Local growers serviced by the Turlock Irrigation District will see a 34-inch water cap allotment this irrigation season, set to begin March 18.
The water cap is a decrease from last year’s 42-inch allotment and comes as the Tuolumne River Watershed experiences what has been a historically-dry water year — and a second consecutive year of below-average rainfall. Under a resolution approved by the TID Board of Directors on Tuesday, the 2021 irrigation season will last 223 days and run through Oct. 27.
TID Hydrology Utility Analyst Olivia Cramer provided information on how much precipitation has fallen this water year, which began in September. To date, 14.27 inches of rainfall, or about 54% percent of the historical average for the date, has accumulated in the watershed.
TID staff isn’t expecting much more moving forward; with the exception of a slim possibility for atmospheric rivers to occur between now and the end of May, there are likely to be no large precipitation events for the rest of the water year, Cramer explained. Even if there were, wet conditions in the months to come still wouldn’t put the water year at the historical average.
To determine how much water should be allotted to farmers this year, TID examined the most recent drought on record, which began in 2012 and lasted through 2016. In 2012, the Tuolumne River Watershed received 48% of the historical average in rainfall and growers were allotted 40 inches. In 2020, the irrigation cap was set at 42 inches following a 51% water year.
In order to decide how much irrigation water should be provided this season, TID looked at the 2013 allotment, which was also a second consecutive dry year like the region is currently experiencing. Since the current water year could end up with even less precipitation than the 2013 value of 59%, TID decided to mimic that year’s water cap of 34 inches.
The Tuolumne River Watershed was expected to receive .32 inches of rainfall on Tuesday and another .22 inches on Wednesday, as well as an additional .04 inches through March 17, the day before the irrigation season is set to begin.
TID Water Distribution Department Manager Mike Kavarian stated that should the area receive anywhere from an inch to an inch and a half of rainfall before the season begins, irrigation could be pushed back another week.
“We have had very few people ask us as far as irrigation. We’re getting people irrigating right now, but there’s no crisis right now,” Kavarian said. “If we get an inch, an inch and a half, we can push it back, but other than that we’ll look to see where we’re at right now.”
The 34-inch water cap is lower than last year’s, but ample compared to years past during drought conditions. In 2014, the allotment dropped from 34 inches the year prior to just 20 inches. The next year, 2015, saw TID implement a historically-low water cap of 18 inches. By 2016, however, that number was doubled and the allotment was set at 36 inches.