an increase in flooding downstream an increase in regional humidity a decrease in the amount of river ecosystems a decrease in the amount of water for irrigation
I gave my students this multiple choice question: The construction of Hoover Dam on the Colorado River resulted in abundant freshwater and electrical power for the region. Which of these is a disadvantage of the construction of Hoover Dam?

Only one answer is correct among these 4 choices:
- an increase in flooding downstream
- an increase in regional humidity
- a decrease in the amount of river ecosystems
- a decrease in the amount of water for irrigation

Could you tell me which one is correct?

a decrease in the amount of river ecosystems