Not much time for water to soak in before next storms, meteorologist says

The abundance of rain falling over much of California is testing the capacity of Merced County’s water-storage facilities, raising flood concerns and fueling a push for investment in upgrades.

The Merced County Office of Emergency Services warned that flows along the Merced River were certain to increase in coming days as officials released water to make room for more in Lake McClure.

More than 100 people were evacuated from about two dozen homes in Le Grand early Saturday when overflowing Mariposa Creek sent water over streets and into houses, according to county officials.

With above-normal rain totals this winter and strong rates of snowmelt, the capacity of Mariposa Reservoir has been pushed to its limit, county spokesman Mike North said.

The reservoir, which sits about 6 miles northeast of Le Grand and is owned by the U.S. Army Corps of Engineers, overflowed too quickly early Saturday.

The reservoir was designed to hold water and release it slowly, after Mariposa Dam reaches capacity, so the water flows into the Mariposa Creek, he said.

The capacity of the reservoir is 15,500 acre-feet, North said. On Saturday, the level was 15,894 acre-feet.

“A large volume of water in the Mariposa Reservoir resulted in a significant amount of water over the dam spillway,” North said, leading to an overflow downstream.

The dam itself was not compromised, he said.

“The water going over the spillway, (it) is designed to do just that. The Mariposa Dam hasn’t had water flow over the spillway since the 1950s.”

The Army Corps of Engineers, meanwhile, called for increased releases Sunday from New Exchequer Dam east of Snelling.

The releases are needed to make additional space for stormwater in Lake McClure, which the Merced Irrigation District reported was about 90 percent full and continuing to rise.

Emergency personnel have been clearing debris, preparing more sandbags and monitoring local waterways in preparation for the next storms.

While Merced will have a few dry days this week, more rain is expected to arrive Thursday morning, according to Cindy Bean, meteorologist for the National Weather Service in Hanford.

The precipitation is part of a three-storm series expected to last through Feb. 20, she said.

The ground is saturated and can’t hold any more water, Bean said. That could spell more trouble for areas such as Le Grand.

“Hopefully, the ground will be able to dry a little bit. But it’s such a short period. The rain at the end of the week may cause additional problems,” Bean said.

During “back-to-back storms, it’s really hard to recover because there’s no time for the flows to go downstream and the ground to soak it in,” North said.

North added that it could be difficult to reduce the impact and that county workers are doing “all they can” to protect personal property and infrastructure.

U.S. Rep. Jim Costa, D-Fresno, said there has been “more rain and snow than we seem to know what to do with.”

“It’s a destructive force when there’s too much in a little time,” he said.

Building more storage capacity is a long-term fix for the problem, Costa said. In the meantime “all hands are on deck” to make sure everyone impacted by the flooding is being safely evacuated.

This story was originally published February 12, 2017 at 2:48 PM with the headline "Not much time for water to soak in before next storms, meteorologist says."