Colorado River

Colorado River

April Gonzales

ENV 300: Environmental Biology

Jeanne Lambert

June 18, 2012

Colorado River

        Mother Nature is not in control of the Colorado River any longer, it is now under the control of man to provide water and hydroelectricity to humans in the West.  The damming of the Colorado River has changed the river ecosystem immensely.  The biodiversity, soil content, energy flow, and habitats have all been altered by humans.  These disruptions have resulted in some species becoming endangered and extinct.  There is one positive aspect of the many dams that have been built and that is the clean production of energy that provides electricity, hydroelectric power.

        The Colorado River is a large river that flows through five states in the United States and two states in Mexico.  It starts in Colorado, moves through Utah, Arizona, Nevada, and California, then heads into Baja California and Sonora, and empties into the Gulf of California.  The river runs through a variety of ecosystems ranging from the forests in the Rocky Mountains to the arid deserts of Arizona and Utah.  The northern most dam is Glen Canyon Dam in Arizona, which forms Lake Powell.  Then the river flows south through the Grand Canyon and into Lake Mead which is formed by the Hoover Dam, then flows into Lake Mohave which is formed by Davis Dam.  As the river continues to flow south it feeds into Lake Havasu which is created by the Parker Dam.  Then it runs into the Headgate Rock Dam, Palo Verde Diversion Dam, Senator Wash Dam, Imperial Dam, Laguna Dam, and finally the Morales Dam.  The dams store the Rocky Mountains snowmelt and make it available during the summer months by moving it through pipelines and aqueducts (Kaufmann & Cleveland, 2008).  These waterways are now all controlled in order to provide millions of people with water all year long and to create hydroelectric power in the West.  

        Hydroelectric energy is one of the cleaner options in producing electricity.  Hydropower is defined as the production of electricity by the action of moving water falling on a turbine generator.  Water builds up behind the dam accumulating potential energy.  As it’s released, the falling water rushes through turbines which rotate and spin electromagnets, which in turn create current.  It’s estimated that approximately 20 percent of the world’s electricity and 12 percent of the U.S.’s electricity is generated by hydropower (Kaufmann & Cleveland, 2008).

        Before the dams were built, floods caused the river to overflow and create several temporary lakes, including the Salton Sea.  These temporary lakes would be heavily populated with mullet fish that would end up being stranded and eventually die as the lake slowly evaporated.  Prior to constructing the dam, the flow of the river varied a great deal depending on the time of year and the weather conditions.  Once the dam was constructed and started holding back the water, the flow slowed down and the water temperature decreased, which changed the biodiversity, soil content, and the energy flow.  The natural habitats were disrupted and if the organisms were not able to evolve, then their populations slowly decreased in numbers until they were either endangered or extinct.  The fish that inhabited the river prior to the dams were very unique and couldn’t be found anywhere else in the world.  There were nine native species that called the lower Colorado River home, which include the Razorback Sucker, the Flannelmouth Sucker, the Bonytail, the Humpback Chub, the Roundtail Chub, the Colorado Pikeminnow, the Desert Pupfish, the Sonoran Topminnow, and the Striped mullet. These nine species evolved over millions of years and were able to survive the harsh and extreme conditions of the river that very few fish could tolerate from floods to droughts, extreme temperatures, and high salinity levels (Mueller & Marsh, 2002).  “More than 70 nonnative fish species have been introduced.  Half of these species have established and spread throughout much of the river basin and have virtually eliminated native fish” according to Mueller and Marsh (2002).  Over the years, many species have been introduced to the river including bullhead and channel catfish, common carp, largemouth bass, trout, and sunfish.  There has been a huge loss in habitats in the southern portion of the river, specifically where the wetlands have disappeared.  It is somewhat unknown how the floods played such an integral part of the native fish population.  Perhaps surviving the floods and drought produced much heartier species.  Much of the river today consists of a nonnative trout fishery that normally is found in high mountain areas, not within a desert region.  According to Cunningham and Cunningham (2009), the building of dams “floods vital stream habitats under deep reservoirs and eliminates food sources and breeding habitats for some aquatic species.”  This helps to explain the disappearance of many of the native species.

During the summer months, the water temperatures on the surfaces of the lakes rise causing much more evaporation to occur than when the river ran freely.  The increased evaporation allows more concentrations of salt to be left behind which alters the salinity levels of the water.  Certain areas with bad drainage around the rivers and lakes tend to get crusty from the salt, which contributes even more to the salinity levels when the waters rise again.  The deep lakes tend to have cold and dense water which sinks to the bottom and creates separate layers of water which don’t mix.  As water is released from the dam it comes from the bottom of the lake were it is the coldest water.  According to Mark R. Vinson (2001), studies have shown that “changes in physical habitat, most often water temperature, are primarily responsible for the decline in invertebrate biodiversity that normally follows dam construction.”  This also helps to explain the disappearance of some of the native species.

According to several explorers back in the mid 1800’s (Minckley, et al., 2003), the base of the river was several miles wide and was covered with willow, cottonwood, and mesquite.  The water level was the highest in June and July and the banks were generally flooded.  Because the water flow was so rapid, the islands, sandbars, and channels were constantly changing which made it very difficult to navigate thorough in boats as the explorers made trip after trip up the river.  After the damming, the river is so heavily diverted that it doesn’t reach the ocean unless there is a major flood (Mueller & Marsh, 2002).  Much of the active parts of the river extended to almost two miles wide but now rarely gets wider than 150 yards.  Only parts of the lakes that have been created are wider than the two mile width of the old river, some areas are as much as ten miles wide.  The willow, cottonwood, and mesquite species are long gone.  They used to rely on the floods in order to regenerate.  Some of these plants were cut down and used for firewood and timber and some of it was cleared in order to make room for agriculture.  But most of the plants have died because of the changes in the water table and also because of the very invasive salt cedar trees and arrow weed that have taken over the area.  “Today, only 150,000 of an estimated 1,930,000 acres of wetlands remain” which is only 7.7% of what they used to be (Mueller & Marsh, 2002).