When operations on Glen Canyon Dam started in 1955, environmental protection was not an issue. Today, preserving the environment is very important to many people. The decommissioning of Glen Canyon Dam is a very heated debate. Both those opposed and those for the dam have solid arguments. In the end, the values of American society will make the final decision of whether the dam stays or goes. What effect does Water Temperature have on the Colorado River Basin Ecosystem? In its natural state, the Colorado River water is warm and filled with sediments. Fine substrate, cobble and logs pass down the river, giving it a murky appearance. The contents of the stream are very important to the natural environment surrounding the Colorado River Basin. Logs provide an abundant source of carbon, a necessity of all life on earth. They create food and homes for animals and fertilizer for the riparian zone. Once the Colorado River enters Cataract Canyon, it filters into Lake Powell. The previously warm and muddy river becomes part of a deep reservoir with many varying temperatures. The surface level ranges between 75-80 degrees Fahrenheit. This temperature makes the lake appealing for swimming and boating. The middle level ranges from 57-72 degrees Fahrenheit and is the home of many non-native fish such as stripped bass, small-mouth and large-mouth bass, black crappie, sunfish, walleye, threadfin shad, crawdads, carp and trout. The temperature at the bottom level of Lake Powell drops down to 47 degrees Fahrenheit. This level of the lake is uninhibited due to the extremely cold water. The cold water which passes through the penstocks is the start of a totally different Colorado River than was present before Cataract Canyon. The water is now held at a constant. It is always clear and around 47 degrees Fahrenheit. Instead of relying on external energy from the logs, the section of Glen Canyon below the dam relies on internal energy from algae. The algae fields, known as Clodephera, have flourished because of the clear water which allows sunlight to penetrate the surface of the water. Non-native species like Clodephera have created a new food base in the tailwaters area. Clodephera shelter energy rich diatoms which are eaten by small flies called Chironomids which then are eaten by a freshwater crustacean called Gammarus. These tiny flies and crustaceans are the food base for the fish, reptiles and birds at the upper end of the food chain.

What effects do the lack of sediment have on the Tailwaters?

Lake Powell blocks the sediment necessary to the native Colorado River. A new ecosystem has formed below the dam. The surging river still passes through the canyon, but without the heavy load of sediment it previously carried. The sediment created beaches and washed out much of the current riparian zone. Now beaches are being eroded, the riparian zone is flourishing and few nutrients are being transported from upstream.

The Paria River and the Little Colorado River both contribute sediment below the dam. Although extremely fine and silty, the added sediment slightly reverse the river to its previous state. At these intersections, the river returns to its low-light and low-bio-mass environment. The added sediment abrades the existing algae, thus, affecting the food base and food chain. The sandbars and beaches that are created provide for a healthy environment for native fish like the humpback chub.
 
 
 

How are the Native and Non-Native Species effected? The native fish of the Colorado River include the Humpback chub, Razorback sucker, Colorado squawfish, Bonytail chub, Roundtail chub, Flannelmouth sucker, Bluehead sucker and the Speckled dace. Of these listed, the Razorback sucker, Colorado squawfish and the Bonytail chub are rare or extirpated from the area and the Humpback chub is secluded to one section of water in the Lower Colorado River in the Grand Canyon (Aquatic Habitat and Species). Two major causes in decreased native fish populations include:   1.  Modified habitats, modified hydrologic patterns and cold water released from the lower level of the dam. 2.  Increased competition from non-native species. (Terrestrial Habitat and Species) Non-native fish in Lake Powell include the stripped bass, small-mouth and large-mouth bass, clack crappie, sunfish, walleye, threadfin shad, crawdads, carp and trout. These fish exist only in Lake Powell due to the agreeable water temperatures and water quality. Most do not exist above Cataract Canyon or below Glen Canyon Dam. The rainbow and brown trout are the only two located outside of Lake Powell. They were introduced into the Colorado River in the early nineteen hundreds for sport fishing. They flourish in the cold and clear water created below the dam. The Tamarisk is a controversial non-native species. Pre-dam floods wiped out most vegetation along the Colorado River. The construction of the dam gave the Tamarisk and other foliage a foothold in the river valley. Once established, they overtook the area. The Tamarisk has created habitats for a variety of non-native insects, reptiles and birds. The introduction of these species has strikingly increased the bio-diversity below the dam.

How does flow management effect the Lower Colorado River and its ecosystem?

Altering daily flows have a negative effect on downstream habitats. Current flows range from a minimum of 7,000 cfs during the day and 5,000 cfs during the night to a maximum of 25,000 cfs. Dam operations may not exceed these limits. Seasonal highs and lows are considered by dam operators when deciding how much water should be passed through the dam. If high spring runoff is expected then more water is released to avoid spring flooding and a possible dam collapse. If low spring runoff is expected then less water is released and saved for dry months ahead.

Daily flows may not change 8,000cfs, otherwise, downstream habitats would be jeopardized. The river below the dam would rise and fall too fast for its inhabitants to adjust. The river bottom would be exposed, fish would become stranded on exposed streambeds and vegetation near the shore would die.

All of these measurements are recorded from a gage placed at Lee’s Ferry, 12 miles below Glen Canyon Dam. Among other recordings, the gage measures the promised 8.2 maf released to the Lower Basin in the Colorado River Compact of 1922.

