Experts: Wet winter would hurt Tahoe’s clarity

By Kathryn Reed

Lake Tahoe’s clarity will take a serious hit if El Nino materializes this winter.

That was the message delivered Tuesday night by a panel of stormwater experts.

Winter is coming – Is Lake Tahoe Ready? was the subject of the talk hosted by the League to Save Lake Tahoe on Oct. 13 at Lake Tahoe Community College. No, was the simple answer.

While predictions of a grand El Nino keep being reinforced by weather experts, the fact is the Lake Tahoe Basin is on the northern end of the weather system’s path. Today the chance of a significant El Nino for this area is a little more than 30 percent.

It was also pointed out that El Ninos have meant extreme wet and extreme dry winters for Tahoe. Which it will be is not ascertainable by the experts’ models.

“If we have a big year, we’ll see the effects of that. That doesn’t mean we won’t recover,” said Alan Heyvaert with the Desert Research Institute in Reno. “If we have a big rain year, we will see the lake degrade.”

While public landowners throughout the basin have put in a billion dollars worth of stormwater systems in the last 15 years, they are for the most part designed for the 20-year storm. That means if something more extreme arrives, the systems may overflow, causing untreated water to reach Lake Tahoe. This in turn degrades the clarity.

For Russ Wigart, who heads El Dorado County’s stormwater program, he is more concerned about the 100-year runoff than the 100-year storm.

Wigart and Jason Burke, stormwater manager for South Lake Tahoe, each went over the slew of systems in place to keep sediment from reaching this alpine lake. They agree more than 70 percent of the particles clouding the lake comes from the urban environment. Wigart at first said 90 percent of that 70 percent is from roads, with commercial properties the next largest contributor, then residential sites. Then he waffled and said there is no exact breakdown of what makes up the 70-plus percent.

Even so, the bulk of the infrastructure being put in is to treat what is flowing off the roads. This is done through stormwater basins, sweeping the streets – particularly after brine or decomposed granite (a traction substance) has been applied in winter.

It wasn’t until the late 1990s that people started to realize roads are conduits for bringing gunk to the lake. It has been in the last handful of years since the Lahontan Regional Water Quality Control Board put in the total maximum daily load mandate that jurisdictions, state departments of transportation and others started to make road runoff such a priority.

Even to this day no one knows how many outfalls there are into Lake Tahoe. Heyvaert said there are 170 that have been documented. Pipes carrying the dirtiest water are getting filtration systems first.