The region’s current water year is shaping up to be one of the driest on record according to Turlock Irrigation District, with below-average rainfall amplifying California’s existing state of drought.
Data provided by TID hydrologist Olivia Cramer during the Jan. 12 board meeting showed that from September through Jan. 10, the Tuolumne River watershed so far has received 5.55 inches of precipitation. Compared to TID’s historical average of over 19 inches for the same period, the recent rainfall season numbers represent 37.9 percent of normal.
Cramer said weather forecasts in the coming days are bleak and represent less precipitation than predicted by even the driest scenarios. The rivershed could see as little as a quarter of an inch or less than a tenth of an inch of rain in the next weeks based on the forecast.
“Even in our dry scenario, we are expecting at least two more inches from now until the end of January, but based on the 16-day forecast we’re looking at conditions that are even drier than our normally-used dry scenarios,” said Cramer.
Thus far this month, the region has received only a half-inch of rainfall compared to the average of 6.44 inches. Storms brought some relief in December, but only yielded 3.19 inches of precipitation while the average for the month is 5.88 inches. Just 1.82 inches of rain fell in November, which typically sees 4.15 inches, and October and September brought a combined .03 inches of precipitation.
With TID’s dry scenario predictions — which Cramer stated are optimistic given recent forecasts — Don Pedro elevation would sit at about 709.5 feet by the end of the calendar year, and at 792.6 feet should wet conditions unexpectedly arise. In both the dry and average scenarios, reductions in irrigation would need to be made, Cramer said.
“If those forecasts hold and there’s not a shift to wetter conditions, then likely all of the scenarios will shift down slightly due to that lack of precipitation,” she said.
Cramer added that the current water year is comparable to come of the driest years on record. Should forecasts prove accurate, precipitations levels would be close to those of 1977 — the driest year on record. Under average conditions, the water year would more closely resemble 2013. Both 1977 and 2013 were the second years of a prolonged drought, Cramer pointed out, and following a dry 2019-2020 water year, this year is the same.
Cramer stated that the current period from October to January is the second-driest period on record and will likely only become drier. Last year, the region received just 54% of average rainfall numbers for the area. While forecasts could change for the better, they could also change for the worse, she said.
“You always have the possibility of a ‘Miracle March’ or ‘Awesome April,’ but even with extremely wet conditions or fairly wet conditions, we’re really only expecting to get close to average or just slightly below average,” Cramer said. “There’s always a possibility you could have extreme wet conditions even above what’s predicted here, but then you also have the same thing on the dry side.”
The dry conditions have also plagued the state of California as whole this year.
Numbers from the California Department of Water Resources show that the amount of water in the state’s mountain snowpack is only about half of average for early winter, or just 52% of average to date.
According to the U.S. Drought Monitor, 100% of the state is experiencing at least some level of drought, with levels ranging from abnormally dry to moderate, severe, extreme and exceptional drought. Nearly 34 percent of California is in either an extreme or exceptional state of drought. According to the monitor, all of Stanislaus County is currently classified as experiencing severe drought.
While earlier forecasts from last week had previously anticipated more rain and snow than the region actually ended up receiving, Cramer explained that these predictive models are more volatile this year.
“It’s kind of the volatility you would normally see in the fall, and now we’re seeing it within the winter period,” Cramer said, pointing to changes in atmospheric patterns as the culprit. “...Based on that, a lot of these models are changing quickly in order to adapt to those larger atmospheric changes.”
To view the U.S. Drought Monitor, visit https://droughtmonitor.unl.edu.