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Near Shore Studies

Ken TaylorRick SusfalkMargaret Shanafield

Desert Research Institute

Funding provided by:

Nevada State Lands (Tahoe license plates)

California Lahontan Regional Water Quality Control Board

TRPA

Near shore zone:

Fast and local response to land use changes.

C

larity: greatest depth a Secchi disk is visible

turbiditychlorophylltemperature

Sample inlet is1 foot below surface

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Snapshot DayMay 10, 2003

InclineKingsBeach

Star Harbor

Emerald Bay South

Shore

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Cebta distance profile

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UpperTruckee

BijouCreek

StateLine

SkiRun

July 112002

Calm

Edgewood

Oct 222002

Calm

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

Edgewood

Nov 132002

2 inchsnowonshore

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

021218

Dec 182002

Calmandcold,Keysfreeze

TahoeKeys

UpperTruckee

BijouCreek

SkiRun

030108

Jan 082003

2 feetof snowonshore

TahoeKeys

UpperTruckee

BijouCreek

SkiRun

Jan 202003

Calm

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

Edgewood

Jan 292003

2 daysafter rain onlakeshore snow

TahoeKeys

UpperTruckee

BijouCreek

SkiRun

Jan 292003

6 daysafter rain onlakeshore snow

TahoeKeys

UpperTruckee

BijouCreek

SkiRun

Feb 172003

After 4 inchsnow onshore

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

April 52003

calm

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

Edgewood

April 192003

Afterlakelevelrain

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

April 42003

After6 inchsnow onshore

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

May 13,2003

Calm,spring run off

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

May 222003

Calm,springrun off

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

June 52003

Calm,end of run off

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

June 242003

After rain

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

Edgewood

July 032003

calm

TahoeKeys

UpperTruckee

BijouCreek

StateLine

SkiRun

Edgewood

Collect particlesample on 0.1 micron filter

Examine with scanning electron microscope

Boat photo 1 micron

UpperTruckeeoutlet

Organic

Boat photo

SandHarbor

1 micron

Mineral

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Elemental composition ofparticles off Bijou Creek

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UpperTruckee Bijou

Creek

StateLine

SkiRun

Edgewood

Algae

Minerals

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UpperTruckee Bijou

Creek

StateLine

SkiRun

Edgewood

Highest turbidity

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Near Shore Zone

Only a few areas have a problem.

Mineral particles from some, but not all, developed watersheds are the biggest problem.

Near Shore Zone

Biggest problems occur during lake level snow melt and spring run off.

How can we keep the small mineral particles out of the lake?

Littoral Zone Turbidity Threshold

1 NTU (Secchi clarity of ~4 m) away from streams

3 NTU (Secchi clarity of 1 to 2 m) for areas influenced by a stream.

Is occasionally exceeded.Insignificant protection for lake.

near shore zone clarity monitoring program is the ONLY way to determine the effectiveness of management actions on near shore clarity.

Near Shore Zone Clarity

A near shore zone clarity monitoring program is the ONLY way to determine the effectiveness of management actions on near shore clarity.

Monitoring

Identify location of problem areas to focus management actions.

Determine trends to evaluate effectiveness of management actions.

Whole lakeshore surveys in winter, spring and summer, to identify locations and spatial extent of problem areas. (Use the boat)

Continuous measurement of major problem areas (7 to 10 areas), to determine temporal trends. (Use moored instruments)

Current Near Shore Monitoring:

• 4 times a year

• Calm conditions

• 9 locations

• Water depth of 25 m

Cannot identify problem areas or trends.

But… There is no near shore zone monitoring program.

Mineral particles, not algae, is the biggest problem.

Suggested Monitoring

Whole lakeshore surveys, to identify locations and spatial extent of problem areas.

Continuous measurements, to determine temporal trends.

Near Shore Conclusions

Several problem areas, caused by mineral particles from developed areas

Ineffective regulatory threshold

No way to determine effectiveness of management actions or trends

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Report is available at:

http://tahoenearshore.dri.edu

Lake level snow melt greatly increases turbidity of near shore waters by adding mineral particles to lake.

Upper Truckee, Bijou Creek, Ski Run

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