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TID to consider additional irrigation water

POSTED April 10, 2012 9:44 p.m.

Turlock Irrigation District directors may increase the available irrigation water this year, thanks to better than expected rainfall – and a potential windfall of water from the City and County of San Francisco.

On Tuesday, directors will consider upping the irrigation cap from 30 acre-inches to 36 acre-inches this year, while holding the allotment steady at 24 acre-inches.

“It’s hard not to increase the allotment when you look east and see all that snow in the mountains,” said TID Director Rob Santos.

The extra precipitation amounts to about 30,000 acre-feet of unexpected water – a sizable amount, but not enough to significantly change TID’s forecast curves. But a further 80,000 acre-feet could be released to TID’s Don Pedro Reservoir from CCSF’s Cherry Reservoir, as San Francisco must perform needed maintenance on submerged pumps.

Without the San Francisco releases, TID would carry over enough water to deliver 20 acre-inches to farmers in 2013, should no precipitation fall in the coming year. But with the extra 80,000 acre-feet of water, those carryover reserves would rise to 24 acre-inches.

The plan to offer additional irrigation water would essentially make available to farmers the extra precipitation runoff, while carrying over all of the San Francisco diversions. Without those diversions, TID would be inclined to retain the extra runoff as carryover storage.

Directors at Tuesday’s TID board meeting supported the plan, but Board President Michael Frantz emphasized caution. San Francisco originally planned to release water from Cherry Reservoir in 2011, but changed plans at the last minute – after TID released water from Don Pedro Reservoir to make room for the anticipated diversions.

“I'm not opposed to anything you're saying, but I hate to rely on the kindness of strangers for our long-term planning,” Frantz said.

Even if the San Francisco transfers don’t come through, raising this year’s cap makes sense to Director Ron Macedo. The extra water would allow farmers to save their investment in this year’s crops, and plan ahead for a 2013 with a smaller allocation, he said.

And Director Charles Fernandes opted to look on the brighter side, noting that should the 2013 water year be as rainy as 2011, Don Pedro Reservoir could be filled to the brim, with more water coming down the Tuolumne River than the reservoir can hold.

“I don’t want to get in a situation where we’re so conservative we’re holding water from the growers, then next year we have a wet year and we’re spilling water,” Fernandes said.

TID planners are a bit more conservative, though, looking ahead six years when suggesting irrigation water allocations.

With just average precipitation, Don Pedro would take two years of rainfall to fill after this dry year, said TID analyst Jason Carkeet. But should dry conditions continue, it could take six years to refill Don Pedro –potentially with irrigation allotments of 30 acre-inches or less.

 It all comes down to precipitation, Carkeet said.

“That’s what we don’t know,” Carkeet said. “That’s the question.”

While no one can predict rainfall in future years, recent, unexpected showers have been a boon to the beginning of irrigation season.

Growers clamored for water at the March 8 start of irrigation season, with almost 40 percent of total season orders placed on day one. But the consistent rainfall has driven irrigation water deliveries well below projections, said TID Water Distribution Department Manager Mike Kavarian.

“This rain every week or 10 days is really working for us,” Kavarian said.

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