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

tv TD5 SO = Cl- Ca++ Hgt+ Na+
0 Site mg/l mgh mg!1 mg/1 mg/l mg/1 Depth Number of
-.J _._.............--1______ ~ -----~----_.~_._._---_..__._- (em) Observations
C..H Upper X 513 153 13 51 26 79
s 153 50 5 41 14 23 Coal Creek Channel
Spring X 2109 1176 9 1811 76 360
, 164 161 12 79 32 111 0-10 9
18
Middle -I: 1901 1137 22 184 69 315 10-20 9
8 534 363 12 166 34 128 20- 30 9
Lower X 1388 771 29 69 48 242
s 598 397 12 51, 29 153 Coal Creek Banks
_.._-----_.--~ 0-10 21
X " mean observed value 10-20 21
s ::: standard deviation 20-30 21
Coal Creek Tributary Channels
0-10 10
10-20 10
condi t ions, little or no salt uptake was 20- 30 10
observed in tbe natural channels.

Table 4,2, Observed chemical concentrations
in Coal Creek.

-----_._._----_._----~-------------_.._---~-

-----,-------,-----------~--.--~-~

r

Sixty sediment samples were taken from
channels throughout the Coal Creek study
area, and conductivities were determined for
their 1:1 saturation extracts. The objective
was to determine if significant differences
as salinity sources existed in materials
taken from different depths, between banks
and beds, and between main stem and tributary
channels. The resulting chemical extract
data are listed in Appendix C (Table C-3).

The predominant anion extracted was
sulfate, with an observed mean cqncentration
of 2245 mg/l and a standard deviation of
1955 mg/l. Much smaller concentrations of
chloride and carbonates were found. The
predominant cations were calcium, magnesium,
and sodium with means of 299, 179, and 426
mg/l and standard deviations of 168, 217,
and 587 mg/l, respectively. Relatively small
concentrations of potassium were also found.

The means and standard deviations of
the conductivities of the channel sediments
segregated by the three-way classification
are listed in Table 4.3. A student t-test
was conducted to examine for significant
differences among means assuming unequal
variances (Lapin 1975). The results are
listed in Table 4.4.

The only significant differences de-
tected were in the bank materials and at
depths greater than 10 cm between Coal Creek
and its tributaries, and these were only
valid at the 95 percent level. Significant
salinity differences related to channel
processes or geomorphology, even if they
exist, are very difficult to detect because
of extreme heterogeneity of Mancos Shale and
Mancos Shale derived soils in the area (Ponce
1975) .

I

To estimate the approximate magnitude of
efflorescence in the natural channels, 1 em
deep soil samples were taken at the sites of

Table 4.3. Soil conductivities for beds and
banks for Coal Creek locations.

Average
(nunhos
@ 250e)

Standard
Deviation
(mmhos
@ 250e)

2.34
1. 99
2,22

2.24
3,00
3.18

3,30
2,66
2.92

2.60
2,13
2.53

10.82
8.50
5.21

12.69
13,50
4.13

Coal Creek Tributary Banks

0-10
10- 20
20-30

20
20
20

6.13
5,01
5.37

5.87
3.55
4.15

the sediment samples of February 9 and July
8, 1977. From the efflorescence samples, the
conductivity was measured, the TDS was esti-
mated (Equation 4.2), and the efflorescent
density in gm/m2-cm was calculated.

TDS

1.04 (EC) - 551

. . (4.2)

in which

TDS Total dissolve~ solids in mg/l
EC Conductivity in mmhos/cm @ 25'C

The results are listed in Appendix C. The
estimated eff1uorescent density ranged from a
low of 18 gm/m2-cm to a higb of 9387 gm/m2-cm
measured in a Coal Creek tributary called
Bitter Creek. This channel receives a
small amount of interflow from the irrigated
farmland (Figure 3.1). The mean effluorescent
density was 1187 gm/m2-cm with a standard
deviation of 2230 gm/m2-cm. The predominant
efflorescent source is believed to be soi1-
water evaporation as described by Nakayama et
a1. (1973) and resulting in particularly
heavy deposits on concave surfaces below
saturated soil profiles and other locations
where soil water comes to the surface.

Mineral dissolution from the
Coal Creek cbannel material

Salt dissolution rates were measured in
the laboratory by placing samples of un-
weathered Mancos Shale in quiescent distilled
water and measuring conductivities of the
solution periodically. For this purpose, six
shale samples each were taken from four
Coal Creek sites.

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