Cost-effective strategies for source-water protection
and management
Not
all water resources are equally vulnerable to contamination. Even
areas having similar land uses and sources of contamination can
have different degrees of vulnerability and, therefore, different
response rates to protection and management strategies. NAWQA findings
clearly demonstrate that natural features—such as geology, soils,
and hydrology—and land-management practices—such as tile drainage
and irrigation—can affect the movement of chemicals over land or
to aquifers. Effective management of nonpoint source pollution may,
therefore, require targeted strategies based on different degrees
of vulnerability rather than uniform treatment of contaminant sources.
Linking knowledge on natural features with the use, occurrence,
and transport of chemicals through the watershed makes it easier
to set priorities in streams and aquifers most vulnerable to contamination
and increase the cost-effectiveness of strategies designed to protect
water resources in diverse settings.
State of Washington—The Washington State Department of Health,
in concert with USGS, assessed the vulnerability of public water-supply
wells to pesticide contamination based on geology, well characteristics,
land-use activities, and low levels of detection. NAWQA information
on pesticide contamination enabled the health department to identify
wells with low vulnerability to contamination and obtain waivers
for quarterly monitoring required under the Federal Amendments to
the Safe Drinking Water Act, 1996. By using the information to meet
USEPA requirements for safe drinking water, Washington State was
able to protect their drinking-water source while saving at least
$6 million in costly additional monitoring. This is an annual savings
of as much as $70 per household on small public supply systems that
were granted full monitoring waivers.
State of New Jersey—NAWQA data on organic compounds are
used heavily in New Jersey’s source-water assessment. USGS and the
New Jersey Department of Environmental Protection are developing
models to assess the vulnerability of public water supplies (including
surface-water intakes and ground-water community and non-community
wells) in the State to contamination by regulated compounds.
I coordinate the Upper Mississippi River Source Water Protection
Initiative, an effort that will lead to the development of source-water
protection plans for public water suppliers within the upper Mississippi
River basin. The water quality data that have been generated and
documented through NAWQA will figure prominently in the preparation
of these plans. The information on certain contaminant levels in
various settings within the basin, and the information describing
the sources of contaminants provide documentation and solid rationale
for identifying source water protection strategies, priorities,
and protection measures for public water suppliers. In my opinion,
more than any single information source, the Upper Mississippi River
NAWQA provides an extremely valuable substantive basis for source
water protection in the Upper Mississippi River basin (Mr. David
Brostrom, Coordinator, Upper Mississippi River Source Water Protection
Initiative, March 2001).
In addition to the examples cited above, more than
30 other states use USGS information to develop source-water protection
plans for drinking-water sources. The collaborative projects in
these states address nearly 40 percent of the nation’s public water
supply, serving more than 90 million people.
USGS information is also used widely by states to
develop management plans for constituents, such as pesticides, nutrients,
and MTBE. Specifically, state environmental and natural resource
agencies prioritize streams and ground-water areas for assessment
of these constituents on the basis of vulnerability concepts, contaminant
occurrence data, and quality-assurance protocols of the NAWQA Program.
State of Kansas—NAWQA findings on elevated concentrations
of atrazine (frequently approaching or exceeding the USEPA drinking-water
standard) in water-supply reservoirs in the Lower Kansas River Basin
were used by the Kansas State Board of Agriculture as the basis
for establishing a pesticide management area in northern Kansas
(Delaware River Basin). Within this management area, the State of
Kansas called for both voluntary and mandatory restrictions on pesticide
usage on cropland to improve water quality. The management area
was the first in the nation to focus on reducing atrazine in runoff
to streams and reservoirs.
State of Washington—The Washington State Department of Ecology
created a Ground Water Management Area to protect ground water from
nitrate contamination. The management area covers Grant, Franklin,
and Adams counties, located in an intensive agricultural region
of the Central Columbia Plateau. NAWQA information and communication
of those findings in the USGS publication "Nitrate Concentrations
in Ground Water of the Central Columbia Plateau" provided the scientific
basis for implementing the management area. As follow-up to the
NAWQA findings, USGS works with the Department of Ecology to (1)
identify areas with lower nitrate concentrations, which could potentially
serve as sources of future drinking-water supplies, (2) statistically
correlate nitrate concentrations with natural features and human
activities to better assess vulnerability; and, (3) design a long-term
monitoring strategy for assessment of changes in nitrate concentrations
over time.
State of California—USGS works with the California State
Water Resources Control Board and Department of Health Services
to assess the vulnerability of public supply wells to contamination.
The State uses USGS ground-water-age-dating analyses as one indicator
of vulnerability. In addition, on the basis of NAWQA findings on
the occurrence of industry-related and petroleum-based chemicals
in ground water, the State has included the collection and analysis
of VOCs in their vulnerability assessment. More than 200 wells have
been sampled in southern California, and these efforts will be extended
to northern California and the Central Valley.
State of Idaho—NAWQA information formed the framework for
predictive models and maps showing the vulnerability of ground water
to contamination by the widely used herbicide atrazine in Idaho.
The maps are used by the Idaho State Department of Agriculture to
develop its State Pesticide Management Plan. Atrazine data from
the NAWQA study in the Upper Snake River Basin were used to calibrate
and verify the predictive models, which showed that significant
factors associated with elevated atrazine concentrations in ground
water were atrazine use, land use, precipitation, soil type, and
depth to ground water. These modeling tools aid in the design of
cost-effective programs for monitoring and protecting ground-water
resources throughout the State.
State of Pennsylvania—The Pennsylvania Department of Environmental
Protection works with USGS as a follow-up to NAWQA findings on the
prevalence of MTBE in ground water and its potential to contaminate
public drinking-water supplies. Through the partnership, consistent
and quality-assured data will be compiled, and a qualitative vulnerability
rating for MTBE will be developed for different hydrogeologic settings
throughout the State of Pennsylvania. The State will use the results
to prioritize areas where MTBE should be assessed and where public-supply
wells should be tested, and to target inspections of gasoline storage
tanks.
National scale—At the request of the USEPA's Office of Ground
Water and Drinking Water, the NAWQA Program published a national
map that shows the patterns of risk for nitrate contamination of
shallow ground water (available in “Nitrate
in Ground Waters of the United States—Assessing the Risk, USGS
FS-092- 96). By targeting regions with the highest risk of nitrate
contamination, resources can be directed to areas most likely to
benefit from pollution-prevention programs and long-term monitoring.
Use of risk guidelines to locate areas for prevention of contamination
also can result in cost-effective management. Once ground water
is contaminated, it is expensive and, in many cases, virtually impossible
to clean up.
Vulnerability can change over time
NAWQA findings show that the vulnerability to contamination
of streams and ground water can differ seasonally in nearly every
basin. For example, in streams that drain agricultural areas in
many parts of the nation, the highest levels of nutrients and pesticides
occur during spring and summer when recently applied chemicals are
washed away by spring rains, snowmelt, and irrigation. Excessive
amounts of contaminants can also enter streams during storm events.
For example, sampling of nutrients and pesticides through a large
storm event on the Potomac River in 1996 showed that concentrations
and total amounts of nutrients and atrazine can increase during
localized large storms, sometimes with overwhelming effects on receiving
waters, such as the Chesapeake Bay. In this case, concentrations
of individual compounds exceeded USEPA drinking-water standards
during and following the extreme storm events. Such information
helps water suppliers better understand the role of the short-term
and seasonal events, and raises considerations related to timing
of withdrawals, mixing, and storage to most effectively deliver
high quality water at a minimum cost.
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