Impact of Forest Service Activities on Stream Flow

• File Number: 8461.250
• Description: Water Issues
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 5/22/2003
• Author: Charles A. Troendle, James M. Nankervis, Laurie S. Porth
• Title: Impact of Forest Service Activities on Stream Flow
• Water Supply Pro - Doc Type: Report/Study

Troendle/Nankervis/PortYi Page20 5/22/2003
double mass plotted the snow course data from the 16 remaining stations over that for the Glade
Creek station. We kept 4 of the Coloradc? and 6 of the Wyoming snow courses. The compazison
of snow pack accumulation at Big South, in the Poudre River draina.ge did not compare well with
Glade Creek (Figure 18) while the Long:> Peak site was a good comparison (Figure 19). The 10
snow courses selected foir further analysiis are listed in Table 2 of Appendix C along with their
location and length of record.
BIG THOMPSON RNER. AT ESTES PARK C0.:06733000 &
ENCPMPMENT RN AB HOG PA,RK CR NR ENCAtv1PMEN'I' WY0:06623800
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06623800: Cumulative WYR DMF (cfs)
Figure 16. Example of a;stable double-mass comparison. The stream flow measured on the Big
Thompson River and at Hog Park aze strongly related indicating that the stream flow
measured at orie site is not changing relative to that measured at the other site.
In order to improve the analysis, we also assessed the availability of long-term precipitation data
to also compare with the stream flow data. Precipitation for Colorado and Wyoming can also be
obtained through the NRCS website " ://www.wcc.nres.usda.gov. We identified 10 sites, 8 in
Colorado and 2 in Wyoining that were currently in operation and had 50 or more years of
continuous record. We then compared those sites in a double-mass format with the snow course
data from Glade Creek in Wyoming. All compazisons appeared stable (see Appendix C) so a1110
sites were retained for funther analysis. TYie precipitation sites, locations, and period of record are
presented in Table 3, Appendix C.
In Total, we retained 19 ;stream gauge locations, 10 snow courses, and 10 precipitation gauges
for further analysis. The rE:lative proximit:y of all the sites is shown in a Figure 19.
In the final selection process, all the historical stream flow record for the 19 stream gauges
selected were double-mass plotted against the over lapping record for the 3 nearest snow courses
and the 3 nearest precipiiation gauges. 'Ten of the 19 stream gauges were dropped from the
analysis and 9 sites were retained as refe;rence sites (Table 3). It should be noted that of the 9
sites selected both the Bi€; Thompson River, at Estes Park, and St. Vrain Creek, at Lyon, do not
appear to have record ,3vailable since 1998. This may imply they have been closed or
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