Turlock Irrigation District officials remain hopeful that March and April storms will deliver the rain and snow needed to create a normal rainfall season.
The current rainfall shortage is due in part to a very dry start and January seeing a dismal 0.87 inches.
Olivia Cramer, TID’s hydrology analyst, gave a report to the board last week outlining that the watershed had received 8.63 inches of precipitation to date.
“That sets us above average for the month of February but we didn’t quite surpass that wet mark, or the 10 percent exceeded condition for February,” said Cramer, “but overall it helped make up for the lack of precipitation in January.”
As of March 2, 0.59 inches had fallen. That was the day before Wednesday’s boost of rainfall.
More rain is expected this week and Cramer remains optimistic that March and April will bring more precipitation to the watershed.
As of March 2, year-to-date totals for the rainfall season was 19.35 inches. The record was set in 2023 at 30.59 inches . So far rainfall is 76.2 percent of normal as of March 2.
“Moving forward if we have dry conditions, you’re looking at about another four inches and then if you follow up to the average, seven inches and then on the wet conditions about 17 inches.”
She expressed uncertainty about the conflicting 16-day U.S. and European weather prediction models but expects 7 to 10 inches of precipitation.
Cramer said the benefit of last week’s storms is that they were colder and thus the snow at the higher elevation will not immediately begin melting. Ideally a normal spring and summer runoff that feeds into the Tuolumne River helps farmers get the irrigation water needed for crops.
“You won’t see a huge responsive runoff immediately from this storm, which is what we always kind of want to see within the watershed,” Cramer related to the board. “We want to build up that snowpack and get that runoff later through the summer when we have our (water) demands come in.”
As far as the watershed’s snow water equivalent (SWE) is concerned, Cramer said that “right now we are sitting below average.”
More specifically as of the board meeting the snowpack was 68.5 percent of average to date.
The state Department of Water Resources (DWR) routinely surveys the snowpack.
As of Feb. 25, the Tuolumne watershed had an estimated 552,161 acre-feet of snow water equivalent which had been added to since measurements were taken. She estimated about another 160,000 acre-feet in the system in last week’s storms.
An acre-foot of water is the amount it would take to cover one acre 12 inches deep.
Last year the snowpack peaked in April.
“It does depend on if you have some cold spring storms come in. But I think something that is interesting to note is that right now we are, as far as snowpack, sitting very similar to where we were last year at this time.”
Don Pedro Reservoir, the main water storage site from both Turlock and Modesto irrigation districts, held 1,524,598 acre-feet of water and was at the 786 foot elevation.
If the season ends up drier than normal, Cramer said Don Pedro could expect to be drawn down to about the 745-foot mark.
The lake would be about 10 feet below what it was last year if the season finishes at normal levels. A wetter than normal spring, she said, would not only allow the district to meet grower demands for water and fill the reservoir toward its flood control level.
Based on the volatility of the water picture, Wes Miller, director of TID’s Water Distribution Department, the boarded proceeded with an irrigation season to offer between 44 inches to growers with the season to begin March 20 and end Oct. 29. The water call center opens March 19 and will be open weekdays 7 a.m. to 5 p.m. and closed weekends. Releases of water from Turlock Lake will begin March 17.
Growers can order through the online system anytime.
