Ecological Impacts

A.P. Environmental Science

Freeman

3B

Ecological Impact of the Dam

• Most constructions of dams like the one in the Colorado River negatively impact the functioning of its surrounding ecosystem and aquatic life.

• The decreasing supply and transportation of sediment is a main cause in the degradation of a post-dam’s ecosystem.

• When the dam in the Colorado River was constructed the sediment flow significantly changed and started to build up and became the Lake Powell reservoir.

• The sediments began to be distributed poorly throughout the river due to the low amount of water flow which caused a decline in coarse organic sediment that lead to the extinction of some aquatic species.

• The Colorado squawfish, the roundtail chub, and the bonytail chub have become extinct while other species have become endangered.

The Colorado Squawfish

The Roundtail Chub

The Bonytail Chub

Ecological Impacts of the Dam• Water quality also dramatically changes after the

construction of a dam because of the change in temperature that creates a shift in aquatic population as well as reducing biodiversity.

• The obstruction of free flowing water has impacted the Colorado River so significantly that the Department of Interior has indicated that this river is one of the poorest water qualities in the nation (Ingebretsen, 1998).

• Since the water flow is unable to move freely sediments often pile up on one area and are not circulated throughout the river. Therefore otherwise harmless trace metals and salts such as selenium, arsenic, and mercury can be converted into a detrimental hazard.

Mussels in the Hoover Dam• The Bureau of Reclamation want to use experimental

pesticides to control the invasive species of mussels that are interfering with dam and hydroelectric operations that supply water and electricity to homes.

• Quagga mussels only recently discovered in 2007 are blocking the water lines used to cool the 17 massive hydropower turbines at the Hoover Dam.

• One temporary solution was to have divers spray the mussels with high powered hoses, but the process is only temporary and is expensive.

• The turbines that supply electricity to 1.6 million people in Arizona, California, and Nevada have been temporarily shut down.

• The Bureau Of Reclamation has applied to the U.S. E.P.A. for an exemption waiver that would allow them to use the pesticides.

Mussels in the Hoover Dam Zebra Mussel

Quagga Mussel

Mussels in the Hoover Dam• The waiver is needed because the E.P.A. does not

approve commercial use of pesticides.

• The pesticide contains freshwater bacteria Pseudomonas fluorescens that are the latest tool in the on going battle to control the rapid spread of the zebra and quagga mussels that are causing 5 million a year in damages.

Great Lakes pest moves West• Registering a new pesticide or chemical product must

undergo an extensive researching process along with years of close monitoring and studying.

• But in cases of emergency the Federal Insecticide, Fungicide, and Rodenticide Act allows the federal and state agencies to be exempt from the existing laws.

• The dead bacteria releases a toxin that attacks the mussels’ digestive gland

• The pesticide has a high mortality rate ranging from 90-100%

A Better Alternative• People in favor of biological pesticide use states that it

works more effectively than the chemical commonly used. Chlorine.

• Chlorine interacts with organic compounds in the water to produce disinfection biproducts and carcinogenic substances which harm fish and other organisms.

• Quagga mussels can sense when chlorine has been added to the water and clam up for 14 days, requiring for more chlorine applications.

• The use of pesticides could spare Reclamation and other water management agencies from having to hire divers to spray the mussels as well as it being a more effective way.