Eyes down

Local divers monitor Lake Tahoe's water quality

Diver Martin McClellan  installs an

Diver Martin McClellan installs an

Lake Tahoe’s nearshore zone—an area that extends from the shoreline out 350 feet into the lake, or to 69 feet of depth—is known for its exceptional clarity. That’s changing, says Reno resident Martin McClellan, manager of a local SCUBA project called Project Baseline Tahoe.

Tahoe’s nearshore zone is the area of the lake most strongly affected by onshore pollution and human activity. It is also the zone where people most frequently interact with the lake, through activities like kayaking, swimming and SCUBA diving. McClellan, who has been SCUBA diving in Lake Tahoe for more than 30 years, noticed over time that clarity at dive sites in the nearshore zone was getting worse and worse. “We were hearing reports that the clarity of Lake Tahoe was improving,” McClellan said. “Well maybe it is, three-quarters of a mile off the shoreline, in a water column of 1,000 feet. But it’s not improving where you and I use that lake.”

Since 2010, McClellan has been working to document changes that he and other divers observe in Tahoe’s nearshore zone under Project Baseline Tahoe. The project began with a “stake in the sand” at underwater locations in Sand Harbor and Glenbrook Bay. “We began by literally putting a stake in the sand, and going back to the same spot each time to get depth, temperature, to assess visibility, and to take a repeatable photograph,” McClellan said.

In 2011, Baseline Tahoe’s team upgraded the “stake-in-the-sand” system, installing visibility monitoring stations at Glenbrook, Sand Harbor, Carnelian Bay and Hurricane Bay. Each site consists of a depth benchmark, a temperature gage, and visibility marker stakes that lead away from the station at ten-foot intervals. Any diver who visits the stations can read the gages, then send data and photographs to McClellan, who compiles and enters them into Project Baseline’s database.

McClellan works with 12 divers from California and Nevada to collect data at the monitoring stations, and to expand the current system. The team recently added a station near Bliss State Park, and in August, received a $3,000 grant from the Tahoe Truckee Community Foundation that will be used to upgrade two stations with digital depth and temperature sensors. They will also move one existing station from Carnelian Bay to Tahoe City, close to where lake water enters the Truckee River. Scientists from University of California, Davis and the Desert Research Institute in Reno are also monitoring water quality in deep areas of Lake Tahoe and in the nearshore zone. But many of them work from above the surface.

“Martin’s group is doing very important work to understand changes in the lake from an underwater viewpoint,” said University of Nevada, Reno researcher Sudeep Chandra. “It gives the scientific community a frame of reference that is different from what we would do with our instruments.”

McClellan’s team has partnered with Chandra his students on several past projects, including a recent effort to map underwater plant life in Lake Tahoe. “Water quality measurements are really a way to get our teams out the door,” said Todd Kincaid, one of the founders of the global Project Baseline. “What I really hope is that eventually all our teams will organically cultivate these types of collaborative relationships with other entities, either academic or management or both.”