What is a Source Water Assessment?

Source water is water from rivers, streams, reservoirs, and aquifers that is treated and used for drinking water purposes.  A source water assessment is a process for evaluating a public water system’s source water and assessing its vulnerability to contamination.   The assessment does not address the treatment processes, or the storage and distribution aspects of the water system, which are covered under separate provisions of the Safe Drinking Water Act.  A source water protection program is intended to add an extra layer of protection by ensuring that the water entering a public water system is as safe as possible.  Preventing contamination at the drinking water source protects public health and makes good economic sense.

What Is Maryland's Source Water Assessment Program?

The 1996 Safe Drinking Water Act Amendments required states to develop and implement source water assessment programs for all public drinking water systems. States were required to develop these programs with public input and to submit descriptions of their programs to the federal Environmental Protection Agency (EPA) by February 1999.  In their submittals, each state outlined methods for defining and evaluating risks to each public drinking water system.  The EPA approved Maryland’s Plan in November 1999.

Under the Safe Drinking Water Act requirement, states must evaluate all public water system sources.  Maryland has about than 3,653 public water systems.  There are three major categories of public water systems: community systems, nontransient noncommunity systems, and transient noncommunity systems.  Community systems are water systems that serve 25 or more year-round residents, such as systems owned and operated by municipalities, counties, nursing homes, and trailer parks.  The two largest community systems in Maryland serve the metropolitan Baltimore and Washington areas, providing water for approximately 60% of the State’s population.  Nontransient noncommunity systems serve 25 or more of the same individuals for at least 6 months per year.  Nontransient noncommunity systems include such facilities as schools and places of employment that use their own wells.  A transient noncommunity system serves 25 or more people daily, but not the same people everyday.  Restaurants, convenience stores, and campgrounds with their own wells are typical transient noncommunity water systems.  Domestic wells serving individual homes are not included in this program.

What is the Status of Source Water Assessment in Maryland?

As of March 31, 2006, Maryland has completed source water assessments for all public water systems in the State.  Source water assessment reports have been provided to water suppliers and local governments, and have been made available to the public through placement in public libraries. 

What are the Findings of the Source Water Assessments in Maryland?

Ground water is the most commonly used source of water supply, and some regions of the State (Southern Maryland and the Eastern Shore) rely exclusively on ground water for their water needs.   In Maryland, ground water is obtained from both unconfined and confined aquifers.  Confined aquifers are more protected from contamination than are unconfined aquifers.  Almost all of the public water systems using ground water in Southern Maryland rely on confined aquifers, as do a large portion of those on the Eastern Shore.  In Central and Western Maryland, the aquifers are unconfined. 

Source water assessments conducted in Maryland indicate that the most common potential sources of contamination for systems in unconfined aquifers are underground storage tanks, service stations, dry cleaners, on-site septic systems and agriculture.  Volatile organic compounds and nitrates were the most common contaminants found in these water supplies, although microbiological pathogens were found in some wells located in limestone areas of Central and Western Maryland.  Some of the systems that are in deeper confined aquifers were found to be susceptible to naturally occurring contaminants like arsenic, fluoride and radium, but were not found to be susceptible to contaminants originating from local land use activity.

In Maryland, about 10% of the community water systems (around 50 systems) rely on surface water, yet these surface water systems serve about 80% of the population using public water systems.   Protecting a surface water source involves protecting the entire watershed, which can be relatively small (less than one square mile) to very large.  The Potomac River watershed is about 10,000 square miles and the Susquehanna Rivers watershed is about 27,500 square miles.  Some water supply watersheds (such as the Savage River reservoir watershed) are close to 90% forested while others (such as Baltimore City’s reservoir watershed) are predominately agricultural. 

Agricultural activities and urban development were the most prevalent sources of contaminants for surface water systems.   Contaminants from agricultural land include nutrients and microbial pathogens.  Excessive erosion (sediment) and deicing compounds were contaminants of concern from runoff in developed areas.  The discharge of treated wastewater and risks from overflowing sewage collection systems upstream of intakes were noted as significant source of contaminants in some watersheds.  Sources relying on river intakes are more susceptible to elevated levels of fecal contamination and turbidity following rain, while sources using reservoirs were more susceptible to eutrophication from phosphorus.  Major roads, rail lines and pipeline crossings presented the potential for spills above some intakes.

What Next?

Assessing the vulnerability of drinking water supplies is the first step toward protecting public drinking water system sources.  Specific recommendations to protect each drinking water supply are included in the source water assessment reports, which were provided to the water systems.  Water systems are encouraged to take an active role in protecting their source water.

Many activities that occur on the land surface have the potential to impact water quality in a drinking water source.  Protecting a water supply involves coordination and cooperation between various local and state agencies to ensure the following:

1. Onsite sewage disposal system, petroleum storage tanks, and other point sources are properly located and constructed;
2. Certain activities are not conducted in close proximity to water supply sources;
3. Pollution prevention measures are undertaken to the fullest extent possible; and
4. Appropriate emergency procedures are in place to ensure the quickest possible response to events occurring within a source water assessment area.

MDE has provided funds to several communities and water suppliers for wellhead protection activities and plans.  In addition, loans are also available for purchase of properties in wellhead and watershed protection areas.  Application packages for grants and loans are available from MDE's Water Supply Program.  MDE has worked with a number of local governments to help them implement source water protection measures, and will continue to work with them to ensure the safest possible sources for Maryland's public water systems.

For more information

For more information about Maryland’s Source Water Assessment Program, please contact MDE's Water Supply Program at (410) 537-3714. Your comments are welcome as Maryland implements this program.  Contact your local water supplier or water advisory group to become involved in the protection of your local water supply.