Chemical composition of stream water in mixed alpine & subalpine watersheds
at the Fraser Experimental Forest, Colorado
1USFS
Greenness
Brightness
Overview
In high-elevation watersheds, variability in streamwater chemistry,
nutrients and carbon respond to complex spatial patterns in vegetation,
soil and the physical environment. High-elevation watersheds are sensitive
indicators of changing climatic conditions and atmospheric inputs to alpine
and treeline ecosystems. Greater understanding of interactions between
terrain features and watershed processes will lead to better monitoring of
ecosystem change in complex mountainous terrain.
At the Fraser Experimental Forest in central Colorado, we analyzed
streamwater in 19 headwater tributaries of the Fraser River and locations
along the river’s main stem. We also developed terrain models and
hydrological distance surfaces to characterize upland and riverine
geomorphic variability in order to develop basin-wide characterizations of
factors that regulate biogeochemical and hydrologic processes. This
method accounts for non-linear relationships between spatially-explicit
physical features of a watershed and point estimates of parameters such as
the extent of exposed rock or steep slopes and Normalized Difference
Vegetation Index (NDVI) and generates a representation of the landscape
relationships that contribute to watershed biogeochemical fluxes.
Wetness
Soil and Crop Sciences
Colorado State University
Fort Collins, CO
Tributaries
Watershed
Area
ha
Gordon
Iron
Mine
Range
Lunch
274.5
781.6
250.6
774.8
295.9
153.7
374.6
116.4
354.5
120.3
56.0
47.9
46.5
45.7
40.7
66.4
59.2
46.6
27.7
70.1
37.2
28.4
21.6
12.7
28.5
2.8
4.1
4.2
3.2
4.0
298.54
248.11
149.14
179.95
225.15
0.94
0.86
0.86
0.75
0.81
59.35
68.54
51.83
79.02
71.85
0.05
0.12
0.12
0.23
0.17
0.73
1.16
1.27
1.44
1.17
East St Louis
Byers
Lexen
South Deadhorse
Wyssen
Main Deadhorse
West St Louis
Upper Fool
Lower Fool
North Deadhorse
Alder
Monik
Short
941.3
353.9
129.9
125.6
374.3
319.5
488.9
129.4
307.3
21.0
27.5
2.7
68.8
290.9
50.6
15.9
13.7
18.4
14.1
18.4
1.6
1.6
0.0
0.0
0.0
0.0
30.9
14.3
12.3
10.9
4.9
4.4
3.8
1.2
0.5
0.0
0.0
0.0
0.0
25.0
49.1
44.3
68.2
48.3
67.7
48.3
0.00
0.0
0.0
0.0
0.0
0.0
7.7
7.0
5.4
7.5
2.4
3.0
1.8
0.0
0.0
0.0
0.0
0.0
0.0
3.1
3.4
1.6
2.2
2.6
2.7
2.7
1.5
2.8
0.0
0.0
0.0
5.0
58.83
123.76
15.79
29.38
17.07
23.74
17.80
17.95
3.62
19.51
11.72
9.95
9.13
0.50
0.70
0.27
0.45
0.23
0.38
0.23
0.14
0.07
0.21
0.16
0.18
0.07
93.22
71.41
68.17
58.12
83.85
76.76
81.20
122.25
115.08
107.20
93.94
66.63
155.73
0.46
0.27
0.64
0.52
0.66
0.56
0.72
0.83
0.92
0.76
0.79
0.81
0.87
1.72
1.18
0.99
0.57
2.55
1.06
1.71
2.31
2.56
2.17
1.76
2.03
2.69
639.6
2089.7
3388.3
8507.2
259.6
1141
636.3
1900
40.6
30.45
33.66
22.34
33.9
40.0
38.4
40.8
13.8
12.9
12.2
9.1
3.9
4.2
4.1
4.7
139.13
146.75
155.79
65.40
0.61
0.70
0.70
0.45
111.54
92.30
89.78
98.00
0.37
0.28
0.27
0.51
2.32
2.36
1.99
2.06
Main Stem Stations
Upper St Louis
St Louis abv Range
St Louis abv Diversion
St Louis @ USGS gauge
Radiation
Alpine &
Rock
Alpine
Area
ha
%
2Dept
Alpine
Valley
Rock
Bottom
% of Alp % of Basin
%
25
NDVI
Nitrate (meq L -1 )
Chuck Rhoades1, John Norman III2, Eugene Kelly2 & Kelly Elder1
Rocky Mountain Research Station
Fort Collins, CO
crhoades@fs.fed.us
-
NO3 -N
mg/L
%
DON
mg/L
%
DOC
mg/L
A lp in e E x t e n t ( % )
20
15
10
r2 = 0.67
y = 0.29x - 0.02
5
0
0
10
20
30
40
50
60
Study Area Description
Streamwater Analysis
Streamwater was sampled monthly during 2005 and 2006.
