Conceptualization and analysis
of ground-water flow in the Coastal Plain aquifers of Virginia and
parts of Maryland and North Carolina
Professional Paper 1404-F
By J.F. Harsh and R.J. Laczniak
Abstract
The ground-water flow system in the Coastal Plain of Virginia and
adjacent parts of Maryland and North Carolina consists of a
water table aquifer and an underlying sequence of confined
aquifers and intervening confining units composed of
unconsolidated sand and clay. A digital flow model was developed
to enhance knowledge of the behavior of the ground-water flow
system in response to its development. Ten pumping periods
covering 90 yr of withdrawal simulated the history of
ground-water development. Simulated potentiometric-surface maps
for 1980 show lowered water levels and the development of
coalescing cones of depression around the cities of Franklin,
Suffolk, and Williamsburg and the town of West Point, all in
Virginia. The largest simulated decline in water level, about
210 ft was near Franklin. Water budgets indicate that over the
period of simulation (1891-1980): (1) pumpage from the model
area increased by about 105 Mgal/d; (2) lateral boundary outflow
increased by about 5 Mgal/d; (3) ground-water flow to streams and
coastal water decreased by about 107.5 Mgal/d; (4) lateral
boundary inflow increased by about 0.7 Mgal/d, and (5) water
released from aquifer storage increased by about 1.6 Mgal/d.
Simulated rates of recharge into the confined aquifer system at
the end of the final pumping period (1980) varied up to 3.8 in/yr. and
simulated rates of discharge out of the confined
system varied up to 2.2 in/yr. Results of simulations show an
increase of about 110 Mgal/d into the confined system from the
unconfined system over the period of simulation. This increase
in flow into the confined system affected local discharge of
ground water to streams and regional discharge to coastal water.
Lowering the storage coefficient of the aquifer had a minimal
effect simulated water levels, whereas increasing the storage
coefficient had a much more significant effect.
Citation:
Harsh, J.F., and Laczniak, R.J., 1990, Conceptualization and analysis of ground-water flow system in the Coastal Plain of Virginia and adjacent parts of Maryland and North Carolina, in Regional Aquifer-System Analysis-Northern Atlantic Coastal Plain: U.S. Geological Survey Professional Paper 1404-F, 100 p.
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