PUB00070

• Year: 1998
• Title: Ground Water and Surface Water A Single Resource U.S. Geological Survey Circular 1139
• CWCB Section: Interstate & Federal
• Author: T.C. Winter, J.W. Harvey, O.L. Franke, W.M. Alley
• Description: Overview of current understandimg of interaction of ground water and surface water in terms of quality and quantity
• Publications - Doc Type: Historical

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The Effect of Ground-Water Withdrawals
on Surface Water

Withdrawing water from shallow aquifers that are
directly connected to surface.water bodies can have a signifi-
cant effect on the movement of water between these two
water bodies, The effects of pumping a single well or a small
group of wells on the hydrologic regime are local in scale,
However, the effects of many wells withdrawing water
from an aquifer over large areas may be regional in scale.
Withdrawing water from shallow aquifers for public
and domestic water supply, irrigation, and industrial uses
is widespread, Withdrawing water from shallow aquifers near
surface-water bodies can diminish the available surface-water
supply by capturing some of the ground-water flow that other-
wise would have discharged to surface water or by inducing
flow from surface watel into the surrounding aquifer system,
An analysis of the sources of water to a pumping well in a
shallow aquifer that discharges to a stream is provided here
to gain insight into how a pumping well can change the quan-
tity and direction of flow between the shallow aquifer and the
stream, Furthermore, changes in the direction of flow between
the two water bodies can affect transport of contaminants
associated with the moving water. Although a stream is used
in the example, the results apply to ail surface-water bodies,
including lakes and wetlands,
A ground-water system under predevelopment
conditions is in a state of dynamic equilibrium-for example,
recharge at the water table is equal to ground-water discharge
to a stream (Figure C-tA), Assume a well is installed and is
pumped continually at a rate, 0" After a new state of dynamic
equilibrium is achieved, inflow to the ground-water system

from recharge will equal outflow to the stream plus the with-
drawal from the well. In this new equilibrium, some of the
ground water that would have discharged to the stream is
intercepted by the well, and a ground-water divide, which
is a line separating directions of flow, is established locally
between the well and the stream (Figure C-1 8), If the well is
pumped at a higher rate, O2, at a later time a new equilibrium
is reached, Under this condition, the ground-water divide
between the well and the stream is no longer present and
withdrawals from the well induce movement of water from
the stream into the aquifer (Figure C-1 C), Thus, pumpage
reverses the hydrologic condition of the stream in this reach
from a ground-water discharge feature to a ground-water
recharge feature.
In the hydrologic system depicted in Figures C-1A
and C-1 e, the quality of the stream water generally will
have little effect on the quality of the shallow ground water,
However, in the case of the well pumping at the higher rate,
O2 (Figure C-1C), the quality of the stream water, which
locally lecharges the shallow aquifer, can affect the quality of
ground water between the well and the stream as well as the
quality of the ground water withdrawn from the well.
This hypothetical withdrawal of water from a shallow
aquifel that discharges to a nearby surface-water body is a
simplified but compelling illustration of the concept that ground
water and surtace water are one resource. In the long term,
the quantity of ground water withdrawn is approximately equal
to the reduction in streamflow that is potentially available to
downstream users.

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