing growers is how to best conserve and husband this most valuable natural resource.

Steve Howser, manager of the Aberdeen-Springfield Canal Co. (ASCC) in Aberdeen, Idaho, has some tips on how to use your water most efficiently.

According to Howser, ASCC diverts 325,000 to 350,000 acre-feet annually from the Snake River, and of that amount, 180,000 acres leaches in to the aquifer.

According to Howser, this year’s snowpack and runoff forecasts are very similar to 2001, when they ran out of natural flow water on June 11 and had to shut the canal off for 21 days in August to save enough storage water to get through harvest.

There is a difference, though.

The difference between now and 2001 was when we began drawing our storage in 2001 we only had about 31 percent of our storage available,” Howser said. “This year, we’re probably going to have about 95 percent of our total storage available.”

Based on the 30-year average of normal water demand, Howser expects to see about 10 percent of storage water remaining at the end of the 2010 water year to carry over to 2011.

“That means that my job is to save as much of that storage water as possible.”

On-Farm Conservation

Howser sees conservation as a multi-tier effort, with the first tier coming from on-farm conservation.

His advice to farmers seeking greatest efficiency in water use is to make sure the nozzles on their irrigation equipment are correctly sized, and to fix leaks.

“Leaky mainlines, leaky joints in wheel lines are a larger waste of water than a lot of folks think,” he said. “Replace your gaskets.”

Howser said the most important conservation measure irrigators can take is to give as much advance notice as possible for turn-ons and turn-offs.

“If possible, I’d like to have 72 hours notice before you need the water and 24 hours notice before you shut off,” he said.

Communicate with your ditch rider, advises Howser. Let him know when you’re going to be drawing water and he’ll communicate with the canal manager, thereby creating the most efficient use of one of the most precious of ag commodities.

Lyle Swank, water master of Water District 1, the largest water district in Idaho, echoes Howser’s recommendation to give advance notice when drawing water.

“In Water District 1, we’ve required 24-hour-notice when somebody calls in water, and part of that is to cover the travel time to get down there,” Swank said. “We don’t want to have all your storage water end up below where you can use it.”

Of equal importance is to give advance warning when shutting your water off, Swank said.

Soil Monitoring

Rick Allen, a research professor specializing in water resources at the University of Idaho’s Kimberly Research and Extension Center, advises growers to monitor their soil when water is tight.

“When water is tight you definitely don’t want to overwater, so people ought to be monitoring their soil,” Allen said. “There are a variety of ways to do that.”

Allen advises those with center-pivot watering systems to slow the pivot down to avoid water loss through evaporation, until the plants build up their canopies that will cover and shade the soil, helping suppress evaporation.

“One way to save water, and it’s a true savings, is to reduce the water that evaporates from the soil,” Allen said. “Because every pass around the field wets up the soil and you can lose up to half an inch of evaporation off the surface of the soil – and that’s especially important before the crop fully covers the soil.”

But there are two things you have to balance. If you have a light soil that doesn’t hold water, you can only slow it so much or the soil will tend to dry up between pivot passes. You don’t want your tubers getting stressed, he said.

The other thing to watch is runoff.

“The other thing we advise growers is that ‘slow that pivot down until you start to see runoff and then speed it up a little bit,'” Allen said. “You’re balancing between evaporation loss or runoff loss, and they’re both water consumers.”

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