Hydroelectric Dams and the Environment

In this lesson, students apply their knowledge of water as a natural resource and engineering to determine how the use of dams helps people by controlling the river and providing electricity, but it also has negative impacts on the environment—specifically on native Chinook salmon populations. 

• When water collects on Earth’s surface in lakes, rivers, and ponds, the biosphere interacts with the hydrosphere. 
• Chinook salmon are part of the biosphere, and they live in rivers and the ocean, which are part of the hydrosphere.
• People are also part of the biosphere, and people interact with and influence other Earth systems.
• People can harness the energy in moving water.  
• Dams are a special kind of wall that holds back water. In a hydroelectric dam, the kinetic energy in moving water turns turbines. Those turbines then turn a metal shaft in an electric generator, which is a motor that produces electricity. The use of dams to generate electricity affects the Chinook salmon.
• People use energy resources, but these uses can have an effect on the environment.
  
  

• Why are Chinook salmon part of the biosphere?
• What would happen to salmon without the hydrosphere?
• What parts of the hydrosphere do Chinook salmon live in?
• Why is the journey to the Pacific Ocean and back dangerous?
• How is water similar to fossil fuels, wind, and solar energy?
• Why is hydroelectric power a renewable source of energy?  
• How can dams be used to create electricity from moving water?
• Why is electricity important for people?  

Misconception: The energy that people use does not come from natural resources.

Fact: Energy resources come from the environment, including fossil fuels, wind, water, and solar.

Misconception: Science and engineering are completely separate from each other.

Fact: Science and engineering are interconnected. Engineers use knowledge gained from scientists to design technologies that solve problems. Scientists can then use those technologies to ask deeper questions.

Climate: the average weather over a span of 30 years

Dam: a special type of wall that holds back water, making a reservoir

Flooding: an event that occurs when water overflows onto land that is normally dry

Groundwater:  the supply of fresh water found beneath Earth’s surface in the pores of soil, sand, and rock

Hydroelectric Power: a renewable energy source that comes from moving water

A Dangerous Journey

The journey of the Chinook salmon is dangerous. When the fish first come out of their eggs, they are tiny, barely an inch long. They remain in their stream for about a year as they grow larger.

Many animals hunt the salmon for food in the stream and as they begin their migration down the river. The salmon can become meals for larger fish, birds, and land animals such as bears.

The salmon that survive the journey to the ocean grow large there. Then, they must begin their journey back, swimming upstream against the current. They face predators on this journey as well. A predator is an animal that eats other animals. Animals that get eaten by other animals are called prey.

Damming the River

Another danger facing the salmon is that people have changed the natural flow of the river. This is done with dams. A dam is a special kind of wall that holds back water. Dams slow down the flow of a stream or a river. Because of this, people use dams to control flooding.

They also cause water to pool behind them. This creates a new pond or lake called a reservoir.

How Dams Help People

People also use dams for electricity. Most of the electricity in the northwest United States comes from dams on the rivers. Electricity that comes from moving water is called hydroelectric power. Hydroelectric power is a renewable energy source because it can be replenished in a short period of time.

Remember that moving water has kinetic energy. In a dam, that moving water turns turbines. Those turbines then turn a metal shaft in an electric generator, which is a motor that produces electricity. People use electricity to power lights, electronics, and other appliances.

Protecting Salmon

When fish reach the reservoir of a dam, the river current stops. Without the flow of water, the fish become confused because they lose their sense of direction.

Dams can also be deadly. If a fish is swept into the turning blades of a turbine, it can be killed.

Many commercial fishermen value Chinook salmon and want to help protect the fish. So engineers have designed different technologies to protect the salmon. Most of these technologies, like fish ladders, help the salmon move past the dam so they can continue their journey to the ocean.

In this lesson, students analyze maps and data to determine how Chinook salmon populations have changed over time. Students use the data they gather to explain the possible cause-and-effect relationship between the number of dams on the river and the size of the salmon population.