The west coast storm that blew into Stanislaus County on Thursday afternoon and into Friday morning dumped approximately two and a half inches of much needed rain, soaking the ground and creating some localized flooding in older Ceres neighborhoods.
Ceres City Manager Toby Wells said city Public Works Department crews were out scrambling with sandbags until 3 a.m. to help keep flood waters from entering some residential garages. He said some areas of the city are not connected to the positive storm drainage system and rely on the rather limited percolation offered by dry wells, which are essentially deep holes filled with larger rocks.
"We weathered the storm pretty well," said Wells. "The winds didn't happen as bad as expected like in other areas."
He said about six trees blew over and were handled by parks crew.
"We had lots of people running around. It was busy."
An estimated 2.2 inches fell in downtown Modesto rain gauges as measured Thursday by Modesto Irrigation District. Another 0.6 inches fell on Friday before noon. More rains came Monday after the weekend was mostly dry.
Don Pedro Reservoir, the principal water storage facility for the area, measured 695.11 feet elevation on Friday at 10 a.m., still very far from its 830-foot maximum lake level. It rose to 695.92 feet by yesterday morning. The recent rains added about 5,000 acre-feet to the lake. MID estimated that Don Pedro had 776,252 acre-feet of water on Tuesday. The lake can hold up to 2.03 million acre-feet.
Turlock Irrigation District utility analyst Jason Carkeet reports that the region is going to need a lot more rain to alleviate the drought. According to Carkeet, what TID considers an "average" year does not depend on the amount of precipitation drops on the Valley floor, rather the deciding factor lies in the amount of accumulated runoff, or precipitation that is either not evaporated or absorbed into the ground.
"What we consider an average year, we put in terms of runoff," reported Carkeet. "The average rainfall we get in the watershed is about 36 inches precipitation, which would give us 1,955,000 acre-feet of runoff from the entire Tuolumne river basin."
Although the region would need 36 inches of rain to get the average amount of runoff, Carkeet revealed that this is not the case following a dry year such as the one the city has been experiencing.
"After a dry year, you're going to need more," said Carkeet. "Following a dry year, some of the water that would otherwise result in immediate runoff goes to recharging the ground and hydrating vegetation."
To achieve the average year's amount of runoff of 1,955,000 acre-feet, the region would need to experience anywhere between 35 to 40 inches of precipitation, which is nearly equivalent to the average amount of rainfall experienced in the watershed throughout the year.
"In order to get the same 1,955,000 acre-feet, we need a whole other year's amount of precipitation, in addition to what we already have to get the average amount of runoff," reported Carkeet.