In a region spotted with signs that remind residents that “Every Drop Counts,” the news that watershed daily precipitation for July thus far has surpassed the historical average rainfall for the month—although only by a meager 0.02 inches—was still gratefully received.
According to Turlock Irrigation District utility analyst Jason Carkeet, the Tuolumne River Watershed has experienced 0.17 inches of precipitation for July due to the storm that sprinkled the region on July 3. This total comes as 0.02 inches above the historical average of 0.15 inches of precipitation for the entire month of July.
With this total, accumulated precipitation in the Tuolumne River Watershed from September to July 6 now stands at 19.88 inches, or 55 percent of the historical average of 36.25 inches for this date.
Carkeet reported that this rainfall has prompted a spike in runoff of 1,301 cubic feet per second (C.F.S.) in computed natural flow for the Tuolumne River basin, bringing the average C.F.S. for the month to 390 C.F.S. Full natural flow in the Tuolumne River basin stands at 570,125 acre-feet.
“We got just over 1,000 C.F.S. picked up off that storm last week and we exceeded the July average for precipitation,” said Carkeet. “In relative terms, I thought that was good news.”
This is not the first month of the 2015 precipitation year—which spans from September to August—that has exceeded the historical average rainfall amount. During the month of May, the region experienced 1.80 inches of precipitation, a total that exceeded the historical May average by 0.19 inches.
Carkeet reported in May that due to conditions caused by the recent string of dry years, the Tuolumne River Watershed would need at least 42 inches of rainfall over the course of one year in order to get into the range of precipitation that would yield average runoff, which is approximately 1,955,000 acre-feet.
If the region hopes to meet the average amount of precipitation needed to accumulate 1,955,000 acre-feet of runoff, it would need at least another 22.12 inches of rainfall throughout the remainder of July and the entirety of August.
This is amount is nothing short of a miracle to achieve according to Carkeet, who reported in May that precipitation records show no account of precipitation yield for summer months anywhere close to achieving that amount.