In this module, we'll present the Colorado River as a case study to tie together what you've learned earlier modules about Hydrology relevant to the Western US as well as legal and political aspects of water management in the West. In this lecture, I'll provide a geographic and physical overview of the Colorado River Basin. As you can see in this map, well the Colorado River in the lower right here does not compare with the Mississippi and the Columbia River in terms of average flow. It is the largest river system in the Southwestern region of the US and the fifth longest stream of the United States. Located in the Southwestern US the Colorado River Basin covers about 250,000 square miles which is about the size of Texas. The main river extends about 1,450 miles from its headquarters and the Rocky Mountain to the Gulf of California, the river flows from these jagged mountain ranges to impressive Canyons and vast deserts forming the lifeline of water for many of the large cities in the Southwestern US. The spectacular landscape and its long and rich history attracts millions of visitors annually to the region. Eleven National Parks are located within the Colorado River basin with the most famous being the Grand Canyon National Park. Four point five million visitors come to the Grand Canyon alone each year including about 25,000 who boat sections of the Colorado River within the Canyon with its famous whitewater rapids. Nearly all the water in the Colorado River comes from the deep snow pack in the mountain headwaters in Colorado, Utah, and Wyoming. Once the river leaves these headwaters, it flows through mostly arid landscape that receives as little as three inches of precipitation per year. The river provides at least a portion of the water supply for over 30 million people in the US and irrigates more than four million acres of land inside and outside its watershed. Los Angeles, Denver, and Salt Lake City all the sea significant portions of their water from the Colorado River but are located outside the river basin. If you eat salad anywhere in the US in the Winter, you're probably eating lettuce that was grown in California has Imperial Valley. So you are also consuming Colorado River water. Note on this map here the yellow highlights this are urban and agricultural areas outside of the basin that receive Colorado River water. In addition the river serves about 2.3 million people and about 500,000 acres of farmland in Mexico once it crosses the international border. The Colorado River closed southwest from the rocky Mountains across the Colorado Plateau to the Arizona Nevada border and then beds south at Lake Mead towards the Gulf of California. South of the US Mexico border, the Colorado River enters it's River Delta. Before the river expand it fed one of the largest desert Estuaries in the world with species-rich wetland covering 3,000 square miles. Today, the Estuary is only about one percent of its original size and the rivers flow usually stopped about 100 miles from its mouth. The Colorado River basin includes part of seven states of the US Wyoming, Colorado, Utah, New Mexico, Arizona, Nevada, and California as well as two Mexican States Baja California and Sonora. The Colorado River Basin is home to many Indian reservations and other tribal lands as you can see in this map. For water management purposes, the Colorado River Basin is divided into the upper basin and the lower basin as you can see on this next map you can see the upper and the lower basin. The dividing line between the two basins run-through Lee's Ferry an important river crossing points since the mid 1800 just downstream from Lake Powell. These Ferry is the counting point for the basin at which the main allocation of the reverse flow between the upper and the lower basin is measured. The Colorado River it's intensively managed with the flow of water controlled by 15 dams on the main stem of the Colorado River and many more on its tributaries. The Glen Canyon Dam with Lake Powell is the largest dam in reservoir in the upper Colorado River providing important water storage in the upper basin. The main reservoir for the lower Colorado Basin is Lake Mead. Altogether, the reservoirs along the Colorado River can hold approximately four times the annual flow of the river which is an impressive amount of water. Extensive Aqueducts and Canals that were a transport water from the river to fields and cities in cases hundreds of miles beyond the physical watershed. The dams of the Colorado River a critical sources of Hydro-power for the southwestern US generating over 12 billion kilowatt Power of Hydro-power annually and providing more than 30 million residents with at least a portion of their electricity. It is believed that the Colorado River is the most studied dam and litigated river in the US. The management of the Colorado River is challenging with a growing and changing needs of the users including the environment. I hope this overview gave you a sense of the geography of the region and provides the background for details we'll be presenting in this module. You'll first hear about the history of development of the Colorado River Basin. In the next lecture, I will cover the climate and the Colorado River Basin. Then you'll hear about the Colorado River, Water Supply, and demand study and in the final lecture we'll provide an introduction to the Grand Canyon experimental flows. See you next time.
