This story is part of a special National Geographic News series on global water issues. 

The early spring of 2012 raised both temperatures and eyebrows, including President Obama's. 

As reported in The Weekly Standard and elsewhere, the President recently commented at an Atlanta fundraiser: "When it is 75 degrees in Chicago in the beginning of March, you start thinking.  On the other hand, I really have enjoyed nice weather."  Now, in April, we're seeing that this spring break may leave us with a fierce hangover. 

On April 10th, 61 percent of the lower 48 states were listed by the U.S. Drought Monitor to be in abnormally dry or drought conditions.  And the Southwest, which largely relies on ice melt into the Colorado River Basin from the Rocky Mountains and previous years' melt stored in the Lake Powell and Lake Mead reservoirs for its water supply, is poised for a dry, hot summer, because those areas received less than 70 percent of the average snowfall according to the USDA National Water & Climate Center. 

These reservoirs are already at only 64 percent capacity following a decade-long drought from 2000 to 2010.  And the possibility of more drought years to come is raising concerns over how to manage a river of which every drop (and then some) is now allocated to some use. 

Drought, however, may be only one factor in the drying up of the Colorado River Basin.  To assess the vulnerabilities of the watershed and consider how water supply and demand might change in the coming years, the U.S. Department of the Interior's Bureau of Reclamation has embarked on a study of the Colorado River Basin to be released this July.  An interim report shows that current water use outstrips the supply and projected demand for water could be greater than the projected supply by more than 3.5 million acre-feet within 50 years, particularly when the effects of climate change are included. 

Water supplies are measured in acre-feet, with one acre-foot equal to the amount of water it takes to cover one acre in a foot of water (325,851 gallons).  So 3.5 million acre-feet of water is a large amount--the Lake Powell reservoir (the second largest in the United States) holds 26 million acre-feet when full. 

Revisiting Supply and Demand

"Existing demand very clearly outstrips existing supply," says Barry Nelson, a senior policy analyst in the water program at the environmental nonprofit Natural Resources Defense Council (NRDC). " That's the main reason we're seeing declining storage.  That simply cannot continue." 

Climate change, meanwhile, poses a threat of increased drought in a region with a long paleo-climatological record of natural drought.  In a 2010 report on the county-level effects of climate change on U.S. water supplies, an analysis by consulting firm Tetra Tech and NRDC projected that by 2050, 27 out of 64 counties in Colorado will face high or extreme risks of water shortages, as well as 13 out of 29 in Utah, 19 out of 33 in New Mexico, 36 out of 58 in California, and a startling 13 out of 15 in Arizona. 

With droughts come wildfires.  As reported in the Denver Post, a weekend snowstorm on April 14 and 15 reduced the immediate risk of fire in the Denver area, but a March 26 fire in the Lower North Fork region of southeast Colorado killed three people, destroyed 27 homes, and blazed through 4,000 acres.  Furthermore, the erosion resulting from wildfires can wreak unexpected havoc upon water supplies. 

In May 1996, the Buffalo Creek fire burned 11,900 acres within the watershed of the South Platte River, a major source of Denver's municipal water.  Two months later, heavy rains washed tons of sediment into the Strontia Springs Reservoir, which holds approximately 80 percent of Denver's water supply.  In one day, the reservoir lost 30 years of its 50-year lifespan. 

Climate change may also mean that less water will fall as snow to be retained in snowpack, and will run off instead as rainwater.  In March, the USDA's National Water & Climate Center announced that the Lower Colorado River basin, along with many parts of the West, was reporting snowpack conditions that were "much below average."  Sandra Postel, National Geographic's Freshwater Fellow, notes, "Climate models estimate that the snowpack that feeds the Colorado River could decline by 30 percent by 2050." 

Seeking Solutions

But there are some encouraging trends.  Most cities that rely on the Colorado River Basin for water have seen their per capita water consumption decline by about 1 percent per year since 1990, according to a 2011 report by the nonprofit Pacific Institute, an advocacy organization devoted to water issues. ( PI also works on climate, community development, etc.) 

Although municipal use accounts for only 15 percent of total consumption of the Colorado River--agriculture dominates by far with a 70 percent share--the rapid rise in population by approximately 10 million people from 1990 to 2008 makes cities the fastest growing consumer.  Furthermore, California in 2009 passed legislation requiring a 20 percent reduction in water use by 2020, which amounts to 2 percent per year, doubling the current rate of decline. 

In Colorado itself, "drought is one of the biggest drivers that we see as potentially contributing to water supply shortage," says Veva Deheza, manager of the Office of Water Conservation and Drought Planning at the Colorado Water Conservation Board.  Rather than aim at specific targets or create a statewide goal, Deheza says, Colorado is taking a multi-pronged approach that includes conservation and efficiency, building new water supply, perhaps transferring that supply from the agricultural sector to the municipal sector, and looking at reuse more aggressively as a potential water supply for the future. 

Yet fragmented state-level responses may pose challenges.  An April report by NRDC analyzed U.S. states' readiness for the impact of climate change on its water resources and found that while the states of Colorado and California had both made plans to prepare for climate change impacts, their neighbors had a long way to go.  According to the report, the state of Utah has made no formal attempt to prepare for the effects of climate change, while Nevada, Arizona, and New Mexico have made only limited efforts.