Resource
managers need to understand the "lag time"
between the implementation of management practices
and improvement in water quality in the Chesapeake
Bay to help develop future nutrient- and sediment-reduction
strategies. One factor affecting the lag time
is the influence of ground water on the transport
of nitrogen to streams in the Bay watershed.
Ground
water supplies a significant amount (about half)
of water and nitrogen to streams in the watershed
and is therefore an important pathway for nitrogen
to reach the Chesapeake Bay.
The
age of ground water in shallow aquifers in the
Chesapeake Bay watershed ranges from modern
(less than 1 year) to more than 50 years, with
a median age of 10 years.
In
addition to ground water, stream water will
be influenced by surface runoff and soil water.
Runoff and soil water both have very young ages
(hours to months) and supply, on average, about
half of the water to a stream.
Proposed water-quality criteria
in the Bay probably will not be met by 2010
due to the time needed to implement management
practices and the effects of ground water and
other watershed properties on nutrient transport.
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