Forecasting water deliveries complicated by unknowns

Forecasting water deliveries complicated by unknowns

Forecasting California water deliveries is complicated by two factors: Regulatory uncertainty when it comes to protection of the environment and hydrologic uncertainty as to just how much snow and rain will fall.

One of the driest calendar years in California history dampened the mood at this year’s drought preparedness workshop at Fresno State University, where participants talked of what could be record low allocations of water through the Central Valley Water Project.

Speakers this year were more outspoken than they were at last year’s preparedness workshop, perhaps because that one came during a wet December, compared to this year’s event, which was held in the middle of a dry month with little or no precipitation in sight before year’s end.

At the same time, they cautioned that the dry picture could change with just a few storms. “We need to prepare for the worst and hope for the best,” said Jeanine Jones, interstate resources manager with the California Department of Water Resources.

Speakers urged those thinking of contracting for water transfers to do so sooner rather than later. They talked of a lowering groundwater table and the need to be sure pumps will be ready and up to the task of lifting water so it can be used on crops.

Bill Green, an authority on pumping efficiency with Fresno State’s Center for Irrigation Technology, he is looking at making some changes with a pump on his farm where he grows raisin grapes because of a loss in efficiency.

“Maybe we’ll get lucky,” he said, “and from now to the end of the season we’ll get 20 inches of rain and 40 inches of snow in the mountains and the water levels will come up and everything will be perfect. But I’m not going to bank on that. I’m going to pull my pump and get it fixed.

“This is serious stuff. This drought is serious. Don’t wait until next April when you have to irrigate.”


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The state is facing a third consecutive dry year unless the picture changes dramatically in the months ahead.

Another dry year would mean that seven of the last eight fall into the categories of “below normal, dry or critically dry,” said John Leahigh, with the State Water Project Operations Control Office.

Leahigh talked of what could be the lowest allocation ever for project deliveries south of the Delta, now set at just 5 percent. Initial allocations have often been increased as the water year unfolds, but last year an allocation of 30 percent was raised to 40 percent and then rolled back to 35 percent.

Forecasting what deliveries will amount to is complicated by two factors, Leahigh said: Regulatory uncertainty when it comes to protection of the environment and endangered species and hydrologic uncertainty as to just how much snow and rain will fall. “A couple of storms can make the difference between a dry year and a wet year,” he said.

Leahigh showed a chart with rainfall levels for the Northern Sierra that this year “mimics the driest year on record (1923-24).”

“To get back to average, we would need something wetter than the top 10 wet years,” he said. “That tells you the kind of hole we’re in.”

On the same day the workshop was held, Westlands Water District issued a press release saying the Valley faces “an historic low point in water supply reliability,” and that that region alone, encompassing parts of western Fresno and Kings Counties, could see a potential economic impact that could exceed $1 billion.

Measure to manage

Leahigh also talked of “a ridiculously dry scenario for the Southern Sierra,” and pointed to low stocks of stored water: 38 percent of total capacity in Lake Oroville and 23 percent in the San Luis Reservoir.

Jones said any long term outlook for the state “doesn’t have the word wet sprinkled throughout it.”

She said the greatest impacts of the dry spell have been on range land and forests where wildfires have raged. She said other drought impacts can be expected on small water systems in rural areas.

Groundwater levels have dropped, and the state is keeping an eye of subsidence that has resulted in the northern part of the Valley.

Reliance on groundwater is particularly high in the Central Valley, said Dave Mathis, senior engineering geologist with the Division of Integrated Regional Water Management. Groundwater accounts for between 30 percent to 40 percent of the state’s water supply.


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Tom Filler, with DWR’s Water Transfer Program, said water transfers “have become a way of life” since 1995. He said his staff was heavily burdened by proposals for transfers that were filed late. “Act early on” was his advice for this year. Proposals can be submitted to the U.S. Bureau of Reclamation or DWR.

Val Dolcini, state executive director of the U.S. Department of Agriculture’s Farm Service Agency, talked of loans with interest as low as 1.875 percent that can help provide some assistance to those facing challenges from the drought’s impact on crop losses, livestock losses or damage on ranches because of wildfires.

Rob Roy, with the Natural Resources Conservation Service, talked of federal assistance that could be made available through such activities as the Environmental Quality Incentives Program.

Roy said some funding is also available to regional industry groups through the Agricultural Water Enhancement Program. Among those who have used that program is Western United Dairymen based in Modesto.

Blake Sanden, University of California irrigation and agronomy farm advisor in Kern County, talked of the toll that deficit irrigation can take on crop yield, and said purchasing additional water may pay off if that difference in yield proves too costly.

“Check out your dirt,” he said, stressing the importance of monitoring soil moisture and irrigation impacts. Showing one slide, he suggested first getting on your knees to pray and then getting on your knees to “check the soil profile, emitter flow rates, adjust pressure regulators and optimize uniformity.”

Kaomine Vang, project manager at the Center for Irrigation Technology, talked of a software tool that can help in irrigation scheduling. Information on that is available at Using the software can result in savings of energy and money, he said.

“You have to measure water to manage water,” said Vang’s colleague, Green. He said a flow meter proved invaluable in letting him know of a flaw with his pump. He blamed a drop in flow rates on deeper groundwater.

Green recommends having pumps tested periodically, checking for plugged emitters, making sure pressure gauges are functioning properly, and properly maintaining the irrigation system to achieve distribution uniformity.


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