March 4 – Mighty Dry

Today’s factismal: Even though the Colorado River drains seven states, it runs dry before it reaches the ocean!

Rivers are among the most interesting things on Earth. They transport sediment from the mountains to the valleys (and sometimes to the ocean), forming broad, fertile flatlands. They irrigate parched areas and drain wet ones. They can be strong enough to scour the ground all the way to the bedrock, or gentle enough to ride down in an inner tube. Rivers move more than 1.7 billion tons of goods every year in the US alone. Hydroelectric facilities on rivers generate more than 250 million megawatt hours of electricity each year, or about 175 times more than solar power. And yet, rivers are running into problems.

Rivers are used by many different groups for many different purposes. Sometimes, as with hydroelectric dams and recreation, those purposes work together to make a better whole. But more often, they work against each other. Farmers want to use the river water to irrigate their crops, but that takes away water from towns that want to use it to drink and industries that need the water to manufacture products.

The Colorado River Basin includes seven states (Image courtesy Bureau of Reclamation)

The Colorado River Basin includes seven states (Image courtesy Bureau of Reclamation)

The Colorado River is a notorious example of what happens when this problem gets too large. It starts on the western side of the Great Divide, up in the mountains of Wyoming and Colorado. There, the melting snow gathers in innumerable little rills, creeks, brooks, and rivulets. These follow the gravity and flow downhill. As they flow, they come together into ever-larger rivers that finally form the Colorado River. All told, more than four and a half cubic miles of water are gathered by the river to flow along its 1,450 mile length.

But more than five cubic miles of water are spoken for along the Colorado River basin. Some of that is only natural; water evaporates from the river as it flows through the Grand Canyon and on into the desert. But much more of that is demand from people. Farmers use water from the river to irrigate some 3.5 million acres of farmland that produces $3.5 billion worth of food every year. Cities, including Los Angeles, Las Vegas, and Phoenix, get the majority of their drinking water from the river; all told, more than six million people rely on the river for their drinking water. As a result, the Colorado River goes from being a roaring cascade of fresh white water in the highlands to an oozing trickle of brackish slime near the border of Mexico.

Not only does this leave people and crops thirsty, but it has an immeasurable effect on the local wildlife. Where the upper reaches of the Gulf of California used to be fresher water that allowed a wide variety of animals and plants to thrive, now it is an expanding marshland where little grows. And the lack of fresh, cool water has allowed the temperatures in the Gulf to rise, leading to plankton blooms which threaten the whales that come to the area to rest before heading up to their summer homes near Alaska.

Today, scientists, politicians, and ordinary citizens are working to develop plans to help save the Colorado and other rivers. If you’d like help, then consider joining a Riverwatch program (or starting your own!):

One thought on “March 4 – Mighty Dry

  1. Pingback: April 2 – Water You Gonna Do? | Little facts about science

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