Finally, some good news. For decades, scientists have documented the decline in the clarity of Lake Tahoe. But using new, sophisticated methods to analyze environmental data, researchers believe the lake's clarity began stabilizing in 2001.

In their analysis released this week, scientists from the Tahoe Environmental Research Center at the University of California, Davis, don't attribute lake-clarity improvements to particular causes, though the report highlights programs initiated by area environmental agencies that have emphasized erosion-control methods and restrictive building regulations designed to curb runoff.

Scientists believe the lake's clarity is significantly influenced by "runoff of fine particles from both urbanized areas and roadways around the lake. Fine particles scatter light and limit how far into the lake we can see."

According to Geoffrey Schladow, a UC Davis professor of civil and environmental engineering who directs the Tahoe research center, the current analysis could signify the beginning of a long-term positive trend.

"From 1968 to 2000, there was a near-continuous decline in lake clarity," Schladow said in the report. "There were several years at a time when things seemed to improve, but invariably we returned to the same trend. But since 2001, we have had seven years in which the clarity has consistently been better than the long-term trend would have predicted. This is unprecedented."

Although the report portends good things for the lake's future, this is no time to let down our guard. On the contrary, we should step up efforts to aggressively protect the lake. As UC Davis scientists note, the report's seven-year time period is too short to definitively suggest lake clarity is improving.

But it's a tantalizing start. And that's certainly worth celebrating.