What is Source Water
?
Source water is untreated water from streams, rivers, lakes,
or underground aquifers which is used to supply private wells
and public drinking water. Most public and some private well drinking
water is treated before it enters our homes. While some treatment
is usually necessary, the costs of treatment and risks to public
health can be reduced by ensuring that source water is protected
from contamination.
Where Does Drinking Water Come From?
Most source water is defined as surface or ground water. If you
live in a large metropolitan area, the majority of your drinking
water probably originates from a surface source such as a lake,
stream, river or reservoir. The land area that can have an impact
on these water bodies is called a aquifer recharge area, and can
be delineated on a map.
If you live in smaller community or have a private well, it is
more likely that your water originates from underground and is
pumped to the surface through a well. Ground water comes from
natural under ground layers, often of sand or gravel, that contain
water. These formations are called aquifers. The land area that
can have an impact on the quality of this underground water is
called the watershed.
Drinking water suppliers now provide reports (sometimes called
consumer confidence reports that explain where drinking water
comes from, and what contaminants may be in it. You can also view
information about your watershed, groundwater supply, and drinking
water supplier in EPA's database.
What are the Threats to Source Water?
There are many contaminants that may be present in source water
before it is treated.
These include:
- Microbial contaminants, such as viruses and bacteria,
which may come from sewage treatment plants, septic systems,
agricultural livestock operations, and wildlife.
- Inorganic contaminants, such as salts and metals,
which can occure naturally or result from urban stormwater runoff,
industrial or domestic wastewater discharges, oil and gas production,
mining, or farming.
- Pesticides and herbicides, which may come from a variety
of sources such as agriculture, stormwater runoff, and residential
uses.
- Organic chemical contaminants,
including synthetic and volatile organic chemicals, which are
by-products of industrial processes and petroleum production,
and can also come from gas stations, urban stormwater runoff,
and septic systems.
- Radioactive contaminants, which can be naturally occurring
or be the result of oil and gas production and mining activities.
Assessing the Risks
While many states, water systems, and localities have watershed
and wellhead programs , the 1996 Safe Drinking Water Act Amendments
placed a new focus on source water quality. States have been given
access to funding and required to develop Source Water Assessment
Programs (SWAP) to assess the areas serving as public sources
of drinking water in order to identify potential threats and initiate
protection efforts.
The source water assessment programs created by states differ
since they are tailored to each state’s water resources and drinking
water priorities. However, each assessment must include four major
elements:
- delineating (or mapping) the
source water assessment area,
- conducting an inventory of
potential sources of contamination in the delineated area,
- determining the susceptibility
of the water supply to those contamination sources, and
- releasing the results of the
determinations to the public.
These steps are described in more detail in the Source Water
Assessment section of this site. Our SWAP Contact List has state
specific contacts and links to State web sites.
Why Protect It?
Protection of drinking water at the source can be successful
in providing public health protection and reducing the treatment
challenge for public water suppliers. Source water quality can
be threatened by many everyday activities and land uses, ranging
from industrial wastes to the chemicals applied to suburban lawns.
Private well owners are urged to test regularly for common contaminants
such as microbes and nitrate-nitrogen. Water systems are heavily
regulated through the Public Water System Supervision Program,
and must respond to this threat to public health with regular
water quality monitoring and actions ranging from well closure
to expensive treatment. In some cases, source water protection
can eliminate or forestall the need to change or modify treatment
processes. Treatment is expensive and source water protection
can save consumers significant money.
The Source Water Protection section of this site provides more
information about protection programs.
EPA's Focus on Source Water Protection
The 1996 Safe Drinking Water Act Amendments placed a new focus
on source water protection:
States are to implement Source Water Assessment Programs (SWAPs)
to assess areas serving as sources of drinking water in order
to identify potential threats and initiate protection efforts.
Annual Water Quality Reports, produced by water system operators,
provide consumers with information about their source water.
States can fund source water protection activities through the
Safe Drinking Water State Revolving Fund. Source water assessments
and protection measures are eligible uses of the Drinking Water
State Revolving Fund (DWSRF) set-asides. States may use the funds
for a mixture of source water related local assistance activities.
For example, funds are available for Land Acquisition and
Conservation Easements, and Wellhead Protection Programs.
The UIC Program works with Stateand local goverrnments to oversee
underground injection of waste in order to prevent contamination
of drinking water resources.
EPA is working with a broad spectrum of stakeholders to develop
a national strategy for source water contamination prevention.
When it is complete, the strategy will reflect what EPA's Water
Program can do to further source water contamination prevention
nationwide.
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