New director for maritime museum

The Tahoe Maritime Museum Board of Directors announces the appointment of Jesse Siess Hadley as the Museum's new Executive Director, effective Jan. 1.

Jesse was previously the Executive Director of the Coachella Valley Historical Society in Indio, Calif. "The Board believes that Jesse brings the professional museum experience necessary to continue the Tahoe Maritime Museum's development as a World Class institution," according to a release.

Inspections ward off invasive mussels

Watercraft inspection data and scientific reports continue to indicate that Lake Tahoe’s waters remain clear of invasive Quagga and Zebra mussels, which are considered major threats to Lake Tahoe and surrounding waterbodies.

Tahoe Resource Conservation District watercraft inspectors performed 8,000 inspections this boating season, and there were an additional 19,000 launches comprised of watercraft with intact Tahoe-issued inspection seals.

“We’re very happy with the watercraft inspection program thus far,” said Patrick Stone, TRPA’s Senior Wildlife and Fisheries Biologist and lead for early detection monitoring of invasive mussels. “Investigations conducted around Lake Tahoe, Fallen Leaf Lake and Echo Lake confirmed that Quagga and Zebra mussels have not established in our lakes. These results are a credit to the inspection program.”

Concern among local agencies remains high as more Western waterbodies have shown evidence of invasive mussels and other aquatic invaders. Waterbodies in California and Nevada known to be infected with invasive mussels include San Justo Reservoir, Lake Mead, Lake Havasu and the entire Colorado River system. As watercraft continue to arrive from high risk waters, the importance of Lake Tahoe’s watercraft inspection program remains critical. Federal appropriations through the U.S. Fish and Wildlife Service in 2010 enabled the program to implement off-highway inspection stations. This created an opportunity to streamline inspection procedures and increase decontamination capacity.

2010 saw a dramatic increase in watercraft decontaminations, which doubled from approximately 600 in 2009 to 1,208 this year. Improved decontamination capacity at off-highway inspection locations allowed inspectors to be more thorough in treating high-risk watercraft. Additional improvements to inspection protocol allowed inspectors to increase prevention efforts by intercepting watercraft arriving from waters known to be infested with aquatic invasive mussels.

In total, 11 watercraft showing the presence of aquatic invasive species of concern were intercepted and decontaminated.

“It only takes one contaminated boat to introduce aquatic invasive species into Lake Tahoe,” said Tahoe RCD Biological Resources Program Manager Kim Boyd. “We need to remain vigilant and not let our guard down. We hope that by demonstrating the success of the watercraft inspection program for Lake Tahoe, the Tahoe RCD and its partners can create a model for prevention programs by sharing our resources and providing support. The TRPA, our key partner in invasive species prevention, continues to be instrumental in the success and evolution of this program.”

While the addition of convenient off-highway locations enabled boaters to receive their watercraft inspections and decontaminations when entering the Lake Tahoe Basin, marinas and boat launches continued to be the busiest locations for inspections in 2010. Cave Rock saw the most inspections, followed by the Tahoe Keys Marina, Lake Forest Boat Launch, Meyers Inspection Station, Alpine Meadows Inspection Station and Sand Harbor. Off-highway inspection stations accounted for approximately 31 percent of all inspections performed during the 2010 boating season.

This year’s prevention efforts also included a more rigorous non-motorized watercraft inspection process at ramp facilities, U.S. Forest Service kiosks and Fallen Leaf Lake. Tahoe RCD inspectors surveyed more than 1,900 paddlers to assess the risk of transporting aquatic invasive species from previously visited water bodies. Paddlers also were educated about self-inspecting and decontaminating canoes, kayaks and paddleboards.

Current information on the boat inspection program, including hours of operation for boat launches and snow closures, is available at http://TahoeBoatInspections.com or by calling 888-824-6267. For more information on the district, visit www.tahoercd.org.

NASA study finds Earth's lakes are warming

WASHINGTON -- In the first comprehensive global survey of temperature trends in major lakes, NASA researchers determined Earth's largest lakes have warmed during the past 25 years in response to climate change.

Researchers Philipp Schneider and Simon Hook of NASA's Jet Propulsion Laboratory in Pasadena, Calif., used satellite data to measure the surface temperatures of 167 large lakes worldwide.

They reported an average warming rate of 0.81 degrees Fahrenheit per decade, with some lakes warming as much as 1.8 degrees Fahrenheit per decade. The warming trend was global, and the greatest increases were in the mid- to high-latitudes of the Northern Hemisphere.

"Our analysis provides a new, independent data source for assessing the impact of climate change over land around the world," said Schneider, lead author of the study published this week in the journal Geophysical Research Letters. "The results have implications for lake ecosystems, which can be adversely affected by even small water temperature changes."

Small changes in water temperature can result in algal blooms that can make a lake toxic to fish or result in the introduction of non-native species that change the lake's natural ecosystem.

Scientists have long used air temperature measurements taken near Earth's surface to compute warming trends. More recently, scientists have supplemented these measurements with thermal infrared satellite data that can be used to provide a comprehensive, accurate view of how surface temperatures are changing worldwide.

