Protecting Drinking Water

Sources

The 1996 Amendments to the Safe Drinking Water 

Act (SDWA) took a major new step in drinking 

water protection by mandating that states perform 

a source water assessment for each public water 

system. States are responsible 

for completing assessments for 

public water systems in major 

metropolitan areas, small towns, 

schools, restaurants, and other 

public facilities that have a well or 

surface water supply. (Private wells 

are not included in this effort.)

After a state’s Source Water 

Assessment Program (SWAP) 

is approved by the United 

States Environmental Protection 

Agency (US EPA), the state has 

two years, with a possible 18 

months extension, to conduct 

an assessment for each public 

water system and make these 

assessments available to the public. US EPA has 

approved 52 SWAP programs. States must complete 

all the assessments in the state no later than 3 years 

after US EPA approves the programs.

The source water assessment programs established 

by each state differ, depending on the nature and 

threats to the water resources and the drinking water 

program priorities in a particular state. However, 

each assessment program must include four major 

elements:

• delineating (or mapping) the source 

water protection areas 

• conducting an inventory of potential 

sources of contamination in those areas 

• determining the susceptibility of public 

water systems to those contamination 

sources 

• releasing the results of the 

determinations to the public 

Following successful completion of these elements for 

each assessment, communities can use the resulting 

information to identify priority actions for protecting 

their drinking water sources.

Source Water Assessments

The four assessment steps are described in more detail 

below.

Step 1:

Delineate the 

source water 

assessment area

For each 

ground water 

well or surface 

water system 

that supplies 

public drinking 

water, states 

must delineate 

and map the 

boundaries of 

each protection 

area.

For ground water systems, states commonly use 

available information about ground water flow and 

recharge to determine the source water protection 

area around a well or well field.

For surface water systems drawing water from a 

stream, river, lake, or reservoir, the land area in 

the watershed upstream of the intake is identified 

on a map. A topographic map is used to identify 

the perimeter of the area that provides water to the 

water system’s intake. Some states plan to divide the 

watershed area into segments—areas that are closest 

to the intake where most types of contamination 

sources may be found to be significant, and other 

more distant areas. The entire watershed area up to 

the state’s boundaries is required to be delineated 

and mapped, but the level of detail in the inventory 

of potential pollution sources and the susceptibility 

determination can vary in the different segments. 

Coordination across state boundaries is encouraged 

where appropriate.

Step 2: Conduct an inventory of potential sources of 

contamination

In the second step of an assessment, the state 

identifies the potential sources of pollutants that 

could contaminate the water supply. This inventory 

SAFE DRINKING WATER ACT 1974 - 2004 PROTECT OUR HEALTH FROM SOURCE TO TAP
usually results in a list and a map of facilities and 

activities within the delineated area that may release 

contaminants into the underground water supply 

(for wells) or the watershed of the river or lake (for 

surface water sources).

Some examples of the many different types of 

potential pollutant sources include landfills, 

underground or above-ground fuel storage tanks, 

residential or commercial septic systems, urban 

runoff from streets and lawns, farms and other 

entities that apply pesticides and fertilizers, and 

sludge disposal sites.

Step 3: Determine the susceptibility of the water 

supply to contamination

In the third step—the susceptibility determination 

—the state combines the inventory results with other 

relevant information to decide the likelihood of 

contamination of the water supply by the identified 

significant potential sources of contamination. 

This critical step makes the assessments useful for 

communities. It helps local decision-makers consider 

priority approaches for protecting the drinking water 

supply from contamination. Some states prioritize 

the potential for contamination from the specific 

potential contamination sources or to individual 

chemicals that could pollute the water. Other states 

assign a susceptibility ranking of high, medium, or 

low to the water sources.

Step 4: Provide the assessment results to the public

After the state completes the assessment for a 

particular water system, it will summarize the 

information for the public. Such summaries will 

help communities better understand the potential 

threats to their water supplies and identify priority 

needs for protecting the water from contamination. 

This summary information must be included in water 

systems’ Consumer Confidence Reports (annual 

water quality reports). Local communities, working 

in cooperation with local, regional, and state 

agencies, can use the information gathered through 

the assessment process to create a broader source 

water protection program to address current and 

future threats to the quality of their drinking water 

supplies.

Source Water Protection

While source water protection was not specifically 

mandated by SDWA, US EPA and its partners 

encourage states, tribes, and communities to use the 

information from source water assessments to protect 

the delineated source water protection areas from 

identified pollution sources of major concern. Using 

a partnership approach, community groups and local 

officials can plan how to best manage those identified 

potential sources and prevent new contaminant threats 

in the source water area.

Many source water protection areas will include 

multiple jurisdictions, i.e., the city or county where the 

source water intake or wellhead is located, and other 

towns, counties, or states upstream or upgradient from 

the public water system. Local political authorities 

may be able to adopt protection measures within 

their jurisdiction, but to achieve effective protection 

beyond their boundaries, they will usually have to 

work with neighboring jurisdictions or federal or state 

authorities.

Communities use a wide array of different source 

water protection methods to prevent contamination of 

their drinking water supplies. One management option 

involves regulations, such as prohibiting or restricting 

land uses that may release contaminants in critical 

source water protection areas. Along with regulations, 

many communities hold local events and distribute 

information to educate and encourage citizens and 

businesses to recycle used oil, limit their use of 

pesticides, participate in watershed cleanup activities, 

and a multitude of other prevention activities. Another 

aspect of a source water protection program can be 

the purchase of land or the creation of conservation 

easements to serve as a protection zone near the 

drinking water source. For an effective protection 

program, communities should consider using a variety 

of prevention measures.

To assist their efforts to protect areas which surround 

surface water sources of drinking water, local 

authorities can look to Section 303 of the Clean 

Water Act. This section requires each state to review 

its water quality standards every three years. The 

review must consider the “use and value” of the water 

as a drinking water supply. States that adopt water 

quality standards to protect all public water supplies 

and prospective supplies can enforce these standards 

under state and federal law to control pollution.

To augment local ground water protection efforts, 

some states use ground water quality standards that 

work much like the Section 303 program for surface 

water. Some states also use a permit program to 

regulate pollution that can contaminate ground 

water. The federal Underground Injection Control 

(UIC) program regulates the use of wells as a means 

to dispose of waste, and the Resource Conservation 

& Recovery Act (RCRA) regulates the management 

of hazardous and non-hazardous waste that can 

contaminate ground water.

For More Information:

For further information on your state’s source water 

assessment program and how to participate, contact 

the agency in your state that is managing the program. 

Call the Safe Drinking Water Hotline at 1-800-426- 

4791, or visit the safewater web site at www.epa.

gov/ safewate r for more information, state contacts, 

and links to other organizations that may be active 

with source water protection in your area. Your local 

water supplier may also have more information about 

opportunities to become involved in the source water 

assessment process. You can call the phone number on 

your water bill or contact your local health department 

for information on your water supplier.

Office of Water (4606) www.epa.gov/safewater EPA 816-F-04-032 June 2004