Concentrations of major cations and anion were quantified by ion
chromatography. ANC was measured by Gran titration to a 3.2
endpoint and pH and EC were measured using glass electrodes.
Dissolved organic carbon and TDN were determined by hightemperature combustion catalytic oxidation
15
10
r2 = 0.73
y = 0.58x + 0.40
5
0
Upper Fool
East St Louis
Range
Lower Fool
7.4
7.5
7.5
7.6
35.0
38.4
45.7
54.9
2+
+
176.9
215.2
302.2
327.1
70.4
79.6
78.4
118.9
103.9
90.2
91.8
120.9
+
18.9
17.0
15.5
23.4
4
280.6
288.3
304.4
469.3
2-
33.9
46.8
69.1
45.1
3
-
1.3
4.2
12.9
0.3
Streamwater Nitrogen
Cl
4.0
4.3
4.1
5.0
514.6
521.1
591.7
600.6
615.5
650.4
655.6
678.6
692.1
792.6
119.1
239.6
226.2
147.0
263.7
134.9
163.0
273.0
196.3
258.8
59.2
48.3
75.7
75.7
93.4
52.9
55.9
114.0
80.8
56.0
31.9
22.4
39.2
18.0
35.2
37.0
28.2
50.1
32.0
24.6
555.0
624.4
796.6
725.9
837.6
577.3
623.5
917.9
889.3
791.0
95.0
114.2
58.7
39.0
68.1
209.3
220.5
94.9
59.2
248.0
8.8
10.7
1.2
1.1
0.7
17.7
16.1
0.8
1.4
21.3
4.7
3.6
8.8
5.1
6.4
4.2
4.1
8.0
6.3
3.6
Sedimentary Bedrock
Monik
Main Deadhorse
South Deadhorse
North Deadhorse
8.0
8.1
8.1
8.1
145.4
134.7
137.1
167.1
1023.0
1076.6
1121.0
1370.9
263.8
220.5
227.1
294.5
135.9
83.6
67.0
104.3
53.1
33.7
25.2
28.6
1305.5
1264.3
1310.9
1614.5
101.1
56.9
38.8
66.7
0.7
1.7
2.1
1.4
9.7
5.5
4.0
5.9
Main Stem Stations
Upper St Louis
St Louis abv Range
St Louis abv Diversion
St Louis @ USGS gauge
7.5
7.7
7.6
7.9
49.8
70.8
67.0
90.6
340.0
472.9
463.5
615.6
91.1
163.6
145.3
194.3
78.2
76.7
76.3
104.8
12.8
18.7
19.2
28.6
346.2
518.3
473.5
732.9
94.3
126.3
120.2
106.7
9.9
10.5
11.1
4.7
5.6
4.3
4.2
6.0
89.9
(44.2)
659.0
(398.3)
780.6
(455.1)
75.8
(56.1)
4.7
(6.0)
r2 = 0.59
y = -91.6x + 47.8
0 .4 0
0 .4 5
0 .5 0
0 .5 5
0 .6 0
•In general, DOC concentrations were highest in basins with no or low alpine cover.
•The basin with the highest DOC (Short Ck) had the greatest extent of valley
bottom (5%), though this terrain attribute was a poor predictor of DOC.