How important is Water Quality and what are the effects of recreation on Lake Powell and the Tailwaters?

Once Glen Canyon Dam was built, the Colorado River could no longer flow through the corridor as it previously did. Saline from runoff was passed downstream and flushed through the system, now is collects in Lake Powell. Spring flows bring more water and more runoff. This decreases salinity by diluting the water. The winter flows create a problem. Due to lack of water entering from the Upper Colorado River in the winter there is less circulation in the dam. Saline concentration is high at this time. A high saline concentration decreases the oxygen level in the water creating anaerobic sediment.

Scientists are unsure of the amount of toxic sediment on the bottom of Lake Powell because a lack of funds has prohibited them from carrying out any tests. Tests aside, all agree that the bottom sediment is definitely toxic. The toxic sediment at the bottom of Lake Powell is a result of salinity from runoff and heavy metals from water activities. Dave Wegner reports that petroleum spills equaling the Alaskan Valdez oil spill enter into Lake Powell every year due to watercraft on the lake (link: GCI). However, the majority of that is evaporated into the atmosphere.

Another problem from recreation on Lake Powell is fecal contamination. In the past, many houseboat manufacturers designed waste disposal systems to empty directly into the lake. This is not an environmental friendly approach to waste disposal and has created ecoli problems on some of the beaches. Ecoli is contracted simply by contact with the bacteria and causes extreme illness. Since the lake is fairly stagnant, ecoli can be detected, the beach restricted, and then treated.

Surface pollution on Lake Powell has caused an occurrence of visually unappealing sights. Bath-tub rings are formed when crud on the surface level attaches to rocks. If the water level lowers, a ring of crud is left circling the rocks. Bath-tub rings cause no environmental problems to Lake Powell, other than they are not pleasing to view.

Uncertainties?

Temperature Control Device:

Many people believe that a selective withdrawal structure could be implemented in the dam to control which level the water is drawn for dam operations. Ideally, water would be taken from the warmer levels of the lake through tubes to the Penstocks. It is predicted that this device would raise the temperature of the tailwaters to between 54-59 degrees Fahrenheit. The native aquatic species might retain their original populations, but there are many other factors that complicate this solution.

Many non-native fish exist in the level of the lake that will possibly be targeted. It is likely that some may survive the passage through the turbulent Penstocks. If that happens, the predatory stripped bass may enter the Lower Colorado area and feed on the Humpback chub.

Also, Worling’s disease may enter Glen Canyon. Worling’s disease attacks and destroys the cartilage of young fish, most commonly the rainbow trout. Due to the cold water below the dam, Worling’s disease is not a problem. If the temperature rises to the mid-fifties, then the Lower Colorado River would definitely be susceptible to Worling’s disease and the million dollar fishing industry would come to a halt.

Sediment & Carbon Transfer:

In order for the Lower Colorado River Ecosystem to be returned to its natural state, sediment and carbon must be transported below the dam. Without those two factors the habitats and lifestyles of native species will never be restored. Currently, sediment enters into Cataract Canyon and fills into the reservoir. This has occurred since the dam was constructed. During this span of thirty years, the reservoir has collected sediment and continues to do so. Is it possible that Lake Powell will fill to the top with sediment? Scientists agree that this is an inevitable fact, but disagree on the actual dates. Some say the lake will fill as soon as 100 years and others say it will take 900 years.

Although scientists are sure that toxic sediments exist beneath Lake Powell, they have no actual facts. Pam Hyde, President of the Glen Canyon Institute, thinks it may be better to deal with the problem now because in 50-100 years the problem may be irriversable.

Some experts suggest that sediments be transported from the San Juan River. Although there is a general agreement that this would be successful, the cost of this process is tremendous. Sediment transfer is predicted in the billions, and who is ready to pay the bill?

Native vs. Non-native Survival:

If Glen Canyon were restored today, what would it look like? Many agree that Glen Canyon would merely be a vast stretch of barren mud flats. It is capable for the area to return to the natural ecosystem, but the length of time is unpredictable. Also, which species, native or non-native, will return to the area first? Some say the Russian thistle and the Tamarisk will take over the riparian zone, others disagree and say the natural willows will prevail over the non-natives.

The dam has hurt some species, but others have thrived in this lush environment. The endangered Humpback chub may be better off if the dam were decommissioned and warmer murky water returned, but other endangered species such as Bald eagles and Peregrine falcons thrive in the lush, food abundant environment.
 

Dam Operations: One big question is whether the power provided by the dam will be needed in the future. It is possible that solar power or something else will become an efficient source of power. Also, some question whether the structure of the dam will last much longer. Glen Canyon Dam was constructed in a corridor of porous sandstone. This sandstone acts like a sponge, collecting the water and retaining it. Hundreds of metal rods, seventy-five feet in length, extend into the sandstone corridor for support. Visitors to the lower dam area are required to wear hardhats as protection from the flaking walls of the canyon. Is it possible that the safety of the structure is on the decline? Black Box Science: The main problem surrounding every dam issue is that little is known about pre-dam conditions. Very few people ever had the opportunity to experience Glen Canyon before the dam was built. Little observation was made before the dam, so little is known about what was once there.