State of the lake
August 16, 2014
Temperatures are getting warmer at Lake Tahoe, resulting in longer summers and some concerns about the lake's long-term stability.
During the past 100 years, air temperatures have increased about 5 degrees at the alpine lake. They could increase by another 8 degrees by 2100, resulting in an extra several weeks of summerlike conditions, according to scientists.
"None of the models predict that it's a flat line or that (temperatures) are going down," said Geoff Schladow, director of the Tahoe Environmental Research Center at U.C. Davis. "So things are changing. And for us as scientists or for agencies, this is difficult to try to work and plan in a time of change."
This and more was discussed in the 2014 State of the Lake report, which Schladow presented Thursday at the Tahoe Center for Environmental Sciences in Incline Village.
Climate change was a big topic of discussion at the meeting along with the ongoing monitoring of the lake's nearshore and clarity.
As for air temperature, Schladow said the actual change is modest, but where it has a bigger effect is on the lake itself.
If the lake's surface continues to warm, the difference in density between the water on top and the cooler water below could make it harder for the lake to mix. A likely effect is a reduction in dissolved oxygen, which would affect the lake's chemical balance and marine life.
According to TERC, Lake Tahoe did not mix to its full depth last year for the second year in a row.
"To me this is the biggest worry about warmer temperatures," he said, adding later that reducing algal growth in the lake could be a solution to slowing down the rate of consumed oxygen.
Other areas scientists are keeping an eye on are the threat of invasive species, the spreading of shoreline algae and even the possibility of a super storm.
Schladow spent a few minutes explaining the potential effects of a major storm, including the small possibility of 14-foot waves crashing on the shores of Incline Village.
That scenario doesn't seem likely at the moment since the lake's surface is barely over its natural 6,223-foot rim. The water level did rise six inches during the spring snowmelt, but that is one of the lowest increases recorded, according to TERC.
On the other hand, dry conditions have resulted in less sediment flowing into the lake the past couple years. Water clarity, as a consequence, continued to slow down in 2013. It measured at 75.3 feet.
TERC Associate Director Zachary Hymanson said many people contributed to the change.
"The science community has played a major part," he said in a statement, "but it needed agency participation, public buy-in, and funding from all levels of government and the private sector."
Schladow said there are many good things happening at the lake in addition to the progress made on clarity. One of them is the launch of a new network of nearshore monitoring stations around the lake.
The stations measure the health of the lake's nearshore, including the cloudiness, algae and particles in the water. Each has built-in sensors and takes samples about every 30 seconds.
The first was installed at Homewood on Monday.
"We would like to have something there so we know what's the response to that sort of storm, what's the response of the whole lake during spring runoff (and) what happens when we have strong northerly winds," Schladow said.
Scientists are also able to use an array of new modeling tools that help them better understand the lake itself, he said. Schladow showed one model that demonstrated the movement of particles after hitting the water.
"We're starting to build an idea about how water moves," he said. "How pollutants from fireworks, how pathogens from people swimming in the lake, will move."
Looking forward, Schladow said researchers are hoping to move beyond monitoring to find solutions to their concerns.
A couple things scientists are looking into at the moment are the use of detention basins — which would act as filtering systems for runoff water heading toward the lake — and increasing public engagement.
For the complete 2014 State of the Lake report, go terc.ucdavis.edu.