ISFAPPC04246

• Case Number: 00CW0101
• Stream Name: Fourmile Creek
• Watershed: Fourmile Creek
• Water Division: 2
• Water District: 12
• County: Fremont
• Instream Flow App - Doc Type: Supplemental Data

---..

4.0 Discussion

'.

4.1 Fourmile Creek

4.1.1 Water Quality
Results from these two fall s...mplings indicated no harm to the aquatic community
in Fourmile Creek attributable to water quality. :The flow from Carlton Tunnel and Cripple
Creek increased the hardness, conductivity $nd sulfate in Fourmile Creek. The high
hardness values would have mitigated metal~ toxicity, However, Fourmile Creek metal
concentrations were close to, or less than, detebtion limits, not elevated to toxic amounts.
The metal concentrations in the stream were mostly a decimal point less than toxic
concentrations,

4.1.2 Macroinvertebrates
The presence of mayflies, caddis flies, ar)d stoneflies at all Fourmile Creek locations
was indicative of a relatively clean water, hi9r-quality Rocky Mountain stream. These
three groups plus Simulium sp.(black flies) and Coleoptera (beetles) comprise almost
100% of benthic fauna in Colorado streams (Ward and Kondratieff 1992). These five taxa
dominated the Fourmile Creek macroinvertebrate community, In general, the majority of
the same taxa and species was collected at each station both sampling years.

d--:-.

~..' .

The numbers of macroinvertebrates ~lIected in Fourmile Creek were fairly
comparable between years although 467 orgClnisms were collected in 1994 at Fourmile
Creek downstream of Cripple Creek versus 1,206 in 1995, This may seem to be a large
increase from one year to the next except that the DOW sampling technique was not
designed to produce quantitative data for inferential analysis. Needham and Usinger
(1956) found that 73 Surber square-foot samples were required to reach 95% confidence
limits for total numbers of macroinvertebrates present, while two samples provided a
representative species list. The DOW kick screen methodology was designed to provide
a reasonably accurate species list with apprqximate information regarding numbers of
macroinvertebrates present. '

Several monitoring programs have not~d extreme variation in macroinvertebrate
distribution at a single sampling site. Data from ,one such monitoring program by the EPA
on the Eagle River are included as Appendix C. The EPA data are from one sampling site
used as the control location for theEPA Eagle River monitoring program. These data
demonstrate the extreme variability of macroinvertebrate results at this site every year,
In 1990, there was a 50% change in the number of macroinvertebrates per square foot at
the control site while in 1993, numbers ranged frpm 19 to 636 per square foot. The reason ,
for this variance is the patchy distribution of aquatic macroinvertebrates. Hundreds of a
given species may be found at one small location, while only a few inches away an entirely
different species is abundant. If the number of taxa collected increased between years,
as well as the number of organisms, then there may be a difference between years or
sites.

:....::..~.':

10

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I