Tahoe Resort Report: Opening day for Northstar, Heavenly (video)
The fate of plastics in Lake Tahoe?
If the sun hits the blue waters of Lake Tahoe just right, and it’s a calm day off the point where the Cal Neva Resort & Casino sits quiet, stand up on your paddleboard or lean over the bow of your kayak and look for plastic floating on the surface or at varying depths.
Following major wind events, you might find a mini “garbage patch” forming on the surface.
Surface currents formed by wind create two large systems of rotating currents that mimic an ocean gyre, one on the north end of the lake and one on the south. Gyres are generated by three phenomena: global wind patterns, Earth’s rotation and Earth’s landmasses. The mountains affect wind patterns in the lake allowing smaller gyres to also manifest near the shoreline, in coves or around inlets.
The large gyre near the North Shore circles counter-clockwise and on the south another circles clockwise, coaxing plastics as well as other debris to collect in specific areas of the lake. Litter on the North Shore can get carried west from Sand Harbor to Hidden Beach and continue to Kings Beach.
As a result, patches of plastics can be seen in the water within a couple of hundred yards from the shore, specifically between the spot where old hot springs sit at Brockway Springs Drive and Stateline Point near the Cal Neva.
UC Davis, Tahoe Environmental Research Center (TERC) researchers created a computer simulation of surface currents for a 2-1/2 day period in August.
“The currents are ‘driven’ by the wind, which is recorded every 10 minutes on buoys and docks at 13 locations at Lake Tahoe,” explained a team of researches with the Tahoe Environmental Research Center in a description of the simulation. .
“At the beginning of the model run (time 0) a set of colored ‘balls’ are distributed across the lake surface – a different color in each quadrant. Watch as the currents then move them about. The green arrows also show the current velocity and direction across the lake.
“While the motion may at first appear chaotic, notice that there is a lot of regularity to the motion. There are two main circles (or gyres) that the balls trace out. These gyres are usually anti-clockwise in the north, and clockwise in the south. Sometimes there are smaller gyres closer to shore, especially at the very south of the lake. Things to note are the time it takes these gyres to undergo a complete revolution (about 1.5 days) and the pulsating motion that the gyres exhibit. This is due to the daily variation in the strength of the winds at Lake Tahoe, with stronger winds typically occurring in the afternoon,” they explain.
Understanding surface currents is important because currents are responsible for the transport of contaminants, invasive species, urban storm water and floating debris.”
NEW STUDIES START
Heather Segale, TERC education and outreach director, talked about funding received to study the fate of microplastics in Lake Tahoe and how it will be utilized.
“The research UC Davis is doing right now is looking at the fate of the microplastics (in Lake Tahoe) … because most of the research that has been done on microplastics and plastic pollution has been based on oceans.”
Segale added, “More types of plastics will float and float longer (in salt water)” as compared to less dense fresh water where not as many types of plastic float and the ones that do, don’t float as long.
Salt, temperature and pressure affect water density. Salt water is more dense than fresh water and as the temperature or pressure increases, density increases for both salt and fresh water.
Fresh water is most dense just above freezing, becoming less dense as water temperatures rise.
“Our research right now is looking at the fate of those plastics. Are they mostly staying at the top? The answer is no, not really,” Segale said. “Are they going down… where the density gradient changes from where the warmer water sits on top of the colder water? Or are they sinking to the bottom? Or are they getting eaten up by the different filter feeders that are in the lake like kokanee salmon or zooplankton?”
At Hidden Beach in Nevada, debris gets pushed on shore after one of these wind events, Segale said, emphasizing “the amount of plastic we found these couple of times that we’ve gone after a wind event is just incredible.”
Where plastics get deposited and what effects the Lake Tahoe environment have on the plastic is something UC Davis TERC is looking to learn.
8,000 POUNDS PULLED OUT
According to the United States Department of Justice, it wasn’t that long ago that dumping became illegal in the U.S.
“Beginning in the 1970s, Congress enacted a set of laws to protect the nation’s air, water, and lands from uncontrolled pollution,” the Justice Department website states. “These laws responded to the consequences of unregulated industrial development that had fouled those resources to the point where rivers were not fishable, air was unhealthy to breathe, and land contamination put Love Canal at the forefront of national consciousness.”
