Lake Tahoe is the clearest it has been in 10 years. But researchers say they don´t know if it´s the result of scientific efforts to reverse four decades of declining clarity or part of a natural drought cycle in the Sierra. The specialists at the University of California-Davis say a white plate used to measure the lake´s clarity could be seen as deep as 78 feet on average in 2002. It marks the second year in a row of improvement and the deepest the dinner-plate sized disk could be seen since 78-point-three feet was recorded in 1992. Lake Tahoe´s clarity has declined roughly a foot a year over the past 40 years due to intense development around the alpine lake on the California-Nevada line. The disk could be seen at depths greater than 100 feet in 1968.
Research leader Charles Goldman says the new results are encouraging. But he warns that 10 years is a short time and that it is too early to tell if the recent improvements will continue.
Many of the improvement projects under way at the lake are aimed at reducing runoff of fine sediment and nutrients — including fertilizers that promote algae growth. They also are trying to reduce air pollution from vehicles in the lake basin and from smoke stacks outside it.