Groundwater levels down in Glenn County

Groundwater levels are going down in Glenn County and the Northern Sacramento Valley based on eight-year averages examined in wells by the California Department of Water Resources.

Roy Hull, with the state agency, updated Glenn County Water Advisory Committee members Tuesday on the fall 2011 data, as compared to figures from 2004.

He said the data suggest wells throughout the valley are dropping, but many shallow wells still tested within five feet of normal based on 2004 statistics and their location.

Observation wells are situated in various parts of Glenn County, but include one near the Tehama-Colusa Canal off Highway 32, Hull said. Others are located at different farms in the county.

Additional wells were monitored in Shasta, Tehama and Colusa counties with varied results.

Compared to 2004, the levels are starting to see a steady trend down, he said.

Shallow wells, 200 feet deep or less, are included in the study along with intermediate wells between 200 and 600 feet, and deep wells of 600 feet or more, he said.

The fall study indicates the shallow wells are not that impacted with at least one found to be two feet higher than last year, Hull said. However, one of the deep wells was down 9 feet from the same period in 2010.

Hull added the levels vary depending on the amount of irrigation and pumping being done.

He said 2004 had fairly good rain, but was followed by years with less precipitation, which impacts the water levels.

In 2010, California received a lot of rain and that helped replenish some water supplies, Hull said. However, 2012 is starting off dry so it is difficult to predict how things will turn out by this fall.

Newer observation wells drilled since 2004 were not included in this research since there was no way to do a comparison, he said.

A second report from consultant John Ayres with Brown and Campbell focused on a groundwater recharge feasibility study being done in Glenn County.

Ayres said the study is looking at how to improve information on groundwater levels and the availability of both surface and groundwater in different parts of the county.

It also is looking at land use and the types of crops being grown in this area since orchards generally take groundwater to irrigate while pasture and hay crops may use surface water, he said.

Ayres' data looks at wells drilled between 1950 and 2010 and notes approximately 182 domestic wells were drilled during that time.

They ranged from 10 feet to 1,000 feet deep, but most were 200 feet or less in his study area.

There are 101 irrigation wells listed between 80 feet and 650 feet, he said.

Again, levels fluctuate during irrigation season, Ayres said, and not all Glenn County wells are included in this data.

But the study is only half way done and more input and data is needed to determine whether groundwater recharging is feasible and affordable, he said.

Another public outreach meeting is scheduled for 6:30 p.m., Jan. 25, at Capay Elementary School.

The county is seeking property owners interested in participating in the recharge study and continues to take comments, Ayres said.