Clean Water Act (College Board AP® Environmental Science): Study Guide

Clean Water Act (CWA)

Background

• Introduced in response to severe water pollution and public outcry in the mid-20th century

  • Major rivers like the Cuyahoga River in Ohio were so polluted they repeatedly caught fire

  • Widespread contamination of drinking water and aquatic ecosystems from industrial and municipal waste

• The Act aimed to

  • Restore and maintain the chemical, physical, and biological integrity of U.S. waters

  • Set standards for surface water quality

  • Make it illegal to discharge pollutants into navigable waters without a permit

• Focuses on point source pollution — i.e., pollution from a single, identifiable source such as a pipe or drain

Key Dates

• 1972: Clean Water Act passed as a major amendment to the 1948 Federal Water Pollution Control Act

• 1987: Major amendments added to address nonpoint source pollution, including runoff from agriculture and urban areas

How the Clean Water Act relates to the environment

• Regulates pollutants in rivers, lakes, wetlands, and coastal waters

  • Protects ecosystems by limiting toxic discharges from factories, sewage plants, and storm drains

• Requires wastewater treatment before discharge into natural water bodies

  • The Act supports the need for primary, secondary, and tertiary treatment to protect waterways

• The CWA is a solution to impacts like oxygen depletion, bioaccumulation, and ecosystem disruption

• The CWA also supports:

  • Protection of wetlands, essential for water filtration and flood control

  • Reduction of nutrient pollution, which contributes to eutrophication and dead zones

Evaluation

• Successes:

  • Water quality has improved in many U.S. rivers and lakes

  • Sewage treatment is now standard practice, reducing pathogen exposure

  • Helps preserve aquatic biodiversity and improves recreational and drinking water standards

• Challenges:

  • Nonpoint source pollution (e.g. agricultural runoff, urban stormwater) remains a major problem

  • Enforcement gaps and political pressures can limit its effectiveness

  • Wetlands protection has faced legal controversy over what counts as “waters of the United States.”

  • Climate change, increasing rainfall, and urban sprawl are stressing water infrastructure not originally designed for such challenges