Lake Tahoe provides a unique opportunity for high altitude diving, and whether the dives are for recreation or ecological research, they allow for interaction with a unique and ever-changing ecosystem. Lake Tahoe is the largest alpine lake in the U.S. and rests on the border between California and Nevada.
According to the U.S. Geological Survey (USGS), Lake Tahoe was formed millions of years ago by the dual action of a geologic block fault and ancient glaciers. Lake Tahoe enjoys the distinction of being the second-deepest lake in the United States (behind Crater Lake in Oregon), with a depth exceeding 1,500 feet. With an average surface elevation of 6,225 feet above sea level, Lake Tahoe is the highest lake of its size in the United States.
Among the many winter sports, water sports, hiking and bicycling available at Lake Tahoe, an additional recreational activity offered at Tahoe is altitude diving. While high altitude scuba diving is a specialty and requires formal instruction, numerous dive shops in and around Lake Tahoe offer this kind of training.
When the surface of the water a diver is entering is 1,000 feet above sea level, or more, the rules for safe diving change. The rules must be followed precisely, or the pressure difference between the gases in the diver’s blood and the ambient atmospheric pressure at the surface of the water will cause painful air bubbles to form inside the diver’s body tissues in a condition known as bends. Experts caution that diving at altitude is much less forgiving than diving at sea level, so care must be taken to be precise during pre-dive calculations and teamwork during the dive itself. Even a seemingly simple mishap, like a stuck buoyancy jacket or inflator button, could have serious consequences in an altitude dive.
Both recreational and research divers have noticed differences in the changing ecology of the lake over the last half-century. The once minimalist landscape of the lake floor is now being populated by invasive plant and animal species that threaten to change the ecology and water quality of the lake. Invasive species that must be combated most notably include Eurasian water milfoil, curly leaf pondweed, and Asian clams.
The research and recreational altitude divers at Lake Tahoe are important for the help they provide in supporting the health of the lake’s ecosystem. Research teams from the University of California, Davis (UCD), began closely monitoring the lake 46 years ago. Since then, many changes have been observed.
A significant finding recently published in the UCD Tahoe Environmental Research Center (TERC) annual State of the Lake Report regards the effects of climate change. Researchers found that summer-like conditions have been extended at Lake Tahoe, which leads to a prediction that summer may be two months longer than it was in the 1960s, and maximum temperatures may rise eight degrees Fahrenheit, by the end of the 21st century. One possible consequence of the trend toward longer summers is a reduction in dissolved oxygen at the bottom of the lake which would change the over-all chemical balance within the lake, affecting fish and plant life. Data shows that changes could be noticeable within five to 10 years.
One interesting way to imagine the size, depth, and importance of Lake Tahoe is to consider that if all the water in Lake Tahoe spilled out over the state of California, the entire state would be covered by water to a depth of 14.5 inches. Drought conditions in 2013 influenced the total water level of Lake Tahoe, and the waterline is expected to fall below the level of its natural rim in late 2014. The larger regional ecosystem of the Tahoe Basin area depends on the health and proper management of Lake Tahoe, including its water quality, invasive species, and total water level.
The observations made by Lake Tahoe’s research divers, when paired with the sophisticated modeling predictions of UCDTERC, provide transferable technical information as well as solutions in microcosm that can be applied to other ecosystems and other circumstances around the world. While Lake Tahoe is in many ways unique, studies conducted in the Tahoe Basin ecosystem provide valuable opportunity and information. The water quality, fuels management and invasive species problems faced at Lake Tahoe are problems that will likely be faced elsewhere in the face of climate change.
Just as SCUBA rules change when diving at altitude, political rules change when funding becomes scarce. Altitude diving requires advanced skill applied with precision and speed in unforgiving circumstances in much the same way that the ongoing, successful, ecological management of Lake Tahoe requires advanced science applied with precision and speed to prepare for a likely unforgiving environmental future.
As the Lake Tahoe summit convenes in August, 2014, to determine federal assistance allocations, stakeholders in attendance will no doubt include research and recreational altitude divers. Altitude diving will continue in Lake Tahoe for both recreation and research no matter how the political leadership and stakeholders decide to manage the lake’s future.
By Lane Therrell