Colorado River Basin Map (image) University of Texas at Austin Share Print E-Mail Caption The Colorado River Basin is divided into upper and lower portions. It provides water to the Colorado River, a water source that serves 40 million people over seven states in the southwestern United States. Credit Colorado River Commission of Nevada Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.