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New Clarity Research

TitleNew Clarity Research
Author/CreatorCobourn, John; Purdy, Shelly; Segale, Heather M.
Related item(s)Press Release available at
Date Original2005-03-07
Summary/DescriptionLake Tahoe Report Segment #109 - "New Clarity Research" (airdate March 22, 2005). Researchers discuss one of the causes of water clarity loss in Lake Tahoe, fine particles sediment (tiny bits of rock) that get into the lake from runoff.
SubjectWater quality -- Tahoe, Lake (Calif. and Nev.)
LocationLake Tahoe (Calif. and Nev.)
Tahoe, Lake (Calif. and Nev.)
CollectionThe Lake Tahoe Report
Original PublisherLake Tahoe Environmental Education Coalition (
Electronic PublisherUniversity of Nevada, Reno - Department of Teaching and Learning Technologies
Ordering and Permissions InformationFor more information, contact the University of Nevada Cooperative Extension, or 775-832-4138.
Date Digital2006-02-15
RelationRequires Windows Media Player
Resource TypeMoving Image
Contributing InstitutionUniversity of Nevada, Reno
TranscriptionSegment A109: New Clarity Research Air Date: 3/22/05 Suggested Tease (none on tape): Researchers have pinpointed what they believe may be the single greatest problem causing the loss of clarity in Lake Tahoe. Shelly Purdy will have all the details of this new research coming up on the Lake Tahoe Report. Anchor Intro: Over the past two years in our weekly Lake Tahoe Reports, Shelly Purdy has reported on everything from algae growth to excess nitrogen to sediment as causes of Lake Tahoe's declining clarity. New research has now narrowed those choices down to one primary cause of clarity loss. Shelly has details in tonight's lake Tahoe Report. ((TAKE PKG)) ((nats lake shore)) ((Track 1)) Despite a lot of talk about the "greening" of Lake Tahoe…this body of water is still one of the bluest and clearest in the world. Millions of dollars are being spent and hundreds of thousands of man-hours are being used to protect Lake Tahoe. But what, exactly, does it need protecting from? Researchers have known for a long time that sediment is a problem…but new research suggests it's the tiniest of particles…about 10 microns or 1/10 of a millimeter in size…that are really causing all the trouble. ((sot @ 2:12 Brendan Ferry, Tahoe Regional Planning Agency)) "Those particles remain suspended in the moving water column of the lake and refract sunlight which makes the lake look less clear or a little more cloudy." ((Track 2)) And the thing that makes these tiny particles even more damaging is the fact that they never really settle to the bottom. In effect, every teeny tiny speck of dirt that goes into Lake Tahoe stays there…making the lake less clear and blue. ((sot @ 4:23)) "About every year the lake will mix to a depth of about 313 meters which is kind of the average depth of Lake Tahoe. So, a 10 micron or less size particle will take almost a year to settle down to that depth, but by the time it's settling, the lake itself is mixing and turning over. So, those particles are constantly being resuspended in the lake. ((Track 3)) So how do we fix the problem? Well, this type of dust and dirt comes from many sources like runoff and road dust. You don't have to look far around Tahoe to see storm drains clogged with mud and cars kicking up dust from the road. The best way to keep this dirt and dust from getting into the lake is to control it at its source. It's a daunting task, but something local agencies are taking-on full strength. With the Lake Tahoe Environmental Education Coalition, I'm Shelly Purdy for KOLO News Channel 8. Anchor Tag: The TRPA us using a concept called source control to tackle the sediment problem Shelly just explained. All property owners at Tahoe are now required to install Best Management Practices, or BMPs on their property. BMPs are erosion control measures like storm drains and native landscaping that hold soil in place and prevents erosion.

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