GPS

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Mobile Conductivity Assessment System (MCA) used
for canal seepage surveys
GPS
EM-31
On-board LAPTOP
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Canal survey (Losthills)
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EM-31
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(No Transcript)
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(No Transcript)
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Canal surveys

• Study location Lost Hills Water District, Kern
  County, CA. (Unlined section area 5 North ditch,
  about 3,700 ft long).
• Study period August 2001 when canal was open.
• Canal surveys A Mobile Conductivity Assessment
  (MCA) System was developed that comprised four
  components mounted on a truck (1) an
  electromagnetic induction sensor EM-31, (2) a
  global positioning system (GPS) receiver, (3) a
  computer, and (4) a hydraulic soil sampler (Fig.
  1). The EM sensor was placed in a plastic
  carrier-sledge attached to the rear of the truck
  and measured the depth-weighted apparent soil EC
  down to 10 ft. The EM and GPS instruments were
  connected via digital interfaces to an on-board
  laptop computer that simultaneously recorded the
  EM readings and their corresponding GPS locations
  using a Salinity surveyor software (US
  Positioning, NM).

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Canal surveys (cont.)

• Electromagnetic induction principle the EM
  transmitter coil induces an electromagnetic field
  in the ground, which in turn creates a secondary
  magnetic field that is measured by the receiver
  coil. The ratio of both fields provides a
  measure of the depth-weighted apparent electrical
  conductivity (EC) in a volume of soil below both
  coils. Since EC of a soil is a function of its
  water content, salt content, texture, use of the
  EM technique can be very valuable for canal
  seepage assessment.
• Data calibration and analyses using ESAP-95
  statistical package following ground-truthing
  soil sampling (0-8 ft). Soils were analyzed for
  EC, bulk density, water content, and texture.
• Output data Contour maps of soil EC and water
  content, and clay content using ArcView GIS.

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Mobile Conductivity Assessment System
(MCA) used for salinity surveys
GPS
Laptop
EM-38 placed in a plastic sled
Hydraulic soil sampler
Spray Coupe
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Geonics EM-38 Dual Dipole Conductivity Meter
Unit in vertical dipole mode
Unit in horizontal dipole mode
Serial RS232 digital interface to connect EM
meter and computer
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Salinity distribution 0-1 ft (1st field)
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Salinity distribution 0-1 ft (2nd field)