Where does 90% of the water in the Colorado River come from?

About 85–90 percent of the Colorado River's discharge originates in melting snowpack from the Rocky Mountains of Colorado and Wyoming. The three major upper tributaries of the Colorado – the snow-fed Gunnison, Green, and San Juan – alone deliver almost 9 million acre-feet (11 km3) per year to the main stem.



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The three “Lower Basin” states also receive 7.5 million acre-feet. Of that, California has the right to take up to 4.4 million acre-feet from the river each year; because they have the oldest legal rights to the river, Californians are also the last to see cuts during drought.

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What happens if Lake Mead dries up forever? If Lake Mead were to run out of water, the Hoover Dam would no longer be able to generate power or provide water to surrounding cities and farms. The Colorado River would essentially stop flowing, and the Southwest would be in a major water crisis.

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If the water levels dip much lower, the Colorado's northernmost reservoir won't have enough in the tank to both fill Lake Mead downstream and generate any hydropower, which would have devastating effects on the electricity grid in the western US.

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Climate change, a rising population, and unsustainable consumption of water in the southwest are threatening the very existence of the Colorado River that's been running through the center of the Grand Canyon for six million years.

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The Colorado River is a critical resource in the West, because seven basin states (Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming) depend on it for water supply, hydropower production, recreation, fish and wildlife habitat, and other benefits.

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Colorado River crisis is so bad, lakes Mead and Powell are unlikely to refill in our lifetimes. Boaters are dwarfed by a white bathtub ring around Lake Mead.

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Results indicate the Colorado may not be as deep as previously thought. Matt Kaplinski is a geologist at Northern Arizona University and leads the survey project. His data show the median depth of the river is just 25 feet—with the deepest point recorded so far at a little over 87 feet above Phantom Ranch.

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As mentioned, it's possible for the water level in Lake Mead to drop to the point where the dam cannot generate hydroelectric power. However, it's very unlikely that the lake would completely run out of water.

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Key Points. Lake Mead has dropped by 70% due to droughts in the West and it will take many years to refill again, naturally. The reservoir is vitally important to millions of people as a source of water, electricity, and recreation.

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Electricity would not just be the only thing lost. Without Lake Mead, Las Vegas would lose access to 90 percent of its water sources. If Lake Mead were to reach dead pool, it would technically still be able to supply drinking water to Las Vegas. But there will not be enough water for agricultural activities.

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The Colorado River is drying up due to a combination of chronic overuse of water resources and a historic drought. The dry period has lasted more than two decades, spurred by a warming climate primarily due to humans burning fossil fuels.

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Completely surrendering the Colorado River to the free market, as PERC and others suggest, could make water appropriately expensive to use. But it could also reward investors that have snapped up basin farms recently without solving the water crisis, as has been seen in Australia.

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