1200
1400
1000
Sedimentary
1000
800
600
Mixed
400
200
Metamorphic
0
0
200
400
600
800
1000 1200 1400 1600
ANC (μeq L -1 )
25.2
(10.0)
5
0
DOC
-
71.2
80.2
90.9
79.7
96.6
88.2
94.5
106.0
99.7
113.1
86.8
(24.4)
15
10
0 .3 5
7.8
7.8
7.9
7.8
7.9
7.8
7.8
7.9
7.9
7.9
171.3
(79.0)
40
-5
1200
7.8
(0.3)
30
•Nitrate concentrations in the 5 basins with
> 40% alpine cover are 10X higher than the other 13 basins.
•Nitrate comprised 75 to 94% of the total dissolved nitrogen in the five high
nitrate streams, but it was less than half of TDN in the others.
•Exposed rock represents 13 to 37% of the basin area of the five high
nitrate streams compared to less than half that in the remaining basins.
•DON concentrations are 30% lower on average for the high nitrate streams.
Mixed Parent Material
Byers
Mine
Wyssen
Lexen
Short
Iron
Lunch
Alder
West St Louis
Gordon
Overall Mean
SD
20
B a sin N D V I
4.9
(2.7)
Streamwater Chemistry
1200
Exposed Rock
in Alpine (%)
Alpine
Greenness
1000
800
Calcium (μeq L -1)
Brightness, greenness, and wetness analyses are a product of the
Tassel Cap Transformation based on PCA-like techniques. This
procedure reduces the spectral dimensionality of the 7 Landsat
TM bands into 3 bands that explain ~98% of the spectral
variability.
Brightness: Soil moisture dynamics (75% of variability)
Greenness: Vegetation vigor without soil reflectance influences
(15% of variability).
Wetness: Soil/ canopy moisture relationships (8% of variability).
Radiation: A unitless index of potential solar influence (0= high
radiation to 1= high shade) from a raster algorithm and 10m
DEM.
NDVI: Normalized Difference Vegetation Index analysis is a ratio
of red and near IR bands to assess chlorophyll and soil reflectance
Ca
Mg
Na
K
pH
EC
ANC
SO
NO
andBedrock
index above ground biomass.
Metamorphic
2+
10
25
-1
The proportion of each study basin located above treeline ranges from 0
to 56%. The smallest basins did not extent above treeline, but there
was no consistent relation between basin size and alpine cover. For
example, several smaller basins situated near the upper portion of the St
Louis Creek basin (e.g. Lunch, Gordon, and Mine Cks) had among the
highest alpine cover. Exposed rock covers as much as 70% and averages
44% of the alpine area. Valley bottom covers about 2.5% of the basins
on average.
20
A lp in e R o c k E x t e n t ( % )
0
Terrain Analysis
Calcium (μeq L )
N
The 19 tributaries of St Louis
Creek cover <10 to nearly
1000 ha with an average area
of 315 ha. Individual tributaries
span as much as 1000 m in
elevation with an average of
624 m of relief.
Treeline
averages 3482 m elevation and
ranges from 3242 to 3654 m.
The individual tributaries are
nested within the 8500 ha basin
gauged by USGS St Louis Creek
Station 09026500 located at
39°54'36" N, 105°52'40" W and
2735 m elevation (USGS
2008).
Calcium (μeq L -1 )
Fraser Expt Forest
-1
Nitrate (meq L )
St Louis Creek Basin
-1
Nitrate (meq L )
25
20
600
400
r2 = 0.71
y = 11.4x + 128
200
800
600
400
r2 = 0.84
y = -40.6x + 1956
200
0
0
0
20
40
60
80
20
25
30
35
40
•The pH of St Louis Creek tributaries averages 7.8 and ranges from 7.4 to 8.1
•Streamwater calcium and ANC are regulated by basin bedrock with differences
between basins containing sandstone and shale, those formed on
metamorphic material and basins with mixed geology.
•The extent of exposed rock and the spectral greenness of the Alpine explain 71
and 84% of the variability of streamwater calcium, respectively and
related similarly to ANC.
45