From Source to Tap

How to use the Clean Water Act to protect sources of drinking water

Explore the interactive watershed infographic and select images to learn what you can do to protect sources of drinking water

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Infographic

Nonpoint Source Pollution

Section 319 Program

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Agriculture and urban areas contribute pollution to surface and ground water through storm water runoff. Runoff pollution is a type of nonpoint source pollution, or pollution that cannot be attributed to a discrete point or single facility, and therefore isn’t covered by the National Pollutant Discharge Elimination System (NPDES) permit program (see NPDES), which regulates point source pollution. The Clean Water Act Section 319 provides states, territories, and tribes with grant money to implement actions that protect against nonpoint source pollution (NPS).

What can I do to protect sources of drinking water?

Participate in development of state Nonpoint Source Management Program Plans to:

  • Share source water, water quality, pollution, and other watershed information to help states plan for source water protection in Nonpoint Source Management Plans and Watershed-Based Plans
  • Present proposals to states for NPS projects that limit impacts of NPS pollution on downstream drinking water sources

Point Source Pollution

National Pollutant Discharge Elimination System (NPDES)

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These industrial, commercial, and municipal facilities threaten downstream drinking water sources by discharging wastewater with various potentially harmful contaminants into the river. Wastewater is a type of point source pollution, or pollution that enters water from a discrete point.

The Clean Water Act regulates wastewater discharges and other types of point source pollution through the National Pollutant Discharge Elimination System, or NPDES. NPDES permits establish pollutant discharge limits for facilities to allow water bodies to meet state water quality standards (see Water Quality Criteria).

What can I do to protect sources of drinking water?

Participate in development and renewal of NPDES permits to:

  • Encourage states and permit writers to include NPDES effluent limits for pollutants that are regulated as drinking water contaminants under state or federal law or that are otherwise identified as contaminants of concern to drinking water sources
  • Encourage states to adopt numeric water quality criteria (or numeric “translators” for narrative criteria) for each contaminant of concern for every drinking water source
  • Share source water quality information with state NPDES permit writers to assist in analyzing the relationship between discharge effluent limits and source water quality

State Waterbody

Water Quality Criteria

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This river is used for recreation and as a source of drinking water. Under the Clean Water Act, State agencies must specify how each waterbody is used (see Designated Uses) and determine the water quality criteria necessary to protect those uses. Water quality criteria establish the limits for contaminant concentrations in state waters. Water quality criteria may be narrative (e.g., “no toxics in toxic amounts”) or numeric (e.g., 1300 ug/L copper) and may vary by designated use. A water body designated for use as a drinking water source may have water quality criteria sensitive to human consumption.

The Clean Water Act requires states to review, revise (as appropriate), and adopt water quality standards every three years in a process called the Triennial Review of Water Quality Standards.

What can I do to protect sources of drinking water?

Participate in your state water agency’s Triennial Review of Water Quality Standards process or periodic “use attainability analyses” to:

  • Make sure water quality criteria for drinking water designated use covers contaminants of concern to drinking water sources
  • Encourage states to develop and/or adopt robust, protective numeric criteria, or assessment methodologies and numeric “translators” for narrative criteria
  • Come equipped with pertinent, current information

Water Quality
Monitoring

Monitoring, Assessment, and Impaired Waters Listing

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This scientific survey crew is testing the river to determine whether the water is meeting state water quality standards (See Water Quality Criteria) established under the Clean Water Act. States assess surface waters every two years. Waters that do not meet water quality standards are categorized as “Impaired”, and states are required to develop a Total Maximum Daily Load (see TMDL), which sets the maximum amount of a pollutant that a water body can receive and still meet water quality standards.

What can I do to protect sources of drinking water?

Participate in your state’s Triennial Review of Water Quality Standards process and in development of Draft Assessment Methodologies to:

  • Encourage states to prioritize monitoring in waters that are public drinking water supplies
  • Encourage states to use assessment methodologies that include monitoring of contaminants of concern to drinking water
  • Collect and share substantive water quality data for better assessment of source water quality

Public Water Supply

Designated Uses

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This drinking water treatment facility is drawing water from the river to clean and distribute to the community. The Safe Drinking Water Act requires that all community water systems remove certain potentially harmful contaminants from the water before distribution. The Safe Drinking Water Act does not include restrictions on the quality of water before it enters the facility.

The Clean Water Act, however, requires that all state surface water bodies meet certain water quality standards (see Water Quality Criteria) to protect their designated uses (e.g. drinking water supply). Designated uses specific to drinking water are supported by water quality criteria that are designed to protect public health, in consideration of waters that are used as sources of drinking water.

What can I do to protect sources of drinking water?

Petition your state agency or participate in the Triennial Review of Water Quality Standards or periodic “use attainability analyses” to:

  • Encourage states to designate all public drinking water sources for “public water supply;” not all sources of drinking water may currently be designated as such
  • Come equipped with pertinent, current information

Polluted Water Body

Total Maximum Daily Load (TMDL)

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This river segment is polluted. Waste from industry, sewage treatment, and storm water runoff have reduced water quality, and the river no longer serves its designated uses (e.g. public water supply, freshwater fishery) (see Designated Uses). Under the Clean Water Act, a water body that fails to meet the water quality standards (See Water Quality Criteria) necessary to achieve its designated uses is categorized as “Impaired.” States are required to devise and implement a Total Maximum Daily Load (TMDL) to limit pollution and restore the water quality of an impaired water body. TMDLs provide the basis for both point source pollution limits (see NPDES) and nonpoint source control (see Section 319).

What can I do to protect sources of drinking water?

Participate in development of draft TMDLs and draft TMDL Implementation Plans to:

  • Collect and share substantive source water quality information with state Clean Water Act authorities
  • Encourage states to prioritize water quality monitoring of contaminants of concern to public water supplies
  • Encourage specific source water protections in state TMDL Implementation Plans
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