From Huffpost Green (Brian Fagan):
In 1893, John Wesley Powell of Grand Canyon fame, Director of the US Geological Survey, addressed an irrigation conference in Los Angeles about water in the American West. He flatly stated that there was insufficient water in the American West to support widespread irrigation agriculture. Powell was shouted down, forced by hostile interests in Congress to resign from the Geological Survey. But history has shown he was right, for our reckless consumption has taken us far beyond the point of sustainability…
No question, our grandchildren and great grandchildren will live in a very different hydrological world. Quite apart from renegotiating the now-obsolete Colorado River Compact, we will have to break the habits of our lifetimes and use water very differently. If, for example, we reduced agricultural allocations and the amount of city water going to landscaping from 50% to 5%, we would save nearly 20% of the annual flow of the Colorado River alone.
Groundwater is also vanishing further to the east, from Colorado and New Mexico to Texas, Oklahoma, and Nebraska, where the vast Ogallala aquifer under the Great Plains supports hundreds of communities, also large cities and major agricultural and mining activities. The Ogallala supplies about a third of the nation’s groundwater used for irrigation. US Geological Survey experts have calculated that irrigation alone sucked about 21 million acre feet (260 cubic kilometers) of water from the Ogallala in 2000, a figure slightly larger than the historic annual discharge rate of the Colorado River. Some hydrologists believe that the aquifer will dry up in about 25 years.
More Colorado water coverage here.