Rains bring respite for the Sonoma Valley environment

Recent rains have triggered a host of problems in Sonoma Valley, including hazardous driving and flooding, but they have also brought a welcome respite for the environment.

“Nature seems very happy with the rains, and the recent rains especially,” said Richard Dale, executive director of Sonoma Ecology Center. “Pools are forming, amphibians are coming out of their hiding places, all the annual plants are starting to sprout and mosses are greening up. It’s really springtime for much of nature in California.”

So, there are plenty of reasons to welcome the rains — if they aren’t excessive.

“If the rains are constant but the rain comes slowly or moderately, we likely we won’t see many issues,” Dale said. “Fortunately, so far much of this rain is making its way into the ground. If we get more storms like the one on Monday night, we’ll see more flooding and erosion.”

Prior to the recent storms, California had received only about 50% of normal rainfall for the season, though every year the state has a lot of variation. In Sonoma, the storm early this week added nearly 3.5 inches of rain, moving the city’s rainfall to 85% of normal. Storms through New Year’s Eve were forecast to bring about another 3 inches, which would put Sonoma above average rainfall for the season and make December well above average.

Dale says that there are two main problems associated with reduced rainfall.

“One affects nature, and is often referred to as a landscape drought,” he said. “We are several years into this kind of dry period, and combined with a warming climate, which increases evaporation in soil and transpiration in plants, a lot of woody plants become severely stressed. You can see this on hillsides around Sonoma, with tree mortality increasing. This is also stressful to wildlife because almost all animals rely on surface water for survival and many to reproduce.

“The other kind of drought is more directly felt by people, as groundwater and surface water used at home and work are affected and water levels drop, sometimes precariously.”

He noted that Lake Sonoma and Lake Mendocino, both of which are reservoirs that feed the Russian River — and in turn, serve thousands of North Bay residents — are low, with Lake Sonoma still only at 40% capacity after the rain on Monday, Dec. 26.

Caitlin Cornwall, senior project manager for Sonoma Ecology Center, says that climate change is impacting the rains. Major flooding can occur when a big storm coincides with a high tide, as was the case in late December 2005, when weekend flooding on the north coast affected 34 California counties, including Sonoma, causing an estimated $300 million in damage.

Jessica Misuraca, chair of the Sonoma Overlook Trail Stewards, says the lack of rain has had an effect on the ecosystem at large, with a trickle-down effect on the wildlife.

“Less rain equals less plant life, equals less fuel for wildlife,” she said. “Less water in our local tributaries means that deer and other creatures need to follow the creeks further into town during the dry season.”

She says that after a long, dry year followed by significant rainfall, many trees at Sonoma Overlook Trail and Montini Open Space Preserve break off at the trunk as they are dehydrated and weak, and all the water they then absorb makes them too heavy for the trunk to support.

“Dehydrated trees are also more susceptible to other stressors, such as insect and microorganism predation, and their bark becomes less protective,” Misuraca said.

Sonoma Ecology Center has worked for many years to educate the Sonoma Valley community about the value of capturing rain water during the wet season.

“A great adage about water in California, created by our colleague, Brock Dolman of Occidental Arts & Ecology Center, is ‘slow it, spread it, sink it.’” Dale said. “We often have parts of the wet season like we did Tuesday with a lot of water in Sonoma, but because it is moved more quickly off the land to favor our homes and fields, it doesn’t get into the ground where it will help supply streams and homes in the dry season. Doing this also helps reduce the impacts of flooding.”

Sonoma Ecology Center shares this concept in the community through projects such as the rainwater capture demonstration garden at Sonoma Garden Park, the rainwater capture efforts at Flowery Elementary School and the restoration of streams around the Valley, as well as helping landowners and managers reduce fire fuels on their property.

“The way this work done can move water off the land more quickly or it can help it into the ground, and help maintain or improve biodiversity on the land,” Dale said.

He says that in collaboration with the city of Sonoma, Sonoma Water does an “excellent” job of staying on top of stormwater issues in Sonoma and the Valley, adding that Sonoma Ecology Center helps Sonoma Water with some debris removal.

“We are working together longer term on large projects to try to ‘slow, spread and sink’ rainwater in the upper parts of our watershed so that there will be more water retained here and less flooding,” Dale said.

Reach the reporter, Dan Johnson, at daniel.johnson@sonomanews.com.