News
LAKE TAHOE — The 2007 Angora fire has had no significant impact on Lake Tahoe's famed clarity, experimental methods to control invasive clams are working, pollutant phosphorus is at its lowest levels in 29 years and free-floating algae in the lake have remained constant since 1996, according to the most recent State of the Lake Report.
The University of California, Davis, on Tuesday released the 2010 State of the Lake Report, which compiles all the data derived from diverse research projects conducted in 2009 and places it in the context of the long-term scientific record.
“Overall, we remain cautiously optimistic,” said John Reuter, associate director of the UC Davis Tahoe Environmental Research Center.
Earlier this month, scientists reported a slight decline of 1.5 feet in lake clarity from 2008 to 2009.
The rate of decline in Lake Tahoe's clarity since 2000 was less than that seen in past decades, said Geoffrey Schladow, director of TERC.
“This report is an impartial, annual accounting of many key variables of lake change,” Schladow said. “It helps us all recognize the differences between natural variability and long-term change, and how our efforts toward the restoration of Lake Tahoe are progressing.”
Despite the good news, Reuter cautioned the lake and its surrounding ecology are still in peril.
“(Lake Tahoe's ecology) does have the ability to improve, provided that pollution control is achieved,” he said.
The University of California, Davis, on Tuesday released the 2010 State of the Lake Report, which compiles all the data derived from diverse research projects conducted in 2009 and places it in the context of the long-term scientific record.
“Overall, we remain cautiously optimistic,” said John Reuter, associate director of the UC Davis Tahoe Environmental Research Center.
Earlier this month, scientists reported a slight decline of 1.5 feet in lake clarity from 2008 to 2009.
The rate of decline in Lake Tahoe's clarity since 2000 was less than that seen in past decades, said Geoffrey Schladow, director of TERC.
“This report is an impartial, annual accounting of many key variables of lake change,” Schladow said. “It helps us all recognize the differences between natural variability and long-term change, and how our efforts toward the restoration of Lake Tahoe are progressing.”
Despite the good news, Reuter cautioned the lake and its surrounding ecology are still in peril.
“(Lake Tahoe's ecology) does have the ability to improve, provided that pollution control is achieved,” he said.
State of the Lake
Below is a list of conclusions revealed in the 2010 State of the Lake Report.
Angora fire • Most nutrient and sediment concentrations in Angora Creek increased for the two years since the fire • Despite an increase in phosphorus and other constituent loads immediately downstream of the burn area, the overall impact on the Upper Truckee River and Lake Tahoe was insignificant. Asian clams • A control methodology to use rubber mats to deprive invasive clams of oxygen was tested and found to produce 100 percent mortality in Asian clams. • A large scale experiment is currently underway to test the long-term effectiveness and deployment costs of an expanded control program. • A multi-agency boat launch inspection and education program for all invasive species is an important component of the invasive species strategy. More than 20,000 boats were inspected in 2009. Mussels were found on ten of them. Weather • The nightly minimum temperatures recorded at Tahoe City have increased by more than 4 degrees F since 1910. • Days when air temperatures averaged below freezing have generally decreased by 30 days per year since 1910, although 2009 was a colder than average year. • Since 1910, the percent of precipitation that fell in the form of snow decreased from 52 percent to 34 percent. • Peak snow melt averages 2 1/2 weeks earlier than in the early 1960s. • Precipitation in 2009 was slightly below the long-term average, but significantly wetter than the previous two years. This was largely due to exceptionally high spring precipitation (March and May). • The decline in the percent of snow in 2009 was consistent with the long-term trend. Physical properties • Lake level fluctuates throughout the year, and from year to year. • Water temperature (volume averaged) rose by more than 1 degree Fahrenheit in the past 38 years. • Surface water temperatures have risen since data collection commenced. • Density stratification of Lake Tahoe has increased over the last 39 years as surface water warmed due to climate change. • In 2009, lake level fell to a low of 6222.76 feet on Dec. 31, almost 3 inches below the natural rim. For over two months there was not outflow from Lake Tahoe to the Truckee River. • Winter surface water temperatures were higher in 2009, due to the absence of deep mixing. • The maximum depth of mixing in 2009 was approximately 700 feet. Biology • Primary productivity, the rate at which algae produce biomass through photosynthesis, has been generally increasing since 1959. • The average annual abundance of algae (by concentration of chlorophyll-a) has remained relatively uniform since 1996. • Since 1984, the annual average depth of the deep chlorophyll maximum has declined. • Diatoms remain the dominant algal species and provide high quality food for aquatic species. • While phosphorus limited in the early part of the year, the lake is generally co-limited (needing both nitrogen and phosphorus) for optimum algal growth. • Periphyton (attached algae) concentrations were similar to values recorded in 2008, with the exception of Tahoe City, which experienced a 60 percent decrease to the highest values ever recorded at that site. • Periphyton distributions were significantly elevated along the north-east shoreline of the lake. |
