9431

• UCREFRP Catalog Number: 9431
• Author: Chafin, D. T.
• Title: Evaluation of Trends in pH in the Yampa River, Northwestern Colorado, 1950-2000.
• USFW Year: 2002.
• USFW - Doc Type: Denver.
• Copyright Material: NO

8.75
Z 8.70
Z
= Q 8.65
ap
Z
Q 8.60
F
8.55
8.5
Z
W
(0 ~ ~ 8.0
X~Q~
Oa[CW
W z ~ J 7.5
~WJO=
OJV~d 7.0
~~Z
~ CJ 6.5
24
Z~
-~
+ + + + + +
+ + + + + + + + + +
+ + +
+ + + +
+
+ +
+ + ` + + +
+ + 93 percent +
118 percent of saturation +
_ of saturation + -
+
+ +
+ + + + + + + + +
+ +
+ + + + + + +
+ +
+ + +
+ +
+ + + + + -
+ + +
i
w cn 23
~ J
~ W
Q ~ 22
~~ 21
W W
F~
1200 1600 2000 2400 0400 0800 1200
25 26
AUGUST 1999
Figure 11. Diurnal measurements at Yampa River at mouth, August 25-26, 1999.
Reconnaissance Measurements in Dinosaur
National Monument
Reconnaissance field measurements taken on
the Yampa River between Deerlodge Park (site 11,
46 miles upstream from the mouth) and at mouth
(Echo Park) (site 12) during August 30 through
September 3, 1999, show pH in the narrow range of
8.43-8.77 (fig. 12), with a measurement mean of 8.63
(or 8.62 as the mean of H+ activities). Measurements
for the first 3 days indicate definite increases in pH
values (0.21, 015, and 0.33 unit) as each day
progressed, indicating possible effects of photosyn-
thesis. The smallest diurnal change (0.15 unit on
August 31) occurred on a day that was cloudy. The sky
gradually progressed from sunny to cloudy on the
afternoon of August 30, with a moderately hard,
30-minute rain at 2000 hours, and became sunny
shortly before noon after clouds and light rain on the
morning of September 1.On the fourth day, September
2, the sky was sunny for the first measurement at 0805
hours but cloudy thereafter, with a hard, 13-minute
rain beginning at 1152 hours, causing brief runoff
from the canyon walls; values of pH varied irregularly
on this day from 8.65 to 8.77.
These pH data indicate minor or no effects of
photosynthesis of the Yampa River in Dinosaur
National Monument between Deerlodge Park (site 11)
and Echo Park at the mouth (site 12). Aquatic vegeta-
tionwas sparse and scattered in the rocky streambed of
Yampa Canyon. The water had a greenish tint during
the measurement period, possibly indicating entrained,
microscopic plant cells (phytoplankton).
Although the first 3 days of measurement appear
to indicate diurnal increases in pH values (fig. 12),
these increases probably were mostly the result of
downstream depletion of reactive organic matter and
gradual venting of oversaturated, dissolved CO2.
Specific conductance (fig. 12) indicates that one rela-
tively consistent parcel of water was measured during
August 30-31, for which pH values increased regu-
larly (allowing for a small diurnal effect) from 8.43 to
8.74 as it flowed 15.4 miles downstream. There were
no flowing tributaries or springs along this 15.4-mile
reach of the river downstream from Deerlodge Park.
16 Evaluation of Trends in pH in the Yampa River, Northwestern Colorado, 1950-2000