Source: TOI
Subject: Mapping
Context: A new study by the University of Washington has explained why billions of litres of water from the Colorado River are disappearing before reaching major reservoirs like Lake Mead and Lake Powell.
About The Colorado River:
What it is?
- The Colorado River is a 1,450-mile-long (2,330 km) river known as the Lifeblood of the American Southwest. It is the principal freshwater artery for one of the most arid regions in North America, supplying water for municipal use, hydropower, and irrigation to 40 million people.
Located in:
- Origin: The river originates at the Continental Divide at La Poudre Pass in Rocky Mountain National Park, Colorado, at an elevation of 10,000 feet.
- Location: It occupies an area of approximately 250,000 square miles across seven U.S. states and two Mexican states.
States and Regions It Flows Through:
- Upper Basin States: Colorado, New Mexico, Utah, and Wyoming.
- Lower Basin States: Arizona, California, and Nevada.
- International: It flows into northwestern Mexico through the Sonoran Desert before reaching its mouth at the Gulf of California.
Tributaries:
- Upper Basin: The Green (its largest tributary), Gunnison, San Juan, Dolores, and Roaring Fork rivers.
- Lower Basin: The Gila, Little Colorado, Virgin, and Bill Williams rivers.
Key Features of the River
- Grand Canyon: The river is the primary architect of the Grand Canyon, having carved its path through millions of years of geological layers.
- Horseshoe Bend: A world-famous entrenched meander near Page, Arizona, where the river makes a 270-degree turn in a 1,000-foot-deep canyon.
- Major Reservoirs: Home to Lake Mead (formed by Hoover Dam) and Lake Powell (formed by Glen Canyon Dam), the two largest man-made reservoirs in the U.S..
- The Law of the River: A complex collection of compacts, federal laws, and treaties (notably the 1922 Colorado River Compact) that govern its water allocation.
Why the Water is Vanishing?
Recent scientific breakthroughs have shifted the blame from simple evaporation to a complex ecological siphoning effect:
- Aridification: Rising temperatures are permanently reducing flows through a transition from drought to a state of chronic dryness.
- Biological Pumps: Warmer, drier springs cause mountain vegetation (from wildflowers to high-elevation forests) to wake up earlier and draw moisture directly from the melting snowpack before it can reach the river.
- Clear Sky Effect: Clearer skies and increased solar radiation enhance the thirst of plants, which use snowmelt as a primary food and cooling supply.
- Vapour Pressure Deficit: A warmer atmosphere pulls even more moisture from the soil and snow, leaving only 50% of anticipated runoff even when snowpack is at 100% of normal.
