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If You Can’t Raise the River, Modernize the Canal

• August 06, 2008 • 11:30 PM

Caught between a rock and dry place, California tries automating farm water delivery.

Astride the maze of rivers east of San Francisco that crisscross California’s Sacramento-San Joaquin Delta stand two imposing edifices — the pumping stations that supply water to vast swaths of the state.

When operating at full throttle, the Harvey O. Banks Pumping Plant, managed by the state of California, and the U.S. Bureau of Reclamation’s C.W. “Bill” Jones Pumping Plant, have the capacity to entirely reverse the flow on the delta tributaries upon which they sit. The Jones plant alone each year raises 2.5 million acre-feet of water 197 feet to the rim of the delta basin, sending it south via the Delta-Mendota Canal to the farms of the San Joaquin Valley.

Built during the 1940s, these facilities helped spur California’s phenomenal economic success, and now the former deserts of Central and Southern California bloom with more than 300 varieties of commercial crops. But lately, the source of the water these pumps were built to move — snowpack from the Sierra Nevada and Cascade mountain ranges — seems to be shrinking, and that has major implications for agriculture.

A Tumult Over Water
California is in a “state of drought,” something Gov. Arnold Schwarzenegger made official in June when he issued directives calling for “immediate action” on conservation and enhanced supply. (About half of the state’s developed water supply is used directly by people; the balance goes for environmental uses like maintaining wild rivers or endangered species.)

Beyond California’s history of periodic drought, Heather Cooley, of the environmental advocacy-oriented Pacific Institute, said climate change predictions forecast “more severe” and “more frequent” dry spells.

She added that farmers are facing increasing competition for water from expanding cities and industries — and declining species.

A 2007 court ruling restricts pumping on the delta to protect an endangered fish species, the 2-inch-long delta smelt, once the most common fish in the delta but now in such dire shape that the accidental killing in the pumping plans could extinguish the species.

For all of these reasons, Mike Wade, executive director of California Farm Water Coalition, said many Central Valley farmers expect to see their water allocations for the current growing season reduced 30 percent or more. Some have decided to cut their losses and let their fields go fallow.

So while 80 percent of the developed water supply in California is used for agriculture, and despite the impressive infrastructure dedicated to moving farm water around, there are questions surrounding the future of irrigated agriculture in the state.
“We’ve already dammed most of the best sites,” Cooley said. Plus, “expensive new supply projects” are unlikely to make a difference in the short term.

For a long time, Wade said, farmers have been doing the best they can with water already in the pipeline. For example, lining canals — unlined canals can see half the water they transport seep into the ground — and instituting systems that deliver water directly to each plant have reduced some traditional losses.

Charles Burt, chairman of the Irrigation Training and Research Center and professor of irrigation at California Polytechnic State University, San Luis Obispo, believes he can help them do even better — merely by improving the timing and quality of water deliveries to their fields.

A Languid Flow
At the end of the 2005 growing season, and before the beginning of the current drought, the management of the 550,000-acre Central California Irrigation District sought to better coordinate water deliveries to the 600 growers and 4,000 individual farm fields in its west San Joaquin Valley service area. It opted for a major canal modernization project.

At the heart of CCID’s distribution system lie two side-by-side, open-air, gravity-fed canals intersected by feeder troughs running to the various farms served by the district.

The primary channels stretch over 110 miles of terrain so flat that water, released from the regional reservoir at the head of the system, can take two days to reach fields at the end of the system. Jerry Kelley, president of Sierra Controls, a systems integrator involved in the project, said the canals appear so placid they look like “two long skinny lakes.”

In spite of their calm appearance, these canals move a lot of water, and when farmers drawing water from the canals have decided their fields have had their fill, it’s not all that easy to shut off the tap.

“It’s not like at home, where you can just turn the faucet,” Burt said. “The main canal has a flow rate of 600 cubic feet per second — that’s 300,000 gallons per minute.” In comparison, he says a typical showerhead releases two gallons a minute. “Bad things happen when you don’t control the flow. It can go right over the top,” he said

To make matters worse, he added, “If you see a spill at the end of the canal, it’s already too late to do anything about it at the head.”

