Tuesday, April 14, 2009 | With a mouse click, a satellite image of an El Cajon restaurant pops up on Jeff Barnes’ computer screen.
The archived image looks like any overhead satellite picture, except that it’s stained red, blotchy from an infrared layer atop it, which shows how much solar radiation bounces off the parcel. Different plants — grass, shrubs, trees — reflect different amounts of infrared. Barnes, a water conservation specialist with the Helix Water District in La Mesa, zooms in and points at a red blob.
“We can see the bulk of the water use is right here, this turf area,” Barnes said, pointing at a blood red patch behind the restaurant. “Over here” — near the street — “is a lighter shade of red. It’s probably shrubs.”
Another mouse click. The restaurant’s water-use history pops up. It has a meter dedicated to measuring its irrigation. Its sprinklers have been spraying an average of 25,000 gallons outdoors each month. A graph reveals that’s way too much for such a small parcel.
A $380,000 program developed by the San Diego County Water Authority and U.S. Bureau of Reclamation tells Barnes how much landscaping the restaurant and every other parcel in the Helix district have, down to the square foot. The program uses an equation to account for the climate zone each parcel sits in and how much water its landscaping demands annually. It then provides an estimate of much water a given property needs to keep its grass green in every two-month billing period — even accounting for seasonal variations.
On average, the restaurant used 25,000 gallons a month. The program estimates that it needed just 6,100. “They’re way over budget,” Barnes said, by 420 percent. voiceofsandiego.org agreed not to identify the specific restaurant in exchange for a behind-the-scenes look at how Helix uses the software.
That restaurant and 877 other Helix customers like it with meters only measuring irrigation will receive notices in the next two months containing that information for their property. It’s called a water budget — a guideline to help people understand not only how much water they use, but how much they should be using.
As San Diego County begins to reconcile its love of lawns with its arid climate and dwindling water supplies, water managers say budgets will grow increasingly common as a way to help residents and business owners understand how much water they should be using outdoors. As much as 60 percent of the region’s potable water is used for irrigation.
“We certainly think water budgets are the direction to head in to help the public understand how much water they’re using,” said Ken Weinberg, water resources director at the San Diego County Water Authority, “and to measure performance and tie it to water rates.”
Starting July 1, Helix plans to require that small group of 878 irrigation users — about 1.5 percent of its customer base — to stick to their budgets. Those who go over will pay rates as much as twice as high as those who stay within their targets.
That narrow user group consumes 747 million gallons annually, or almost 6 percent of the district’s water. It includes single-family homes, parks, schools, CalTrans and commercial buildings. Homes can get irrigation meters to separate their exterior use; other property owners use them to separate what rental tenants may consume inside from shared external use.
Not all of Helix’s customers who will get water budgets are over their allocation. Some use half of what they’ll be allowed. Others, like the restaurant, use far more water than they need.
The imagery and software that makes the budget possible holds promise for the region, potentially putting water budgets a mouse click away. Helix Water District and nine other local water agencies are testing the technology.
But for now, the process of creating budgets is labor intense. Helix needed a year to develop water budgets for its 878 irrigation customers. Two district employees have gone out to every site to double-check the accuracy of the satellite imagery.
Mark Weston, Helix’s general manager, said the district has no immediate plans to implement budgets for all of its 55,000 accounts. “It is something we’re going to have to watch,” he said.
The program’s kinks would first need to be ironed out. For example, some landscaping can be obscured by roof overhangs. “You find a lot of little nuances when you visit the sites,” Barnes said.
Mayda Portillo, senior water resources specialist at the water authority, the region’s water wholesaler, said neighborhoods managed by homeowners associations can also pose challenges, where slivers of common space wind throughout. “You can’t just apply a broad stroke,” she said.
The technology demonstrates one possible path the city of San Diego could take if it chose to create water budgets for its 270,000 customer accounts. The city has used the software and has access to it, though it’s not the only method for creating a budget.
The Irvine Ranch Water District, which serves 91,000 customer accounts in Orange County, didn’t use the technology in 1991 when it created water budgets. Today, the district uses a combination of mapping software and estimates of each parcel’s landscaped area.
San Diego water officials have rejected water budgets as being an impractical way to cut demand in the short-term, though they have misrepresented how Irvine Ranch implemented its plan.
The infrared technology has other applications, helping water agencies pinpoint inefficient irrigation. The imagery can reveal where sprinklers are over-spraying or under-spraying on a large parcel.
“Football fields, I love,” Helix’s Barnes said, and zoomed in on a local pitch. The field looked a fiery red; a dark magenta streak stretched from the 50-yard line toward each end zone.
“It’s always the center of the field that’s weak,” he said. “When you turn on the infrared, it’s night and day.”
Please contact Rob Davis directly at rob.davis@voiceofsandiego.org with your thoughts, ideas, personal stories or tips. Or set the tone of the debate with a letter to the editor.