Great Salt Lake Bathymetry Purpose, Process, and Results

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Great Salt LakeBathymetryPurpose, Process, and
Results
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Great Salt Lake Bathymetry

• Background
• The largest U.S. lake west of the Mississippi
  River
• The 4th largest terminal lake (no outlet) in the
  world
• About 75 miles long, and 28 miles wide, and
  covers 1,700 square miles
• One of the largest migratory bird magnets in
  Western North America
• Actually very little known about the lake until
  recently (still a long way to go)

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Great Salt Lake Bathymetry

• Purpose
• Define shape of basin(s)
• Lake circulation models / Movement of
  constituents
• Shoreline inundation / Habitat definition
• Explanation of observed phenomena (Saline layer)
• Tectonic history / fault locations
• Define area/volume/elevation relation
• Salt balance calculations / Mineral resources
• Implications for ecological modeling/brine shrimp
• Occurrence/distribution of benthic habitats, food
  supplies, etc.
• Water budgets / meteorological applications
• One of the major unknowns about the lake

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Great Salt Lake Today
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Great Salt Lake Bathymetry
Work divided into two efforts primarily because
of funding issues. Cooperative effort between
USGS and DWildlifeR South State Lands - North
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Great Salt Lake Bathymetry

• Physical Parameters of the lake/water
• High density brine (9-26 percent NaCl)
• High sound velocities
• High coefficient of friction
• Electrically conductive
• Shallow Water
• Access limitations
• Short timing intervals
• Surfs up/Windy!!!

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Great Salt Lake Bathymetry

• Equipment Issues
• Equipment not designed for GSL Conditions
• Shallow/high speed depths
• High density water (physical issues)
• Speed of sound corrections
• CTD solution not available (Cond/Temp/Depth)
• Oceanographic equipment too slow
• Marine engines near saturation NaCl water

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After one day
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Great Salt Lake Bathymetry

• Equipment Solutions
• Navigation Commercial package
• Depth
• Very Narrow Beam, High Resolution Transducer
• 2.8 degree single beam, 200KHz
• Position
• RTDGPS
• lt1m Real-time
• Industrial SVS (this was the secret)
• Ruggedized everything
• Electrical/hardware/mounting brackets/etc. (kiss)
• Great mechanic/modified engines

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Great Salt Lake Bathymetry

• Acquisition parameters
• Generally less than 6 inches of chop
• Depends on direction/effect on data
• No observable swell on paper record
• Depth greater than 0.7 meters
• Safety
• Timing problems (multiples)
• No rain/heavy precipitation
• Generator / 112V AC
• SVS profiles (intermittent)

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Quality control Vertical acquisition (adjustabl
e angle) High data rate Multiple sv
profiles Digital analog Set transducer
depth Nightly backup DGPS feedback loop RTDGPS
submeter
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Great Salt Lake North Bathymetry

• Results
• 12.8 million total
• X-Y-Z points
• 5.2 million points
• 765 miles
• 1,230 kilometers
• 240,000 points used

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Great Salt Lake Bathymetry - South
7.6 million points 930 miles1,690
kilometers 381,000 points used
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Analog Data Examples
South Part
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Great Salt Lake Bathymetry
South Part
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North Deep Saturated? Layer?
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Ship Channel Little Valley Harbor
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Digital Data Examples
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South Part Lines 58 and 59
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South Part Lines 34 and 36
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Behrens Trench
Extreme south end of North part of Lake (line 8)
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Center of Lake (line 31) - North
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North central part of Lake (line 46) - North
Extreme North end of Lake (line 51) - North
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What the Great Salt Lake really looks like
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Raw data at ½ foot intervals
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North part contours and rasterized data
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South part contours and rasterized data?
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Threshold
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Great Salt Lake Bathymetry

• Data products
• Bathymetric maps of Great Salt Lake
• Open File Reports
• Methodsprocessingarea/volume table
• All on-line at http//pubs.usgs.gov
• North part OFR printed
• Digital data products
• Layered PDF (see example)
• Digital GIS data set (coming soon?)

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Other Tasks
3 stations 2 re-found Geodetic Grade Fully
documented
GPS vertical control
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T(w) T(a) RH
Quality-control for lake surface temperature
measurements
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Questions?