WSP07478

• File Number: 8272.600.60
• Description: Colorado River Basin Salinity Control Program - Basin Member State Info - Utah
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 3/1/1982
• Title: Salt Uptake in Natural Channels Traversing Mancos Shales in the Price River Basin - Utah
• Water Supply Pro - Doc Type: Report/Study

seepage losses. At a particular time, the
rate of salt loading decreased in the
downstream direction. From these trends, the
~ accumulated salt load per unit area from the
e:> fixed and suspended channel bed materials may
00 be described by Equation 4.3. Multiplication
"...., by the bed area to estimate the total aalt
_.n load gives,

C ~ Kl . T . L . WP. . . . . . . . (4.5)
in which

C ~ The accumulated salt load in grama
at distance, L, from the point of
flow introduction st time, T
T ~ Time in minutes from the beginning
of flow
kl = The salt loading coefficient
(gm/mi nO. 5_ f t2)
L - channel length in feet
WP - Wetted perimeter in feet

In a concurrent study, flows were induced in
six small channels .in the Price River Valley
(White 1977b) on three separate occasions.
The channels were monitored at points 10, 25,
50, and 100 feet downstream from where the
flow was introduced. The flow was held
steady, and inflow, outflow, and wetted
perimeter were measured. By least SQuares
regression, a loading coefficient (Kl in
Equations 4.3 and 4.5) was calculated for
each induced flow. At the 100-foot position,
all of the conelation coefficients exceed
0.98.

A plot of the regression estimated rates
of dissolution per unit of wetted area for
channel 2-1 (White 1977b), located in the
Coal Creek subbasin, is illustrated in Figure
4.24. The dissolution rates after the fiut
25 feet decline approximately linearly with
channel length. The decline supports the
observations of the Coal Creek macrochannel
study. Th is trend li kely reflects a reduc-
tion in channel sediments pickup as the
sediment carrying capacity of the flow is
approached.

However, not all channels responded with
a negative slope (Figure 4.25). The dissolu-
tion rates in channel 1-2, located outside of
the Coal Creek drainage, increased after the
flow passed the 50-foot pOint, probably due
to heterogeneity in the salinity of the
channel materials. Dissolution rate changes
should be expected where flows cross onto a
different bed material.

An average rste of salt loading (Kl)
for the Coal Creek study area was estimated
by averaging the observed loading rates from
channels within the area. The result was an
average loading rate of 2.51 gms/minO.5 per
square foot of channel with a standard
deviat ion of 3.17 gm/mi nO. 5 per square- foot
of channel, indicating a great deal of
vsriation among locations.

f- 15 DATE FLOW
z --+- 6/29/76 ,0981 ols
UJ --+- 7113/76 ,0442c:f.
U
if ~ ----- 7/27/76 ,176 of.
UJN 10
o .t:
u , ).
III .....
<!lOc
Z ,-
- E . -=-
o ....
<t '" 5
o 5-
-'-
f-
-'
<t
(/) 0
0 25 50 75 100
CHANNEL LENGTH (feet)

Figure 4.25.

Channel 1-2 BaIt loading coef-
ficient.

44