Salinity levels in the Colorado River have increased dramatically during the past century, both from natural sources such as surface erosion and saline springs, and from industrial and municipal sources. Since the Colorado provides water for more than 22 million people and 1.7 million acres of irrigation, salinity levels are a primary issue and have caused environmental problems for the United States and Mexico.
Stanley Schumm, a geomorphologist at Colorado State University, Fort Collins, has studied the Colorado River basin for the past 20 years and has shown that the Colorado and other streams in the southwest are recovering from a period of climatic fluctuations, human activities and grazing practices in the late 1800s that caused accelerated erosion and deep channel incision. Channel incision allowed large amounts of sediment to be deposited in the Colorado from its tributaries. Gradually, the tributary channels widened, stabilized, and formed new floodplains.