Tahoe Science Logbook: Winter weather does not stop research at Lake Tahoe
April 17, 2017
Everyone loves a big winter (especially when it follows a multi-year drought) and this was certainly a big winter. And despite technically being spring, there are plenty of days it still feels like winter. Skiers whoop through waist deep in powder, Lake Tahoe pours crystal clear water down the Truckee River, and UC Davis researchers pull their boat through the ice.
Wait … what? Yes, a big winter is good for the environment but researchers at the Tahoe Environmental Research Center struggle to keep their sampling schedule.
So what do the researchers do on the lake in winter conditions? Everything they do in the summer, they just wear more clothing.
Every 10 days (weather permitting) the lake gets a check-up. Scientists measure the lake's physical properties, temperature, oxygen content and nutrient concentrations (nitrogen and phosphorous) from top to bottom. These measurements confirm how deep the lake has mixed and what algae-stimulating nutrients will be available come spring.
Using specialized sampling equipment, phytoplankton (algae) and zooplankton (microscopic animals) samples are collected to see how these living populations are responding to the physical changes. Finally, researchers deploy instrument packages that measure inorganic particles in the water (road dust and silt from flood events), chlorophyll, and the amount of available sunlight at depth. Taken together, the data reveal the changing balance between algae growth and erosion in controlling clarity.
Oh, and of course, the lake's clarity is measured using a Secchi disk at high noon.
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Water clarity measurements have been taken year-round since 1968, providing researchers insight into what is having the largest impact on Tahoe's clarity. Recent analysis of the longterm data shows that winter clarity is improving. It is not uncommon to see Secchi readings in February and March that rival or surpass the 100-foot average depth recorded over a century ago.
However, summer clarity continues to decline, albeit at a slower rate than previous decades. While the verdict is still out as to why this is occurring, climate change resulting in a warmer lake may be a significant factor.
Conducting research on Lake Tahoe in winter-like conditions takes more motivation than boating under the summer sun. Each of the sampling tasks presents its own challenge in sub-freezing conditions. Wet equipment removed from the lake keeps the deck of the research vessel covered in a sheet of ice. Fine mesh nets stick to the metal boat and risk tearing. Battery powered instruments misbehave when their internal voltages plummet with the temperature.
Despite these inconveniences, winter is the most beautiful time to be on the lake. Recreational boats are long gone. Bald eagles perch in lakeshore trees hunting ducks that return north before the snow has even melted from the piers to claim their breeding grounds. The water color noticeably changes to a deeper blue, lacking any impurities that will come with the impending spring snowmelt.
A peace and quiet settles on the lake that just can't be found during the summer months. So while visitors and locals are enjoying the waist deep powder, TERC researchers are enjoying Lake Tahoe like it was 100 years ago.
Come discover the UC Davis Tahoe Science Center (www.tahoesciencecenter.com). Uncover the Tahoe Basin's ecological challenges through 3-D movies and interactive exhibits. Family friendly fun for kids ages 8 and up. Drop-in tours are Tuesday through Friday from 1-5 p.m. For school groups, we offer inquiry-based field trips. Check out our monthly lecture series on various scientific topics. To learn more about the Tahoe Science Center and TERC, visit tahoe.ucdavis.edu. The science center is located at 291 Country Club Drive Incline Village, Nevada. Call us at 775-881-7566.