Water control on the Colorado River

Major engineering work on the river began around the start of the 20th century.

The main dams in the river basin were built between 1910 and 1970. The Colorado River is now considered among the most controlled in the world, with every drop of its water fully allocated.

High rates of water removal for irrigation and industry combined with declining natural runoff due to climate change, could lead to severe shortages by the mid-21st century, endangering power generation and water supply.

During the construction of Glen Canyon Dam, environmental organisations vowed to block any further development of the river, and a number of later dam and aqueduct proposals were defeated as a result of citizen opposition.

Water is allocated to the states that the river runs through and Mexico, passing through the Colorado River Compact. This compact was originally drafted in the 1920s, based on decades of abnormally high flow.

Lake Mead
Satellite view of Lake Mead

This has resulted in more water being allocated to river users than actually flows through the Colorado. Droughts have exacerbated the issue.

Major reservoirs have dropped to historic lows in recent years, with Lake Powell just one third full in 2005.

Rapid development and economic growth further complicate the issue of a secure water supply.

Although stringent water conservation measures have been implemented, the threat of severe shortages in the Colorado River basin continues to increase each year.

More than a hundred dams have been built by the Bureau of Reclamation and the Army Corps of Engineers for flood control and to create hydroelectricity and store agricultural and municipal water. They harness the river's widely varying flows to generate a steady water supply.

Despite the widespread benefits of reclamation efforts, over-allocation and drought have placed significant stress on reservoirs and water storage.

There are many positive and negative consequences of water control projects on the Colorado River. They can be split into social, economic, political and environmental areas.