The Turlock Irrigation District on Tuesday put a cap on water deliveries to farmers, a measure it last used during the 1987-92 drought.
The Modesto Irrigation District, which shares Don Pedro Reservoir with the TID, does not have a cap but is watching the 2008 supply closely.
And Stanislaus County's largest domestic water systems, run by the cities of Modesto and Turlock, expect to get through the year OK if customers follow the outdoor watering rules. That could start to be tested Friday, when the temperature is forecast to top 80 degrees.
The TID board voted unanimously to cap water use at 3.5 acre-feet per acre during the 2008 irrigation season, which started last month. An acre-foot is enough to cover an acre to a depth of 1 foot.
The move was prompted by concern that the just-ended winter was the second in a row with below-average rain and snow. TID officials said they want to save some of this year's supply in Don Pedro in case next year also is dry.
Usually, farmers are free to use as much water as they want, as long as they pay the increased prices charged for higher volume per acre. This year, TID will have a firm cap.
"It's going to create a hardship for some people," said Wendel Trinkler Jr., a dairy farmer in the Ceres area.
He said he has used part of his 2008 allotment to grow a spring feed crop and faces the prospect of planting a summer crop with much less water.
The cap will affect 23 percent of the TID's acreage, the staff estimated. Some of the district's 5,800 customers can get by with less because of the water needs of their crops or their access to groundwater.
The board also voted to end the irrigation season Oct. 7, a week earlier than usual.
The cap could be revisited if water conditions improve, district spokeswoman Michelle Rei- mers said.
The board set this year's base allotment -- the amount of water available for the flat fee of $20 per acre -- at 2½ acre-feet. Farmers can get another acre-foot, putting them at the cap, for $10.
The MID's base allotment is 3 feet this year, available at $23.50 per acre. The charge is $11.75 per acre for each foot after that, up to 6 feet, then $20 per acre.
MID Director Cecil Hensley suggested raising the base allotment to 42 inches. He said much of the increased water would seep underground, bolstering the aquifer tapped by the city of Modesto.
The board agreed to revisit the allotment in a couple of months and possibly tweak it to reflect summer conditions.
The Tuolumne River is projected to flow at 83 percent of its average volume this year, said Walt Ward, assistant general manager of water operations at the MID. The very wet January was canceled by the bone-dry March, he said.
The city of Modesto uses a combination of surface water from the Tuolumne and groundwater. This system also supplies Empire, Salida, Waterford, Hickman, Grayson, Del Rio and small parts of Ceres and Turlock.
Despite the dry weather in recent weeks, consumption has not been heavy, said Allen Lagarbo, acting public works director for Modesto. He said that could be because many days, although dry, have been so cool and cloudy that people do not feel a need to water.
The Modesto odd-even system allows each resident to water only three days a week, and never from noon to 7 p.m.
"We haven't seen a big increase," Lagarbo said. "I think our customers are really responding well."
The city of Turlock has roughly similar water rules and a groundwater-only supply. It looks to be adequate for the year, thanks to a slowdown in population growth and the availability of many wells, said Michael Cooke, regulatory affairs manager for the city.
"It usually takes a couple of years for a lack of rain to show up in the aquifer," he said.
Bee staff writer John Holland can be reached at email@example.com or 578-2385.