The Natural Resources Defense Council (NRDC) on Thursday warned that using water from the Colorado River Basin to produce oil shale could impact agricultural and municipal water uses affecting 15% of the nation's crops and up to 30 million people from Wyoming to Southern California.

The 42-page report explores some of the possible implications of committing a "relatively modest but critical portion" of the Colorado River Basin's water supply to develop potential sources of energy that the authors contend would be "economically and environmentally costly." The Colorado River is a major source of water supply for states in the Colorado River Basin: Arizona, California, Colorado, Utah, Nevada, New Mexico and Wyoming.

In conjunction with climate change, which NRDC scientists estimate could reduce the basins' water supply by 9-25% by 2050, "new oil shale development would further strain future supplies that already are under pressure from current water uses and ongoing growth in urban areas," stated the report, "Between a Rock and a Dry Place: The Impact of Oil Shale Development and Climate Change on the Colorado River Basin Water Supply."

"The Colorado River -- a critical source of water supply for millions of people -- has become a house of cards as water use in recent years has exceeded what the basin provides," said NRDC senior scientist Monty Schmitt. "If oil shale development moves forward, it will compete with farms and cities in the West for limited water supplies that will become scarcer because of climate change.

"The time is now for the Bureau of Reclamation and Colorado River Basin states to tackle this challenge head on, through effective planning, water smart energy policies and dramatic investments in water use efficiency -- the reliable water supply of the future."

According to the NRDC, producing oil from shale rock requires an estimated three to five barrels of water for each barrel of oil produced.

"A new oil shale industry producing 1.55 million b/d of oil would require a projected 360,000 acre-feet of water a year -- the equivalent to one and a half times the city of Denver's annual water use," said Schmitt. "This is a 'mid-range' estimate of potential water use by oil shale development; high-end estimates of oil shale development could require more than a million acre-feet of water -- more than four times Denver's annual water use."

The agriculture industry could be the "most severely affected" by future oil shale development because "more than half of the water flowing in the Colorado River and its tributaries is used for irrigation," the NRDC said. "In Colorado, energy companies own senior water rights that could significantly reduce the water available for that state's agricultural production if oil shale development moves forward...However, the potential impacts could reach other states and Western cities as well."

"Agricultural water users today can reduce water consumption during droughts by increasing irrigation efficiency, changing crops or irrigating fewer acres," the NRDC report stated. "Turning flexible agricultural water use into inflexible industrial use could increase basin-wide conflicts by reducing water supply to lower basin states, particularly Arizona, making it more difficult to develop a basin-wide strategy to live within the long-term supply provided by the Colorado River."

Oil shale development would contribute to climate change, the report stated, because "oil shale production and refining results in appreciably greater greenhouse gas emissions than conventional oil fuels. Well-to-wheel greenhouse gas emission estimates for oil shale show it to have 23-73% greater emissions in comparison to diesel."

The Bureau of Reclamation currently is preparing a Colorado River Basin water supply and demand study, which the NRDC said "should incorporate the potential state and basin-wide impacts of oil shale development and identify management options to meet future water needs."

However, the NRDC is advocating that oil shale development ultimately be prohibited.

"Based on current information and existing technologies, proceeding with oil shale development would be inadvisable given significant impacts to water resources and the environment, including increased greenhouse gas emissions. Any further exploration should begin with an analysis of potential impacts to water users, groundwater and sensitive protected species."

Last year Boulder, CO-based Western Resource Advocates (WRA), an environmental law and policy organization, released a similar report, "Water on the Rocks," which projected water requirements for oil shale development in Colorado. The WRA's report cataloged Colorado water rights that had been acquired by oil shale interests.