Flow meters assume added importance on farms

As more scrutiny is applied to agricultural water use, the flow meter is emerging as one of the most important pieces of equipment on many farms.

Flow meters come in various shapes and sizes and with various price tags, but they all have the same function: to measure the rate at which water is sent from the pump to orchards or other crops.

The devices can help growers comply with Senate Bill 88, which requires those who divert 10 acre-feet of water or more per year from rivers and streams to measure and report the diversions, noted Allan Fulton, a University of California Cooperative Extension irrigation and water resources advisor based in Red Bluff. All diversions must be reported annually, with the measurement requirement applied to diversions of 10 acre-feet or more.

UCCE experts are developing a course that will certify landowners to install their own water-measuring devices. A law that took effect Jan. 1 authorizes those who divert more than 100 acre-feet of water a year to certify their water measuring devices are installed and operating properly if they take such a course from UCCE; diversions of fewer than 100 acre-feet may be certified by an individual experienced with measurement and monitoring. The UC courses will likely kick off in February, Fulton said.

But government mandates aside, Fulton said, a good flow meter can also give a grower more specific information when seeking advice about irrigation management and help troubleshoot problems.

"Better information makes for more confidence in your opinions and decisions," he said.

Water districts have been using flow meters since the 1960s and early 1970s to meet their own reporting requirements, Fulton said. The meters then were mostly impellers—propeller-like devices put inside the line that spin as water passes through. That can present a problem if weeds and other debris become tangled in the blades, he said.

Although impellers remain in use, many meters today use sound waves or magnetic fields to measure flow, Fulton said, and some metering systems use telemetry to enable a grower to see and compare measurements with a computer or cell phone off-site.

"I think there are more manual flow meters (in use) now than automated," Fulton said.

Depending on their size and complexity, most flow meters range in cost from as low as $500 to more than $1,500, he said. They're usually installed at each pump and measure the average water applied per acre. In addition, growers can put smaller meters costing $50 to $100 on the lines to make sure applications are uniform.

The meter's location matters, Fulton said, advising that it's best to put it in the middle of a straight pipeline where flow is going uphill or at least laterally.

"The pipe has to be full, so we're trying to avoid turbulent flow," he said.

The meter can help a grower identify pump wear and tear, recognize when the groundwater table is receding and know if there are flaws in the system, he said.

"The flow meter is a management tool," Fulton said. "It's a source of information that can help us in decisions of when to irrigate and how much water to apply."

Jarald Davidson, owner of the Chico-based business Irrigate.net, said he received more calls about meters as SB 88 deadlines loomed. Water right holders diverting between 10 and 100 acre-feet per year had until Jan. 1 to install measurement devices or submit alternative plans to comply.

Davidson started his business in 1981, offering detailed soil moisture analysis, and now his company focuses mainly on monitoring pumping plants for flows and using telemetry and data logging to keep track of the information, he said.

Irrigate.net sells higher-end McCrometer systems that can start at about $1,000 but commonly sell in the $2,000 to $3,000 range, Davidson said. One system, designed for conditions where there isn't enough straight pipe to use a standard meter, sells for as much as $6,000, he said. Davidson opted to sell higher-end systems because he said others may not be certifiable for correct flows.

In addition to diverters, Davidson said other demand for flow meters has come from orchardists taking part in government programs that require such monitoring. There's interest among those who use drip irrigation in having the meters for management, he said.

"If you monitor it correctly, you'll know if the emitters are starting to plug up or if there's a major break in the system," Davidson said. "We have sensors ahead of the filter and after the filter, so if the filter plugs up, we'll know."

Davidson said he expects to sell more meters as local entities begin to impose groundwater regulations.

"I think the way the groundwater sustainability act is worded, there will be some reporting requirement of every groundwater pumper," he said.

Under the current rules, growers don't necessarily need a flow meter. They can track the energy going into the pumping unit and calculate the amount of acre-feet per unit of energy produced to give an account of how much water was diverted, Davidson said.

Orchardists simply keeping tabs on water delivery have different means of doing so, Fulton said. For instance, they can use catch cans to measure water coming out of the nozzles or sprinkler heads at various locations, but he said those measures may not be as accurate.

"The key point is that, depending on which alternative you use, there can be a range of about 20 percent variance," Fulton said. "It raises the question of whether you can make improvements."

(Tim Hearden is a reporter in Redding. He may be contacted at timhearden@gmail.com.)