Siskiyou County Supervisor District 5, Marcia Armstrong
Pioneer Press - December 2, 2005
There has been growing pressure to better understand the Scott River’s
groundwater table and how it is recharged. A few weeks ago, Mark Horney and
Bill Waggoner of the Natural Resource Conservation Service (NRCS) Watershed
Team presented a modest proposal for a voluntary groundwater monitoring
program. The strategy protects individual privacy, but would produce
information of use to landowners as their management tool. It is estimated
that such a study could be accomplished without public funds for a minimal
amount of money.
In his presentation, Horney indicated that there the aquifer exists below soil
deposits that can range from a few feet to several hundred feet in depth.
Horney said that it is simplistic to think of the aquifer as a ridge to ridge
bathtub holding sediment and water. The depth of bedrock – the rock layer
through which water cannot pass, can vary from a few feet in Callahan to
several hundred feet in the lower valley. There are also various densities of
soil type. For instance, water can pass through gravelly soil quickly, while
clay layers are hard to pass through. There may even be underground rock
ridges that serve as a barrier to water movement.
In the 1940s and 50s, Seymour Mack surveyed the characteristics of the aquifer
by monitoring 105 wells. He determined that there were 8-9 different geologic
formations in Scott Valley that have contributed to the sedimentary mix in
different areas and the rate of recharge. There are nine different drainages.
To add more complexity, there are also ancient riverbeds beneath the surface
that have filled with sediment.
Horney stated that several factors influence how fast groundwater will move:
(1) The type of soil material through which it passes; (2) The gradient or
slope; (3) The porosity of the material (amount of space between particles);
and (4) The permeability (connection of those spaces.)
According to Bill Waggoner, groundwater is particularly important to Scott
Valley. Nationally, about 50% of domestic water supplies are from groundwater.
In the Scott, it is closer to 90%. Summer accretion of groundwater is also
important to summer river flows. Monitoring a grid of about 30 wells on a
purely voluntary basis on the Scott Valley floor could produce useful baseline
data to answer questions for each local area such as: (1) The relationship of
groundwater storage to discharge and recharge; (2) The evidence of multiple
aquifer strata or layers; (3) Seasonal variation in groundwater levels; and
(4) Long-term trends in groundwater levels. The wells could be existing
irrigation wells that are not currently in production (not-pumping for at
least three days.) Waggoner stated that it will take at least a decade or two
to capture a true picture of groundwater for each area.
For more information, please contact the Scott River Watershed Council at
468-2487.