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.
Superb reporting.
Our infrastructure is not able to sustain storm water runoff during the drought. God help us with the anticipated major storm. It is a mixed blessing.
Gimme,gimme,gimme mo money. The g-d Tahoe demands it.
Fuls, fuls, fuls all you who bow down to this false g-d.
That is some fabulous planning to spend a billion dollars for a storm runoff system that is equipped to only handle a 20 year storm and not the 100 year storm. Of course the lake will lose some clarity but it will be better with more water in it than what the lake looks like now. One thing I always here from the experts is how bad something is going to be but rarely what the positive side of a situation is.
My Dad says we are having a mexican storm headed our way called El Nino. He saw it on t.v.. so it must be true! Right? Tacos falling from the sky? He’s 92 and has has a strange senes of huomour.
If we do have a heavy winter be prepaed beforehand.
Firewood, candles ,matches, good snow shovels ,a full pantry and if you can afford it, a generator to power the house.
Be safe and be happy. Old Long Skiis
Great summary of an information-packed meeting.
Bring it on! Lake clarity will recover and we need to have water wherever we can get it. IMHO
Russell Wigart is the Tahoe Basin Stormwater Coordinator for El Dorado County. While Alan Heyvaert from DRI answered “NO” to the “Is Lake Tahoe ready?” question, Russell Wigart answered “YES”. Although a catastrophic storm could bring unintended consequences in certain areas; from a water quality / lake clarity perspective there have been huge advances and efforts to mitigate urban impacts. Findings were presented on the advanced winter management system in place from strategic plowing to the use of the new advanced decomposed granite traction sand containing minimal ultrafine particulates. The new native traction sand contains 95% less ultrafine particulates, those causing Lake Tahoe’s clarity loss. The County does have world class snow removal and to keep up with new technology demands, aging equipment and dovetailing with strict water quality standards will inevitably require more resources. The concept of hydrologic connectivity was discussed and how the County has implemented water quality / quantity projects in many of these critical areas that flow directly to a stream, river or lake. The County does design all conveyance for the 100 year runoff for large areas as the article points out, though the 100 year storm is always a concern based on the duration. The County strictly adheres to its design standards and drainage manual requirements for sizing infrastructure. The 20 year storm as referenced in the article is correct though the duration is 1 hour, so the design storm as suggested is for water quality purposes only and equates to 1 inch of rainfall that all BMPs are required to infiltrate. The 20 year-1 hour requirement is not a conveyance standard, but a BMP design standard. The TMDL for Lake Tahoe does not have a source apportionment analysis of the 72% (70% in article) of urban causing clarity loss as the article points out, but current pollutant load reduction models (PLRM) indicate that the largest water quality benefits will come from management and maintenance of road systems, then commercial, then residential. There is no exact percentage that the science to date has indicated for these source distribution areas though the common understanding is the road system is the largest source and the easiest to control / maintain. And bottom line it is not cheap… On a large watershed scale, both commercial and residential all contribute to the solution for controlling runoff volume during large infrequent events and will help in the cumulative effort of “Keeping Tahoe Blue”. This overall effort is ongoing and will need to be continually refined and updated based on the best available information and technology including the continual annual maintenance requirements needed to ensure functionality of existing investments and also to comply with regulations and objectives of multiple stakeholders and agencies. Thank you for the article…
Hello:
“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. . .”
While I don’t think all of that “billion dollars” went into ‘stormwater systems’, it is nevertheless disappointing to think that they were engineered for “20 years” out, as some other projects are over-engineered as they ‘overshoot the mark’with designs that include unneeded technical ‘bulk’…
Ongoing should be standards that move urban areas into less pollution (walkable/bikable communities, quality building products that lessen toxic particulates, etc.) as that also diminishes the possibility of long-term damage, regardless of engineering prowess. . .
100+ years ago, the trees were cleared for the Virginia City mines. The Lake was polluted so bad, the aquatic species were killed off. Looks good now. Please, must we live in constant doom and gloom?