Lake Tahoe sits right on the state line between California and Nevada, and the two states work together to protect the lake’s ecosystem. The partnership has helped to stall the reduction in the remarkable clarity of the lake’s deep blue waters.

But now Nevada wants out of the partnership if it doesn’t get some concessions from California.

Mark Twain wrote that while fishing in Lake Tahoe he could see the gills on a fish open and close 84 feet down. For a more scientific measure of clarity, the University of California, Davis sends out a research vessel to take readings every 10 days. Biologist Brant Allen explains to boat passengers why clarity matters.

“Well, since you’ve been on the lake, you’ve all seen how beautifully clear Tahoe is and that incredible blue color. The reason we have that is we have this really small watershed compared to the volume of the lake,” Allen says.

A Joint Effort To Keep Tahoe Clean

Tahoe is 22 miles long, 12 miles wide and more than 1,600 feet deep.

To measure clarity, scientists clip a small white disc on to a cable and lower it into the lake until it disappears.

When they started keeping track of clarity back in the 1960s, you could see the disc as far down as 102 feet. Now, Allen says, the readings average only about 70 feet.

“On the current path, the lake was going to continue losing clarity at about 1.2 feet per year,” Allen says.

Fortunately the trend slowed in the last few years. Clarity’s not getting better, but it’s not getting worse. Scientists say that’s partly because California and Nevada started tackling the problem together. With an act of Congress, they created the Tahoe Regional Planning Agency. The agency did something drastic: It imposed a cap on the amount of ground landowners could cover with buildings, says agency spokeswoman Julie Regan.

“It’s almost like a cap-and-trade system for development. If you wanted to build a hotel or a business, you would have to tear one down somewhere else in order to do that,” she says.

Fewer buildings mean less erosion. And that means less dirt and nutrients flowing into the lake to make the water murky.

Nevada’s biggest problem with the TRPA is its voting structure. It takes a supermajority to approve projects; as few as four of the 14 board members can block a development.

There’s a reason those rules are so strict.

Slowed Redevelopment

Looking at the lake from 9,000 feet, Rochelle Nason — of the League to Save Lake Tahoe — points down to a neighborhood called the Tahoe Keys on the south shore in California.

“You are looking at one of the worst things to ever happen to Lake Tahoe,” Nason says.

Before the TRPA existed, developers dug canals so they could build new lakefront property — lots of homes with boat docks. They dug right in the middle of a pristine meadow and marsh, which naturally filtered the main river flowing into Lake Tahoe. Nason points to ribbons of brown water just offshore.

“You see a plume of sediment,” Nason says.

The TRPA put an end to shortsighted projects like the Tahoe Keys. But Nevada says it is also stalling redevelopment.

“We’re all together on not wanting to pollute the lake,” says Roger Wittenberg, who’s building a hotel on the Nevada side. “We’re all together on wanting to see the lake improve, actually. The real debates begin when we talk about ‘how do we go about doing that.‘”

Wittenberg wants to do his part by tearing down an old 1940s casino on the North Shore of Tahoe. He would shrink the casino floor and build a green-certified hotel complex called Boulder Bay. In fact, the new hotel would capture its own runoff water, sending almost none into the lake. To the TRPA board, that makes it an easy sell, right?

“It took four years to go through the process,” he says.

Stories like Wittenberg’s led Nevada to demand relaxed voting standards. If California and Congress don’t agree to the change by 2017 at the latest, Nevada plans to pull out of the TRPA.

That would leave the states to go their separate ways. And that would mean two sets of rules, which many fear would not protect one giant lake.

Copyright 2011 KUNR-FM. To see more, visit http://www.kunr.org/.