Lake Tahoe’s clarity is currently not declining and its outlook is positive, suggests data from a collaborative effort of UC Davis researchers, the Tahoe Regional Planning Agency and the Tahoe Environmental Research Center.
“In terms of clarity, the outlook is hopeful,” said Dennis Oliver, public affairs director of the TRPA. “There’s been quite a lot of progress made to undo the damage that was seen here in the 1950s.“
Likewise, Geoff Schladow of the Tahoe Environmental Research Center, said, “Because of all the projects that are being done every year, we’re going to make more progress. I’m cautiously optimistic.“
Since 1968, UC Davis researchers have been measuring the clarity of Lake Tahoe. According to experts, the clarity of the lake is an overall indicator of the health of the waterway.
When measurements began, the visible average depth of clarity was 102.4 feet. Last year UC Davis reported that since 2001 the lake’s clarity hasn’t been declining as fast as it had in previous decades. Data from 2008 confirms this – last year’s average was 69.6, compared with 2007‘s average of 70.1 feet.
Researchers are able to accurately measure the clarity of Lake Tahoe’s water by using a 10-inch diameter “secchi” disk. Light penetrates the water and bounces off of the disk, allowing the observer to see it at a specific depth. At some depth, however, the fine particles and algae present in the water absorb the light, and the disk can no longer be seen.
The deeper the disk can be seen clearer the water; if the disk can only be seen at a shallow depth, the water is said to be less clear.
In addition to clarity measurements, a multitude of tests are currently performed on the lake’s water – including bacteria levels, temperature, oxygen levels and pH – giving experts an accurate indication of pollution and adverse changes to the lake and its wildlife.
Formerly, there was a 40-year-long decline in Lake Tahoe water clarity, and improvement projects were scarce. During the past 10 years, however, enough money was received from public and private sectors to fund environmental improvement projects, totaling $1 billion. Half of these funds were allocated specifically for water quality projects.
“Twenty-six acres of state highway were outfitted with water treatment, which provides advanced treatment of water before it gets to the lake,” Oliver said. “Also, we were able to remove about 60 miles of forest roads no longer needed … and the momentum still exists to continue these projects.“
This ambitious funding has not been spent in vain, for the decline in water clarity is starting to level off, and restoration movements are likely to continue.
As part of the restoration project, hundreds of millions of dollars are being spent to stop storm water and other pollutants, often runoff from golf courses, paved roads and private lawns, from entering Lake Tahoe and affecting its water quality in a negative manner, Schladow said.
Lake Tahoe has long been a place of recreation for UC Davis students, Northern Californians and Nevadans alike. But with such a large tourist population, pollution is inevitable.
“I think most of [the pollution] is human-caused. How can we continue to live here without having negative effects on Lake Tahoe? That is an important question,” Schladow said.
Oliver expressed similar concerns.
“We must balance [human populations] with environmental concerns, and the way to do that is with technology and sustainability,” Oliver said. “We’re also concerned about wildlife, air quality, scenic conditions and rural character.“
Experts are optimistic about Lake Tahoe’s future in part because a bill will be introduced before Congress this year backed by California and Nevada senators.
“We’re starting to see the lake is responding [to restoration projects] and the line is flattening. Over the next 10 years and $2.5 billion worth of work, we’re hoping that we’ll turn the corner,” Oliver said.
MICHAEL MILLER can be reached firstname.lastname@example.org.