Heavy rainstorms that hit the Lake Tahoe basin at the beginning of 1997 caused rapid snowmelt and delivered huge amounts of nutrients and sediment into the lake, resulting in a loss of water clarity, UC Davis researchers reported recently. "The 1997 floods can be considered as a catastrophic hydrologic event at Lake Tahoe, which significantly re-sculptured the stream channels and greatly modified the deltas where the stream flows enter the lake," said John Reuter, a UC Davis researcher and director of the Lake Tahoe Interagency Monitoring Program. Water clarity data released by the UC Davis Tahoe Research Group last month showed that between 1996 and 1997 the transparency of Lake Tahoe declined by 12.9 feet, from 76.9 feet to 64 feet. UC Davis researchers including Reuter, Tahoe research group principal investigator Charles Goldman and Alan Jassby report that since Lake Tahoe clarity data collection began in 1968, such a significant change has been observed only one other time, in 1981-82. Water clarity changes from year to year are typically more on the order of three to seven feet per year when a decline is observed, the researchers say. Yet, while it is instructive to examine the year-to-year changes in lake clarity, Goldman says, "it is the long-term or decadal trends that provide us with the most useful glimpses into lake response to development and restoration."