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

Where streamflow is generated in head-
waters areas, the changes in streamflow between
gaining and losing conditions may be particularly
variable (Figure 13), The headwaters segment
of streams can be completely dry except during
storm events or during certain seasons of the year
when snowmelt or precipitation is sufficient to
maintain continuous flow for days or weeks,
During these times, the stream will lose water to
the unsaturated zone beneath its bed, However,
as the water table rises through recharge in the
headwaters area, the losing reach may become a
gaining reach as the water table rises above the
level of the stream, Under these conditions, the
point where ground water first contributes to the
stream gradually moves upstream.
Some gaining streams have reaches that
lose water to the aquifer under normal conditions
of streamflow, The direction of seepage through
the bed of these streams commonly is related
to abrupt changes in the slope of the streambed
(Figure 14A) or to meanders in the stream channel
(Figure 148), For example, a losing stream reach

Figure 13. The location where peren-
nial streamflow begins in a channel
can vary depending on the distribu-
tion of recharge in headwaters areas,
Fol/owing dry periods (A), the
start of streamflow wil/move up-
channel during wet periods as the
ground-water system becomes more
saturated (8),

A

Unsaturated
zone

Streambed
--------__~~t~!!~~~e__

B

Unsaturated
zone

usually is located at the downstream end of
pools in pool and riffle streams (Figure 14A),
or upstream from channel bends in meandering
streams (Figure 148), The subsurface zone
where stream water flows through short seg-
ments of its adjacent bed and banks is referred to
as the hyporheic zone. The size and geometry of
hyporheic zones surrounding streams vary greatly
in time and space, Because of mixing between
ground water and surface water in the hyporheic
zone, the chemical and biological character of the
hyporheic zone may differ markedly from adja-
cent surface water and ground water,
Ground-water systems that discharge to
streams can underlie extensive areas of the land
surface (Figure 15), As a result, environmental
conditions at the interface between ground water
and surface water reflect changes in the broader
landscape, For example, the types and numbers
of organisms in a given reach of streambed result,
in part, from interactions between water in the
hyporheic zone and ground water from distant
sources.

Location of
start of flow
of stream

Flowing (gaining) stream

Saturated zone

Stream su....
"aCe
Streambed

Flowing (gaining) stream

Saturated zone

Stream su....
. lace

,~':

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