Interior Secretary Dirk Kempthorne, right, and Rep. Jon Porter, R-Nev., walk Tuesday on a houseboat at Lake Mead. Photo by John Locher.

As Western water managers work toward new rules on how to share shortages on the Colorado River, progress also is being made on a similar agreement with Mexico, Interior Secretary Dirk Kempthorne said Tuesday from a houseboat on Lake Mead.

During his first official visit to Southern Nevada, Kempthorne said he is confident that so-called shortage criteria for the Colorado will be finished by the end of 2007, the deadline set by former Interior Secretary Gale Norton.

Also by then, Kempthorne said, he is "hopeful" that an international agreement will be in place to determine Mexico's share of any shortage that might be declared on the drought-stricken river.

Kempthorne was in Las Vegas Monday night to meet for the first time with representatives from Nevada and the six other states that share the Colorado River.

He said talks among the states remain "spirited," but he can tell that water managers are committed to working together to find new strategies for dry years.

"If neighbors can resolve issues, that's far better than leaving it up to someone from another jurisdiction," said Kempthorne, who was sworn in as Norton's replacement on May 26. "These are not easy issues."

The Las Vegas Valley gets about 90 percent of its drinking water from the Colorado River, which is suffering through its worst drought on record.

Southern Nevada Water Authority General Manager Pat Mulroy said representatives from the seven states spent the past two days in closed-door meetings to decide "the nitty-gritty" of various agreements on shortages and the future operation of Lake Mead and Lake Powell.

Monday night's meeting with Kempthorne was more about "getting to know each other," she said.

"It's always difficult in the middle of a process to get a new secretary. There's always a bit of anxiety."

Tuesday marked Kempthorne's first visit to Lake Mead. As the former Idaho governor and U.S. senator looked out at the chalky "bathtub ring" that marks a 90-foot plunge in the lake's water level since 1998, he said the view illustrated "that water is finite" and must be treated with "continued stewardship and best practices."

His comments came during a joint news conference at Lake Mead with Rep. Jon Porter, R-Nev., who was there to tout legislation he introduced last year to ease the removal of non-native tamarisk and other invasive plants from around the reservoir.

Porter was greeted after the event by a half-dozen sign-waving protestors with ties to Tessa Hafen, the congressman's Democratic challenger. Among them was Hafen's media director, David Cherry, who accused Porter of staging a "taxpayer-funded photo op the week before the election" to mask his "bad record on the environment."

Kempthorne's press secretary, Shane Wolfe, said the timing of the Lake Mead event was a coincidence.

The Cabinet member was at the lake to support pending legislation on invasive plants, not to "stump for Congressman Porter," Wolfe said.