Groundwater and the Willits Bypass Project

Aerial photo

Aerial photo of Little Lake Valley from Google Maps

On January 29, 2014, an article was published in The Willits News (TWN) written by Linda Williams titled Groundwater in Little Lake Valley. Caltrans would like to expand on some of the facts in this article and relate them to water usage at the Willits Bypass Project. The above article seems to draw much of its information from a California Department of Water Resources (CDWR) document last updated in 2004.

Groundwater reserves in the Little Lake Valley (LLV) have been determined by past state and federal studies to be “substantial and mostly untapped” as TWN article puts it. These studies have estimated the LLV contains from 35,000 to 91,000 acre-feet of water. An acre-foot of water is equal to about 325,851 gallons. Using the most conservative estimate of 35,000 acre-feet means there are at least 11 billion gallons of groundwater available in the LLV. The Willits Bypass Project used about 4 million gallons of groundwater last season, which is about 0.04% of the estimated available groundwater in the LLV.

But what about the water needs of the City of Willits and Brooktrails? Right now neither uses groundwater; they both use surface water from reservoirs. According to TWN article, in 2012 the two water plants produced a total of 1,209 acre-feet of potable water, or about 394 million gallons. Under a worse-case scenario, if both water plants began to use groundwater exclusively they would be consuming less than 4% of the available groundwater each year, or about 100 times what the bypass used last season.

Despite these calculations showing how insignificant Caltrans’ groundwater usage is for our bypass project compared to the amount available, during this unprecedented drought Caltrans will continue to work with the City of Willits to use as much treated waste water as we can throughout the remaining construction.