Water & Resource Conservation

Butte County's Department of Water and Resource Conservation was formed on July 1, 1999 following many years implementing programs to protect the Butte County water resources.

Our Mission: To manage and conserve water and other resources for the citizens of Butte County.

Watch for the Helicopter! Flight to Yield Insights on Aquifer Structure and Materials

 

HelicopterFor a project two years or more in the making, we are excited to be conducting a survey of the aquifer system in portions of the Colusa and proposed Vina subbasins using the Airborne Electromagnetic Method (AEM) beginning Wednesday, November 28, 2018, and lasting several days.  The AEM survey will essentially take an “MRI” of the ground using geophysical methods to collect data to better characterize the stratigraphy and aquifer structure of the groundwater system in a portion of the Northern Sacramento Valley in Butte and Glenn Counties.  This means painting a better picture of the layering and connectivity of sands, gravels, and clays that make up the aquifers of our regional groundwater system. 

How does it work?

Geophysical instruments attached to a low flying helicopter (50-100 feet above the ground surface) towing a large hoop with instruments transmit a weak electromagnetic field.  This field interacts with the ground, and the response from the ground is measured using a set of receiver coils attached to the hoop. The helicopter flies back and forth over a series of regularly spaced lines, similar to mowing a really big lawn. Under some conditions, it can collect data to a depth of about 1,500 feet below ground resulting in 2D slices of detailed variation in electrical resistivity of the subsurface.  Once combined and calibrated with well data and knowledge of the geology, this dataset can be used to map out the layering of “course” (sand and gravel) and “fine” (silts and clay) grained materials that make up the aquifer system. 

This study has been designed to help better understand the structure and vertical connectivity of the aquifer materials and confining beds (i.e. clay layers-How extensive are they?)  and to gain additional insight on the transition from fresh to saline water at depth.  This enhanced scientific understanding of the groundwater system will improve coordination across and between subbasins and perhaps also help guide placement of new monitoring wells or identification of recharge project locations.  The project has two distinct areas as shown in the map. 

SmMap

Larger Map

Western Area

The Western Area includes a region where the transition between the Tuscan and Tehama formation occurs, and coincides with an area where pumping tests determined that some regions of the Lower Tuscan/Tehama system behaves as a confined aquifer system, and other areas where it behaves as a “leaky” or partially confined aquifer system.  Establishing the geometry and nature of the confining aquitard (clay layer(s)) will greatly enhance the ability to model and predictively manage the aquifer system. 

Eastern Area

The Eastern portion of the study area includes a likely recharge region, approaching the eastern edge of the alluvial basin near the foothills.  Understanding the stratigraphy of this area will have a substantial impact on modelling the movement and effect of surface water infiltration on aquifers in the basin.  Basin geometry is poorly understood in this area, and there should be sufficient contrast between basin sediments and bedrock to characterize the shape and structure of the bottom of the basin in this area with AEM.  This area is a transition zone from alluvial to fractured rock groundwater systems. 

Current Status and Next Steps

Data collection by helicopter will begin November 28, 2018, and is expected to take 4-6 days depending on weather conditions.  The total line distance of data collection to be flown is approximately 800 kilo-meters (km) with roughly 3 km spacing between main reconnaissance lines and 500 meters spacing between flight lines in the focus areas in the eastern and western areas.  After data collection, the AEM data will be interpreted in combination with well data, water quality data for total dissolved solids, and knowledge of the basin.  A report describing results is expected in Spring of 2019.

A short clip of the helicopter in action can be viewed here.

Contact Christina Buck with questions. 

    

    

 Contact Water

Water & Resource Conservation
Phone:    530.552.3595
Fax:          530.538.3807
BCWater@ButteCounty.net

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Water & Resource Conservation
308 Nelson Avenue
Oroville, CA 95965

Office Hours
Monday to Friday
8:00am to 5:00pm

Excludes Holidays

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Water Commission Meeting
Wednesday, January 2, 2019, 2:00pm
Board Chambers
25 County Center Dr.
Oroville, CA

Water Commission Meeting
Wednesday, February 6, 2019, 1:30pm
Board Chambers
25 County Center Dr.
Oroville, CA