Over 8,000 pounds of garbage have been pulled out of both Lake Tahoe and Donner Lake over the last two years. In addition to the obvious pieces of plastic from trash not properly disposed, smaller pieces often invisible to the naked eye are also being carried by Tahoe’s currents around the lake.
“We are seeing lots of trash from decades ago, things like a bicentennial diet Pepsi can,” said Colin West of Clean Up the Lake, which over the last two months managed crews that pulled up most of that garbage.
Polypropylene sandbags are one example of what could be adding to the microplastics in Lake Tahoe. Tarps made of the same material are also commonly used around the lake to cover boats, kayaks and protect things from the wind and the sun’s rays, the exact thing that speeds up the deterioration of the plastic.
Ultraviolet rays “increase the degradation rate” of woven polyethylene. Sandbaggy, a high-end manufacturer, states “our sandbags have 1600 (hours) of UV protection, meaning they can last for about six months under the sun before deteriorating.” Yet, at a minimum, most sandbags used for construction on the shores of Lake Tahoe are in place for the duration of a two-year building permit.
It’s important to note that larger projects often take several years to complete.
“My research so far has not shown a definitive remove-by date,” said Jeff Cowen, public information officer with the Tahoe Regional Planning Agency. “However, since we do not allow this kind of pollution, there may be a guideline somewhere that needs to be better described.”
Michelle Gartner is a freelance writer who lives in Gardnerville, Nevada.
Coronavirus cases in Nevada, Placer counties grow at slower pace than state; Placer added to ‘monitoring’ list
UPDATE: Placer County has been placed on the state’s COVID-19 Monitoring List as of July 9, according to a news release. If the county remains on the list for three consecutive days, some businesses will be required by the state to close indoor operations for a minimum of three weeks.
The following businesses are urged to prepare for a shift to outdoor operations:
- Dine-in restaurants
- Wineries and Tasting Rooms
- Family Entertainment Centers
- Movie Theaters
- Zoos and Museums
In addition, all brewpubs, breweries, bars, and pubs would need to close, both indoors and outdoors, unless they offer sit down, dine-in meals. Stay tuned to this page for updates as to when these requirements may go into effect. Learn more
As California coronavirus cases continue to climb at record levels — with more than 11,000 reported in a 24-hour period Tuesday — Nevada and Placer counties see a climbing number of cases but at a slower pace than statewide testing.
The statewide positivity rate in testing was 7.1% over a 14-day stretch ending Tuesday, according to the state Department of Public Health.
Since July 2 reporting, Nevada County has recorded an increase of 38 cases, among 1,270 tests conducted for a 3% positive case rate. Over the past 14 days, the positivity rates has been 2%.
In the past week, Placer County’s rate was 7%, with 3,862 tests performed and 269 new cases reported on its coronavirus dashboard, but at a 4.5% rate over a 14-day period ending Tuesday, according to state data.
As of Thursday morning, neither county had yet been added to Gov. Gavin Newsom’s coronavirus county watchlist, which included 26 counties — Napa, San Benito and Yolo were added Wednesday.
Eastern Nevada County had 96 cases reported as of Thursday, with an additional 59 cases in western county. Those numbers reflect an increase of 32.4% total cases, against an increase of 18% in testing. East county saw an increase of 15 positive cases, while western county recorded 23 new cases.
Countywide there are 57 active cases, according to Nevada County’s coronavirus dashboard, which is up from 33 cases reported on July 2. Nevada County reported three hospitalized patients as of Thursday morning. One person has died in Nevada County.
Eighty-eight of the county’s cases are within the 96161 Truckee zip code, while another 20 are within Grass Valley’s 95945 and 16 others are within 95949 in western county.
Among all Nevada County’s case total, 63% have been reported as recovered.
Placer County’s case total was 993 as of Thursday, up from 724 last week. Of the case total 664 “likely recoveries” have been reported, according to the county’s coronavirus website. State data shows 55 hospitalized patients, including five in intensive care units. Eleven people have died.
The majority of Placer County cases have been logged in South Placer, which saw 208 new positive tests over last week. East Placer, which includes the north shore of Lake Tahoe, had an increase of 17 positive cases.
Statewide, California had a total of 289,468 cases with 99,246 new cases in the past 14 days. Total deaths stood at 6,582, with 930 deaths in the past 14 days.
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