The Colorado: a Stressed Exotic River Collected and Organized by: Joe Naumann, UMSL

An extremely helpful resource: Physical Environment: An Introduction to Physical Geography By Michael Ritter

Exotic River An exotic stream is one whose headwaters lie in a humid region, and flows through an arid environment Examples: Nile River Colorado River

Colorado River Watershed D E S E R T M O U N T A I N S

HEADWATERS The Colorado River's headwaters are located high in Rocky Mountain National Park, just west of the Continental Divide. After leaving Rocky Mountain National Park the river follows the Kewuneeche Valley and is then dammed to create Grand Lake and Shadow Mountain Reservoir.

Headwaters in the Rockies

The Colorado River as a babbling brook

LOWER COURSE The lower course of the river, which forms the border between Baja California and Sonora, is essentially a trickle or a dry stream today due to use of the river as Imperial Valley's irrigation source. Prior to the mid 20th century, the Colorado River Delta provided a rich estuarine marshland that is now essentially desiccated, but nonetheless is an important ecological resource.

Problem of Reduced Flow & Desiccated Delta Region Recent years of reduced annual snowfall in the Rocky Mountains (could this be related to global warming?) Increasing demand for water by growing cities in California, Nevada, Utah, Colorado, & Arizona Increasing demand for water for irrigated agriculture

Pictorial Evidence of Human Impact on the River Basin

Years of drought in the Rocky Mountains with Forest & Grassland Fires

Colorado Cattleman with a Dry Pond – Result of Drought

A farmer who planted sorghum – drought victim on a field that was not irrigated in Wiggins, Colorado

USA’s fastest growing city, Las Vegas, had doubled its water use –

Both sides of Marble Canyon are very dry

The “Bathtub Ring” around Lake Mead – 2004 water was at a near record low.

For most of Lake Mead’s history, this had been a shallow part of the lake – 2005 photo. The drop that caused the “bathtub ring” caused this too.

This is where the Dirty Devil River flows into Lake Powell before & after the 2002 drought

Colorado River Downstream from the Glen Canyon Dam

Original Delta Conditions Prior to the construction of major dams along its route, the Colorado River fed one of the largest desert estuaries in the world. Spread across the northernmost end of the Gulf of California, the Colorado River delta’s vast riparian, freshwater, brackish, and tidal wetlands once covered 1,930,000 acres

Current Delta Conditions Today, conditions in the delta have changed. Like other desert river deltas, such as the Nile Delta and the Indus River, the Colorado River delta has been greatly altered by human activity. Decades of dam construction and water diversions in the United States has reduced the delta to a remnant system of small wetlands and brackish mudflats. As reservoirs filled behind dams and captured floodwaters, freshwater flows no longer reached the delta.

Colorado Delta in 2004