Generating electricity using large-scale hydroelectric schemes has both benefits and problems for the environment.

Which row in the table correctly identifies an environmental benefit and an environmental problem associated with hydroelectric dams?

	Environmental Benefit	Environmental Problem
Row A	Flooding of upstream valleys increases land area available for agriculture	Blocks fish migration routes and disrupts downstream aquatic ecosystems
Row B	Provides a renewable source of electricity with zero greenhouse gas emissions during operation	Flooding of reservoirs submerges vegetation, which decays anaerobically to release methane ( $CH_4$ )
Row C	Provides a renewable source of electricity with zero greenhouse gas emissions during operation	Reduces emissions of acid-rain-causing sulfur dioxide ( $SO_2$ ) compared to fossil fuels
Row D	Blocks fish migration routes and disrupts downstream aquatic ecosystems	Provides a renewable source of electricity with zero greenhouse gas emissions during operation

Generating electricity using large-scale hydroelectric schemes has both benefits and problems for the environment.

Which row in the table correctly identifies an environmental benefit and an environmental problem associated with hydroelectric dams?

	Environmental Benefit	Environmental Problem
Row A	Flooding of upstream valleys increases land area available for agriculture	Blocks fish migration routes and disrupts downstream aquatic ecosystems
Row B	Provides a renewable source of electricity with zero greenhouse gas emissions during operation	Flooding of reservoirs submerges vegetation, which decays anaerobically to release methane ( $CH_4$ )
Row C	Provides a renewable source of electricity with zero greenhouse gas emissions during operation	Reduces emissions of acid-rain-causing sulfur dioxide ( $SO_2$ ) compared to fossil fuels
Row D	Blocks fish migration routes and disrupts downstream aquatic ecosystems	Provides a renewable source of electricity with zero greenhouse gas emissions during operation

6.1 Monitoring and maintaining the environment

6.1 Monitoring and maintaining the environment Questions