How much of Earth's water is unavailable for humans to consume due to its high salinity? 

• 3%
• 23%
• 77%
• 97%

A distinct location from which pollution is directly produced.

• Point source
• nonpoint source
• wastewater
• water pollution

Many areas such as an entire farming region, a suburban community with many lawns and septic systems or storm runoff from parking lots.

• Point source

• nonpoint source

• wastewater

• water pollution

When there is a single identifiable and localized source of water pollution, such as wastewater discharge into a stream.

• runoff
• drainage
• point source pollution
• non-point source pollution

Water pollution that comes from many sources is considered...

• point source pollution

• nonpoint source pollution

• thermal pollution

• ocean pollution

Which would a scientist expect to find in a lake that experienced a sudden increase in nitrate levels?

• an increase in temperature
• an increased number of fish
• an increase in dissolved oxygen
• an increased amount of algae and aquatic plants

Which best explains the importance of pH in determining the health of a water system?

• Most organisms living in water are able to adapt to changing water pH.
• Variations in the pH of water can indicate the presence of toxicsubstances.
• A low pH in ground water encourages the growth of photosyntheticorganisms.
• Variations in the pH of water can affect the ability of water to absorbatmospheric gases.

Which most likely makes fish excellent indicators of watershed health?

• Fish live only for a short period of time.
• Fish live in the water for at least a portion of their life.
• Fish differ in their tolerance to amount and types of pollution.
• Fish are frequently moving throughout different columns of water.

Why is it important to monitor turbidity levels of a water system?

• Frogs will destroy fish eggs in murky water.
• Fish are better able to find food in cloudy water.
• Water can only be used for recreation when it is clear.
• Suspended particles diffuse sunlight and absorb too much heat.

The local middle school has a fish pond in the courtyard. The pond water is suffering from eutrophication. Which most likely caused this problem?

• poor filtration
• direct sunlight
• fertilizer runoff
• improper cleaning