Lake Mendocino not rising much despite rains

From its stranded boat ramps to the peninsula-like mudflats stretching into what should be the lake, signs at Lake Mendocino suggest the drought is not yet over despite days and days of rain.

As of Wednesday, Lake Mendocino’s water level remained far below normal, in part because of lingering drought conditions and in part because of upstream work that’s keeping water from being diverted into the lake.

“We would need about seven more feet to get to an average water level,” Sonoma County Water Agency spokesman Brad Sherman said. “We’re still in a drought.”

Similar water reservoir conditions persist throughout the state, with some exceptions, like Lake Pillsbury, which reached its water-holding capacity on Wednesday and began spilling over the reservoir’s dam and into the Eel River below.

Normally, that would mean more water than usual could be diverted from the Eel River and down through a mountainside tunnel to PG&E’s power plant, from which it then flows into the Russian River and on to Lake Mendocino. But that’s not happening this winter.

Ongoing repair work to the aging infrastructure of the electricity-generating facility in Potter Valley require that the diversion be kept at minimal flows - about 20 cubic feet per second. Details of the repair project were not immediately available from PG&E Wednesday.

If there were no restrictions, Lake Pillsbury’s overflow could mean a diversion of as much as 10 times that amount, said Janet Pauli, a member of the Potter Valley Irrigation District and Mendocino County Inland Valley Water Commission.

The diversion is important to keeping water in Lake Mendocino and the Russian River later in the year, but not so critical in the winter when it’s raining.

“It’s a tiny portion right now” of the water flowing to the lake, said Mike Dillabough, chief of operations for the U.S. Army Corps of Engineers, San Francisco District.

On Wednesday, water was flowing into Lake Mendocino at rates ranging from a low of ?185 cfs to a high of 1,710 cfs, according to the corps’ website.

Whether the reduction in water flowing through the Potter Valley electric project significantly impacts water available ?in Lake Mendocino later this year depends on whether the storms keep coming.

Since Oct. 1, the Ukiah area has received just over 15 inches of rain, right around average for that time period, according to the National Weather Service.

The most recent rain brought the lake up to nearly 41,000 acre feet, Dillabough said. Its winter capacity is about ?70,000 acre feet. An acre foot is the amount of water it would take to fill an acre one foot deep with water.

“It’s almost getting to the point you can launch a boat,” he said.

A few more feet would allow boat launches to resume, but it will take more than that to alleviate drought conditions.

“It’s been really nice to have nice gentle rains,” Pauli said. “It just has to keep raining.”