The NASA researchers used thermal infrared imagery from National Oceanic and Atmospheric Administration and European Space Agency satellites. They focused on summer temperatures (July-September in the Northern Hemisphere and January-March in the Southern Hemisphere) because of the difficulty in collecting data in seasons when lakes are ice-covered and/or often hidden by clouds. Only nighttime data were used in the study

The bodies studied were selected from a global database of lakes and wetlands based on size (typically at least 193 square miles or larger) or other unique characteristics of scientific merit. The selected lakes also had to have large surface areas located away from shorelines, so land influences did not interfere with the measurements. Satellite lake data were collected from the point farthest from any shoreline.

The largest and most consistent area of warming was northern Europe. The warming trend was slightly weaker in southeastern Europe, around the Black and Caspian seas and Kazakhstan. The trends increased slightly farther east in Siberia, Mongolia and northern China.

In North America, trends were slightly higher in the southwest United States than in the Great Lakes region. Warming was weaker in the tropics and in the mid-latitudes of the Southern Hemisphere. The results were consistent with the expected changes associated with global warming.

The satellite temperature trends largely agreed with trends measured by nine buoys in the Great Lakes, Earth's largest group of freshwater lakes in terms of total surface area and volume.

The lake temperature trends were also in agreement with independent surface air temperature data from NASA's Goddard Institute for Space Studies in New York. In certain regions, such as the Great Lakes and northern Europe, water bodies appear to be warming more quickly than surrounding air temperature.

Tahoe analysis: Climate Change Forecasts

UC Davis scientists have issued the most detailed forecast to date of likely climate-change effects at Lake Tahoe, complete with estimates of when those effects might be seen and how big they might be.

Their findings suggest that even under the most optimistic projections:
* The average snowpack in the Tahoe Basin will decline by 40 to 60 percent by the year 2100.
* Floods will increase in the middle of the century.
* Prolonged droughts will become more common at the end of the century.
* A new threat to the lake's unique ecology, one that will come from the bottom of the lake, will become important by the second half of the century.

The report was written for the U.S. Forest Service's Pacific Southwest Research Station. Its lead authors are Robert Coats, a UC Davis researcher and consulting hydrologist, John Reuter, associate director of the UC Davis Tahoe Environmental Research Center, and Geoff Schladow, the center's director.

"Public dollars are funding restoration programs in the Tahoe region, which is a special place for millions of people," Schladow said. "For these programs to succeed, resource managers need to know what to expect in the coming decades.

"Will we have more or less snow, rain and runoff? Will the erosion controls and stormwater basins we are devising now still be useful in 30 or 50 years? What impact might climate change have for Lake Tahoe's water quality and aquatic ecology?" Schladow said.

In recent years, UC Davis researchers have drawn on 100 years of data to describe changes in temperature and precipitation that have already occurred in the Tahoe region.

The new report combines those findings with sophisticated computer models to produce detailed local projections out to the year 2100.

The scientists considered two possible future carbon emission scenarios: one business as usual, in which population growth and national and international policies affecting global climate change remain unchanged, and the other optimistic, assuming slower growth and aggressive climate action.

"While there is always some uncertainty when projecting this far into the future, the results appear reasonable," Reuter said. "They provide environmental managers and scientists with our first detailed glimpse of the potential impact of climate change on precipitation, runoff, water quality, and plant and animal resources in Lake Tahoe."

This glimpse gives scientists and resource managers a better chance of taking strategic steps to minimize coming impacts of climate change.

Those potential impacts include:

Precipitation

No strong increase in the amount of annual precipitation was predicted. However, the Tahoe Basin will see a continuing shift from snowfall to rain, as well as earlier snowmelt and runoff. Based on the modeling scenarios, by the end of the century, precipitation in some years could be all rain and no snow. The peak snowmelt in the Upper Truckee River will occur four to six weeks earlier by the end of the century.

Water flow and quality

Floods will be larger and more frequent in the middle of the century. Peak water flows in the Upper Truckee River, the largest river flowing into Lake Tahoe, will more than double, with the future 100-year flood resembling today's "1,000-year flood." Such high streamflows will threaten regional infrastructure (such as roads and bridges), the authors said.

In the case of water quality, the model simulations showed that, even though more stormwater runoff is forecast, today's best management practices will be able to accommodate the bulk of the increase. The simulations showed that predicted growth in runoff will cause only a 10 percent decline in the performance of urban stormwater control devices configured to current requirements.

Droughts

Droughts will be more severe, especially toward the end of the century and on the east side of the basin.

Truckee River water supply

Toward the end of the century, there are likely to be longer periods when the lake falls below its natural rim and water stops flowing into the Truckee River. (In the last 110 years, the lake has fallen beneath its natural rim on only 20 occasions, and only for a few months or years at a time.)

Under the "business as usual" scenario, these periods could be as long as 10 to 20 years. This would eliminate a large part of the downstream water supply for Reno, Pyramid Lake and agriculture. Under the "optimistic" scenario, these periods would last several years at a time and occur more frequently than in the past.

