Climate Change Daily Earth Science Hydrosphere Repost

The Colorado River is running dry

Historically communities and cities developed along waterways because of the critical need for transportation and water for consumption and agriculture. However, throughout the history of civilizations, people occasionally devised ingenious ways of moving large quantities of water from natural waterways to remote locations, thus bypassing geography. Roman aqueducts are an example of this type of technology. The scale of modern engineering, however, has allowed for water displacement on a grand scale.

The Colorado River flows 1,450 miles from its headwaters in the Rocky Mountains to the Gulf of California. In its natural state, this river delivers about 22,500 cubic feet per second of flow. However, today, waters from the Colorado River are lucky to make it to their final destination in the Gulf of California.  

 The Colorado River provides water for some 40 million people. Also, it provides irrigation for 5.5 million acres, and it provides 4,200 megawatts of hydroelectric power generation capacity. The dams for these hydroelectric power plants and other storage dams hold up to 4 years of average annual river flow and serve as a flow stabilization system. But the demands on this river now exceed its annual flow capacity. 

From 1999 – 2004, Lakes Powell and Mead on the Colorado River (two of the largest reservoirs in the USA) lost half their water. This lost volume represents enough water to sustain Las Vegas for 80 years. 

Water Use

The long-term annual average river flow is 16.4 million acre-feet (MAF). However, demand started seriously exceeding supply at the beginning of the 21st century. In 2009, for example, the yearly supply through precipitation was about 12 MAF, and demand was just under 15 MAF.

Studies (like the “Colorado River Basin Water Supply and Demand Study” from the U.S Department of the Interior Bureau of Reclamation) provide complex scenarios on the future use of the Colorado River. However, the bottom line is that future aspirations look unrealistic under current plans because of projected water demand between 18 and 20 MAF per year, with a projected annual supply of 16 MAF. Almost every state and other water use entity on the river projects increased withdrawals to meet an ever-growing population. However, the planned water supply number may be overstated based on recent investigations of how climate change affects river flow.  

Water flow in the Colorado River has declined by 20 percent compared to the last century. Climate change, particularly in the form of rising global temperatures takes its toll. Snow cover and snowpacks are decreasing. Thus, there is less water stored as ice in the winter to feed the river in the warmer months. Reduced snow cover also produces a feedback loop because the exposed ground absorbs more heat, further melting the adjacent snow cover. 

Warmer temperatures also facilitate more evapotranspiration increasing overall water loss from the system. So, under current conditions, river discharge could shrink another 25 percent by the middle of this century.

The future

Six major cities (Denver, Salt Lake City, Las Vegas, Phoenix, Los Angeles, and San Diego) and 40 million people depend on the Colorado River. Also, this river supports about $1 trillion of economic activity each year.

The current projected demand will exceed available supply in the foreseeable future. The future of cities and agricultural businesses dependent on the river requires solutions that reduce water withdrawals. However, the shape and form of those accommodations remain unknown. 

Water is critical for survival, and much of the American Southwest is now under pressure to find innovative solutions to their water needs; innovations that are sustainable and don’t depend on the Colorado River. Climate change and excessive water withdrawal demands may prove the be the biggest challenge this area will face in the 21st century. 


Sinking ground – Water in the American West (Source: ArcheanWeb) – Also:

Hot and dry in the Western USA, a megadrought in progress (Source: ArcheanWeb) – Also:


About 40 million people get water from the Colorado River. Studies show it’s drying up (By Ian James; USA Today) – Also:

Climate change is drying up the Colorado River, putting millions at risk of ‘severe water shortages’ (By Drew Kann; CNN) – Also:

Colorado River Basin Water Supply and Demand Study (By U.S Department of the Interior Bureau of Reclamation) – Also:

Colorado River flow dwindles as warming-driven loss of reflective snow energizes evaporation (By P. C. D. Milly & K. A. Dunne, Science) – Also:


Feature Image – Colorado River (By Adrille) (Modified) –  – This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. –

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.