Theory

1
Theory
Inject electric current into water column with a
dipole and measure electric field at a distance
dipole receiver
2
Theory

• Electric Field Skin Depth for AC signals

Permeability
AC angular frequency
Conductivity
3
Instrumentation
2nd Version- Longitudinal Arrangement
Transmitter
Receivers
-
20 m
6 m
Not to scale
4
Location

• 3 deployments
• Snohomish River in Everett, WA
• Tansy Point in the Columbia River marine estuary
  2008
• Columbia River near Saturn01 2009

SP
Saturn01
5
Inversion Methods
Times of signal change is related to thicknesses
that are roughly high
Correlation between conductivity and salinity
from Saturn01
6
Inversion 2 Fill Method

• Using a dipole model of electric field

P- dipole strength, E- received electric
field r- distance from transmitter to receiver

• - skin depth,
• - conductivity of water within that layer

Rearranging to solve for conductivity
7
Results
Inversion from Sigma Profiler data to salinity
profiles for second deployment
Inversion 1- Cut-off Method
Conductivity time series determined from
calculating threshold from low to high
conductivity values and interpolating to zero.
Inversion 2- Fill Method
Conductivity time series determined by
calculating conductivity values for each time
step and frequency and applying them below the
corresponding
Salinity measured from Saturn01 CTD mooring