9623

• UCREFRP Catalog Number: 9623
• Author: Bails, J. B.
• Title: Streamwater Quality at Selected Sites in the Fraser Basin, Grand County, Colorado, Water Years 1991-2000.
• USFW Year: 2003.
• USFW - Doc Type: \
• Copyright Material: NO

8 Streamwater Quality at Selected Sites in the Fraser River Basin, Grand County, Colorado, Water Years 1991-2000
all cases, the two trend slopes were almost identical, indicating
little sensitivity to the trend analysis because of the censored
data.
Trend analyses for ammonia at sites 1 and 2 were not
done because of the large number (greater than 20 percent)
of censored concentrations. Only site 3 had a statistically
significant trend for ammonia and showed a downward trend
in concentration for 1991-2000.
Nitrite plus nitrate trend analysis revealed two sites
(sites 1 and 4) with upward trends, although not over the same
time period, and one site (site 2) with al downward trend. The
upward trends at site 1 on both the raw and flow-adjusted data
are likely due to an increase in nitrite plus nitrate sources in
the upper reaches of the Fraser River. Because the period of
record for site 1 is different from the other three sites, a direct
relation in the trend for site 1 cannot be made with the other
three sites. The trend analysis at site 2 resulted in a downward
trend on the raw data and no trend on the flow-adjusted data.
Site 2 results indicate that the inputs of nitrite plus nitrate to
0.050
the Fraser River above site 2 are not changing, but some other
factor, such as streamflow, chemistry, or biological uptake,
is causing the concentrations to decrease. The trend results
from site 4 show the opposite conditions. Although there is
an upward trend for the flow-adjusted data, indicating a pos-
sible increase in the input of nitrite plus nitrate to the stream,
the raw concentrations remain stable. Trend analysis on
streamflow measurements at site 4 indicate an upward trend,
and this relation may be caused by site 4 being located down-
stream from the three wastewater-treatment plants.
Trend analysis was not done for orthophosphorus
at sites 1 and 2 because of the large number (greater that
20 percent) of censored concentrations. Results for the trend
analyses at sites 3 and 4 indicate upward trends in the ortho-
phosphorus concentrations at both sites. The lack of a trend
for the flow-adjusted orthophosphorus concentrations at site 4
indicates that the upward trends may be caused by streamflow
conditions and not increases in orthophosphorus inputs to the
river.
Ammonia
/\ - - Nitrite plus nitrate
\ Dissolved phosphorus
- \ Orthophosphorus
Total phosphorus
- - - Discharge
\
...........
77,
Q 0.045
°
W 0.040
IL
Z 0.035
0
l-- 0.030
z
0.025
Q
OJ 0.020
H
WZ 0.015
CE 0.010
Z 0.005
0
1.6
Q
° 1.4
w
0-
u) 1.2
z
O
F' 1.0
Z
° 0.8
O
J
w 0.6
0
0:
O 0.4
J
2
U 0.2
0
Chloride
- - - Discharge

/
/

/
/

/
/

\
\
\
\
\
\
\
\
\
\
JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV
MONTH
300
250 H
W
W
LL
200 U
E-5 Z
Z)
UO
150 U
Z W
co
W
111
100 CC
Q
2
U
50 _Ln
0
300
H
250 W
LL
U
200 m Z
UO
Zw
150 - u)
wa:
Cr CL
100 Q
2
U
U)
50 0
J0
DEC
Figure 4. Median instantaneous load for each month of selected constituents and monthly median
discharge in the Fraser River at Tabernash, site 4, 1991-2000.