About two decades ago, the Turlock Irrigation District started using electronic flow meters. They could be off by as much as a fifth, but they still helped with the imperfect science of delivering water in open canals.
That won’t cut it anymore. A state law requires greater accuracy for irrigation districts by the end of next year, with the goal of stretching a resource vital to farms, cities and fish.
The TID has started to fit its canal gates – the openings that let water into fields and orchards – with higher-tech devices that constantly measure the flow. The old system took just one measurement during irrigation.
“We were off by possibly 20 percent in the past,” said Wes Miller, supervising engineering technician for the district. The new system “will tell us exactly what went through the gate and what we delivered.”
The law, part of the Water Conservation Act of 2009, allows a margin of error of up to 12 percent for existing meters. New or replacement devices can be up to 5 percent off if certified by a laboratory or 10 percent if certified elsewhere. Miller said the TID’s new meters tested at being off by just 2.5 percent.
The TID plans to spend about $10.9 million on its makeover. The Modesto Irrigation District, its partner on the Tuolumne River, has budgeted $100,000 this year to study various technologies, spokeswoman Melissa Williams said; the total cost is not known.
The Oakdale Irrigation District on the Stanislaus River could have an estimate of its cost in September, General Manager Steve Knell said. He warned that it will be substantial for the OID, which long has charged a flat rate for water deliveries to farmers rather than by volume.
Miller talked about the effort during a recent visit to the Turlock Main Canal, just south of Denair. It is one of many channels serving about 149,000 acres in the TID, the largest irrigation district in the Northern San Joaquin Valley.
The TID purchased its new meters from Rubicon Water, an Australian-based company with a branch in Modesto. About half of its acreage will be served by devices that remain on the gates. Much of the other land will be served by portable meters, moved from gate to gate during the season. Other meters are planned for farmers who pump canal water.
Each gate meter uses 32 ultrasonic beams to measure the water going through the opening, Miller said. The installation also has a control box where a farmer or TID ditchtender with a password can select the flow rate and open the gate to the desired vertical inches. It can be operated by smartphone or other remote means.
Miller said the new system could mean more income for the TID, if it shows that some farmers have been getting more water than they were billed for. “There’s going to be a lot of water found because of this,” he said.
Knell said about 65 percent of the OID’s gates meet the new standards, but getting the rest there could cost plenty. The district is looking at a possible rate increase for 2015 that would include this work.
“This is a regulatory requirement and its costs will unfortunately be paid for by water users within irrigation districts,” he said.
Bee staff writer John Holland can be reached at email@example.com or (209) 578-2385.