An agreement signed Thursday to help the seven Colorado River states cope with drought is historic, says the director of the Upper Colorado River Commission.

Don Ostler, whose four-state commission is based in Salt Lake City, was present in Las Vegas to see the agreement signed by Interior Secretary Dirk Kempthorne and representatives of all states in the Colorado River Compact. The compact apportions water among the seven states using the river: Utah, Arizona, California, Colorado, Nevada, New Mexico and Wyoming.

"It's without a doubt the most significant agreement on the Colorado River since the original agreement (the Colorado River Compact) was signed ... in 1922," Ostler said.

Adjustments have been made to the agreement in the past 85 years, but they weren't as significant as this, he said. "So yes, it's been a historic, exciting" time.

According to the U.S. Bureau of Reclamation, the agreement provides that:

• Specific water levels of Lake Mead, which is in Nevada and Arizona, will be used to determine when a shortage is declared for the Lower Basin states — Arizona, California and Nevada. By shortage, the agreement means less than 7.5 million acre-feet available for those states.

• Reservoir conditions in Lake Powell (Utah and Arizona) and Lake Mead will determine the operation of the two reservoirs. Those operations, according to a press release, are intended to "minimize shortages in the Lower Basin and avoid the risk of water delivery curtailments in the Upper Basin."

• A mechanism will be set up to encourage and account for augmenting and conserving water supplies in Lake Mead to "minimize the likelihood and severity of potential future water shortages and to provide additional flexibility to meet water use needs, particularly under low reservoir conditions."

• Interim surplus guidelines established in 2001 are "modified and extended through 2026."

In prepared comments released by the Interior Department, Kempthorne said drought conditions in America and around the world threaten to worsen. "Here in the West, for example, runoff in five of the seven Colorado River Basin states is projected to decline by more than 15 percent during the 21st century."

If the region becomes warmer and evaporation increases, "we could face a situation in which the amount of precipitation we are receiving today produces significantly less runoff in the future."

The department secretary said he was impressed by the conservation measures, such as the agreement that allows water users to obtain future credit for conserving water and leaving it in Lake Mead. "It also sets up a framework to allow cities to contract with willing farmers to temporarily fallow fields in dry years while respecting the basin's agricultural heritage," he said.