WSP03634

• File Number: 8102.400
• Description: Arkansas River Hydrology - Transmountain Diversions-Imports
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 2/10/1998
• Author: USGS
• Title: Methods to Determine Transit Losses for Return Flows of Transmountain Water in Fountain Creek Between Colorado Springs and the Arkansas River-Colorado
• Water Supply Pro - Doc Type: Report/Study

00025B

Bank Storage

In a typical stream-aquifer system, water flows from the alluvium to the
stream under baseflow conditions. The introduction of a water wave
in the stream increases the head (water level) in the stream to a level
greater than the head in the alluvium, resulting in either a decrease in the
rate of flow from the alluvium to the stream Or in the flow of water from the
stream to the alluvium. The flow of water from the stream to the alluvium
results in bank storage. For this study, the water wave results from
introduction of transmountain return flows into Fountain Creek; the flow
antecedent to the water wave is native streamflow, including return flows of
native water used by the city of Colorado Springs.

As head in the stream decreases, bank-storage water returns to the stream
when the head in the aquifer is greater than the head in the stream. However,
the rate at which bank-storage water returns to the stream is less than the
rate at which the water flowed into the alluvium. After passage of a water
wave, the rate of return initially may be large but decreases steadily with
time. Therefore, a long period of time (termed recovery period in this
report) is necessary for the bank-storage water resulting from a given water
wave to return to the stream. In theory, if the recovery period is
sufficiently long, virtually all bank-storage loss could return to the stream;
thus, bank-storage loss only would be a temporary loss. In practice, though,
it is impracticable to consider these extremely long recovery periods because
the quantities of water in consideration after long time periods are too small
to accurately measure. Thus, some quantity of transmountain return flow
generally will be permanently lost to bank storage. Transit loss resulting
from bank storage, therefore, is highly dependent on the duration of the
recovery period during which the bank-storage water returns to the stream.
Effect of recovery period in reference to the present study will be discussed
more fully and illustrated in the "Selection of Recovery Period" section of this
report.

Any given quantity of transmountain return flow in bank storage also is
subject to four additional potential sources of loss: (1) Specific
retention; (2) evaporation through soil surfaces; (3) transpiration by
plants; and (4) withdrawal by wells. Specific retention will be discussed
here; the other three potential losses will be discussed in subsequent
paragraphs.

Specific retention of a rock or soil is defined as the ratio of (1) the
volume of water which a rock or soil, after being saturated, will retain
against the pull of gravity to (2) the volume of the rock or soil (Lohman and
others, 1972, p. 12; also see Heath, 1983, p. 8). .Loss of bank-storage water
to specific retention is a loss which only needs to be considered once.
Since transmountain return flows have been introduced into the Fountain Creek
system prior to this study, the specific retention loss has been realized
and need not be considered further. Increases in the rate of transmountain
return flow could result in additional losses to specific retention; these
additional losses also would be one time. However, the additional specific
retention losses would be small compared to other long-term transit losses
and will not be considered in this study.

12

~t;,

)'::"".

"
"'1:-"

; ~.

,.

:',:\

".
. .'

>. ~

~:~~;.
,.

~'.':.w'

,:,.

'.t"

"'""

',"
t.;

.,C'

~,-, -1

>:~ :
.......
, .

"~'