Barring such a catastrophe, Burt said, for many irrigation system spills have become a routine and accepted business practice. Imprecise control means “sometimes you can be short, sometimes you can be long.” To compensate, he said, growers — who fear crop failure more than the additional expense of surplus water — often order more than they actually need. Any excess is dumped from the canals through controlled spill points into nearby creeks. It’s a waste, both of the water and the energy expended to convey it.

“What these farmers needed was water on demand,” the professor said. But even after eight millennium’s experience of irrigated agriculture, achieving this from a canal network would be like finding a way to “push a string.”

It’s challenging — but not impossible — to push this particular string if, as Burt said, “you play it right” and add “some sophisticated engineering.”

Automation is the key to getting the channels to behave like “a pipeline.” And when it comes to automating very long irrigation canals, Burt said, the irrigation center he helms < http://www.itrc.org/about.htm > is “the only game in town.”

With 14 full-time irrigation specialists on staff, supplemented by 35 students and researchers, Burt said ITRC is managed like a business with “some special expertise that you won’t find at your usual engineering firm.”

In preparation for the CCID modernization project, the irrigation district devised a water plan, mapping out their system and describing the function of each of the canal gates. Using this information, “We developed a scheme to improve their irrigation system to provide better service and conserve water,” Burt said.

A Model of Efficiency
Cutting lag times for deliveries became a top priority. To that end, a new 250-acre-feet auxiliary control reservoir was constructed on 50 acres at the midpoint of the canal, bringing a day’s supply of water to the doorstep of farmers at the farthest end of the system.

In addition, high-tech precision controlled steel gates (including several powered by solar cells) were brought in to replace outmoded wooden flashboard control structures. However, Burt said, the big innovation was in the operation’s nerve center.

The water master plays a critical role in the operation of any irrigation canal system. CCID’s water master, with 14 canal operators under his direction, is responsible for everything from processing orders to directing maintenance on canal structures, all the while supervising crews as they adjust gate settings for water deliveries to customer fields.

According to a consultant on the project, Robert Stoddard of Boyle Engineering, “It’s as much an art as a science,” and the water master’s in-depth knowledge of the local farming practices, crop rotations and the idiosyncrasies of canal topography and hardware is indispensable to successful canal operations.

In order to replicate the water master’s wisdom and experience in an automated system, Burt and his team developed a software model simulating the entire canal, under various conditions, at one-second intervals. By manipulating parameters in the model, Burt said ITRC engineers achieved 90 percent correspondence with the “desired results.” And with “a few heuristic adjustments” to the algorithms to make up the difference, the programming was ready to be entered into control mechanisms.

The control mechanisms were installed in each of the upgraded gates. When activated, they direct each gate to open or close until desired flow rates are achieved.

The control mechanisms maintain constant radio communication with one another and with a central computer in CCID headquarters in the small city of Los Banos, Calif., where the water master can monitor canal operations remotely.

Employees were introduced to the automated system during trial runs in 2007, and at the start of the 2008 growing season, the entire canal network began operating under the new Supervisory Control and Data Acquisition paradigm.

When requests for water reach headquarters from farms beyond the canal’s midpoint, an auxiliary reservoir provides immediate delivery. The gates then act in concert to shunt any overages back into the auxiliary reservoir, eliminating spills and conserving water for future use. The system even integrates billing and administrative functions.

According to Burt, having a consistent and reliable supply of water gives farmers new options for using water-efficient irrigation techniques such as micro-spray or drip irrigation systems.

“In the old days, good service meant just running a lot of extra water down the canal” and that meant a lot of “operational spills.” But SCADA gives “farmers the flexibility they need” to decide exactly how much water they take, and when.

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David Richardson
David Richardson began his journalism career operating a video news service in Washington, D.C., that covered federal agencies and Congress. His film production work has since ranged from postings at the White House to rural villages of Botswana, documenting community-centered HIV prevention programs. He holds a B.A. degree in government from Dartmouth College. He now writes on science, the environment and policy from Baltimore, Md., where he's had some success growing organic produce in a small backyard garden.

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