Researchers study Lake Tahoe water movements

SOUTH LAKE TAHOE -- It may look calm and peaceful to the human eye, but research shows Lake Tahoe is anything but placid underneath the surface.

Its waters are constantly rocking up and down and shifting from side to side. Sometimes they’re churning clockwise — in other areas, counter-clockwise.

The lake is an extremely variable and complex environment, and one of the few things scientists do know about it is that they know very little about water movements, said Dr. Geoff Schladow, director of the Tahoe Environmental Research Center.

That was one of the things discussed in a TERC presentation Thursday that shared new research on water circulation patterns in Lake Tahoe.

“Lake motions are important,” Schladow said to a group of about 30 or so people at Round Hill’s Elks Point Fire Station. He added, “It’s the currents, it’s the motions, that transport everything in the water.”

Understanding the movement of water in Lake Tahoe is important for a variety of reasons, Schladow pointed out. It helps researchers better identify the potential paths of harmful pathogens and substances in the lake, as well as the spread of invasive species.

He said there are several factors that effect the lake’s movement, but wind is the main one.

“We all think, ‘Oh, Tahoe, wind comes from the southwest,’” he said. “It does a lot of the time, but it comes from the southwest when you measure it at the airport.”

Schladow presented several models of wind patterns showing pockets of swirling air currents around the lake. Some were traveling in different directions than others.

Other data showed how wind pushes one side of the warmer, and lighter, surface water down deeper —the colder layers beneath it also get pushed down as a result — to begin a rocking motion throughout the lake.

“There are motions everywhere,” he said, “not just next to where the wind is blowing.”

Showing this a little more clearly, another model separated the lake into small grids — which were then separated into even finer grids in the nearshore — to get a better idea of water movement at the lake.

The idea is that these models can be used as tools to help protect drinking water quality at Lake Tahoe by better recognizing the pathways of pathogens.

Additionally, TERC has launched a “nearshore network” of monitoring stations to further measure water quality at the edges of the lake — an area researchers no little about.

“It’s the idea that we can monitor the nearhore in real-time,” Schladow said. “It’s not that hard to do. It’s the data we’re interested in, and we think it’s the data that’s needed.”

The nearshore network instruments sit at the bottom of about 2 meters of water and measure things like water temperature, turbidity and algal concentration.

Five stations are already installed in the lake. Schladow said a sixth is expected to go in at Sand Harbor in the next few weeks.