Lake turnover (vertical mixing)

The new analysis confirms the researchers' 2008 warning that climate change is likely to greatly alter water circulation in Lake Tahoe. By the second half of the 21st century, there are likely to be decades-long periods when the lake stops mixing to the bottom. (Historically, this complete mixing or turnover has occurred once every four years, on average.)

Turnover carries oxygen from the surface to the bottom of the lake. Without oxygen, a large part of the lake will be inhospitable to trout and other game fish.

Lake clarity may be impacted, as well. Prolonged absence of mixing could start a physical-chemical process resulting in the release of large amounts of phosphorus from the lake's bottom sediments. If this phosphorus reaches the surface, it will feed algae. Algae are one factor contributing to reduced water clarity. In addition, when algae sink to the bottom and decompose, oxygen is taken from the deep water, thus creating a downward spiral in water quality and clarity.

The authors conclude that public programs at Lake Tahoe to restore lake water quality (such as the Environmental Improvement Program and best management practices) are needed more than ever.

"The Total Maximum Daily Load program, which prioritizes fine-particle removal to improve clarity, may be the most important local action to be taken to help mitigate against climate change," Schladow said. "Phosphorus, the limiting nutrient at Lake Tahoe, will be reduced in direct proportion to the removal of fine particles, and this will help reduce the oxygen demand of the lake and increase its resilience to change."

There is little time to waste, said Robert Coats.

"Lake Tahoe is very close to at least two tipping points. First, a decrease in deep mixing could trigger abrupt changes in water quality and clarity. Second, our modeling results show that a decades-long shut-off of lake outflow by the end of the century is likely, cutting off a large part of the water supply for Reno and other downstream users."

"When we add the expected terrestrial impacts of increased drought - especially tree deaths and wildfire - it is clear that by 2100, the Tahoe Basin will be different from the one we know today," Coats concluded.

The new report has value to water resource managers beyond the Tahoe Basin, since many other lakes and reservoirs are likely to be affected by climate change. "Our team came away convinced of the value of early collaboration between the science community and regional resource managers," Reuter said.

The study was funded by the U.S. Forest Service and the U.S. Bureau of Land Management, through the Southern Nevada Public Lands Management Act.

The report's research collaborators included Goloka Sahoo (UC Davis), Mike Dettinger (U.S. Geological Survey and Scripps Institution of Oceanography at UC San Diego), Brent Wolfe (Northwest Hydraulic Consultants), John Riverson (Tetra Tech, Inc.) and Mariza Costa-Cabral (Hydrology Futures, LLC).

Rubber mats killing Tahoe's clams

Rubber mats laid atop beds of Lake Tahoe's invading clams seem to have done their deadly job, according to reports from the Tahoe Resource Conservation District.

In early November, divers removed mats from two half-acre-sized swaths of clam-infested lake bottom. While data still are being analyzed, the test indicates the mats appear to be the most effective weapon against Tahoe's Asian clam population, experts have said.

"There are definitely lots of visibly dead clams," said Kim Boyd, an invasive species specialist with the Tahoe Resource Conservation District. "It looks very promising."

The mats, measuring 10 feet wide and 100 feet long, kill clams by robbing them of oxygen and nutrients. The mats were laid on the lake bottom in July at Marla Bay and South Lake Tahoe's Lakeside Marina.

The $648,000 experiment was built on a previous test in 2009 suggesting "bottom barriers" were effective in killing the dime-sized clams. But this one targeted them on a larger scale. Scientists first noticed Asian clams in Tahoe's waters in 2002, but they have since exploded in number, infesting a large part of the southeast corner of the lake. They also have become established on a football field-sized piece of lake bottom near the mouth of Tahoe's landmark Emerald Bay.

Clams can adversely impact Tahoe's sensitive ecology and are linked to blooms of noxious algae. A bigger danger, experts say, is that the clams could elevate calcium levels in the lake's waters to the point they could support populations of quagga or zebra mussels, which would have devastating effects on Tahoe's ecology and economy.

"The fear is Asian clams could facilitate the introduction of the quagga," said Geoffrey Schladow, director of the University of California, Davis Tahoe Environmental Research Center.

Researchers now will study the areas the mats were laid to determine how quickly Asian clams recolonize on the bottom. They also want to study long-term impacts on other macroinvertebrates native to the lake, such as pea clams, Boyd said.

Other, smaller tests are planned in Marla Bay to gauge effectiveness of the mats in killing Asian clams during the winter, when cold water temperatures are thought to shut down their metabolism and make them invulnerable to this particular method of control, Boyd said. If bottom barriers still can be effectively used in winter, she said they would prove much more valuable over the long run.

By late February, researchers plan to install some barriers in Emerald Bay to determine their stability when encountering underwater turbulence produced by paddle-wheel tour boats, Boyd said. Scientists said they hope to begin using the mats to kill Emerald Bay's clams after next summer's boating season.

While the barriers appear effective, Asian clams probably will always have an unwelcome presence at Lake Tahoe, Schladow said.

"Eliminating them probably isn't feasible. Controlling them could be possible," Schladow said.

Photo: UC Davis