9317 ‎(2)‎

• UCREFRP Catalog Number: 9317
• Author: Spahr, N. E., L. E. Apodaca, J. R. Deacon, J. B. Bails, N. C. Bauch, C. M. Smith and N. E. Driver.
• Title: Water Quality in the Upper Colorado River Basin, Colorado, 1996-98.
• USFW Year: 2000.
• USFW - Doc Type: Denver.
• Copyright Material: NO

10

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NITRITE
PLUS NITRATE

TOTAL DISSOLVED ORTHO,
PHOSPHORUS PHOSPHORUS PHOSPHATE

AMMONIA

Figure 7. Concentrations of nitrite plus nitrate and total phosphorus were
greater at sites with urban development (Gore Creek and East River) than at
the reference site (Colorado River below Baker Gulch). Sites shown in order of
increasing urban development. A log scale is used due to the large range of
concentrations.

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Baker Gulch (urban (urban Baker Gulch (urban (urban
(reference site) site) site) (reference site) site) site)

Figure 8. Algal biovolume (the amount of algae) was greater at Gore Creek,
which also has greater urban development. The percentage of mayflies,
stonetlies, and caddistlies decreased, and the percentage of midges (indicative
of more degraded water quality) increased with urban development. Sites shown
in order of increasing urban development.

0.28 - Nitrite plus nitrate East River 3,000
0.26 Instantaneous discharge
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OCT JAN APR JULY OCT JAN APR JULY OCT JAN APR JULY OCT
I WATER YEAR 1996 WATER YEAR 1997 I WATER YEAR 1998 I

Figure 9. Nutrient concentrations were greatest during the late winter low-flow
period prior to peak snowmelt runoff. This pattern was similar for total phosphorus
at East River and for nitrite plus nitrate and total phosphorus at Gore Creek.

(mayflies, stoneflies, and caddis-
flies) was greater at sites with less
urban influence (Colorado River
below Baker Gulch, fig. 8). The
percentage of midges (insects gen-
erally tolerant of pollution)
increased with increasing urban
influence (East River and Gore
Creek sites, fig. 8). Even though
the percentage of midges was
greater at Gore Creek, the inverte-
brate status of Gore Creek was less
degraded than other urban sites in
the NA WQA Program (p. 8).

Nutrient concentrations were
generally largest during winter.
Concentrations of nitrite plus
nitrate and dissolved and total
phosphorus were greatest during
the late winter low-flow period
prior to snowmelt runoff (fig. 9).
With the onset of snowmelt runoff,
nutrient concentrations were
diluted. Algal uptake of nutrients
during warm weather (July-
October) probably lower concen-
trations during the summer. With
reduced dilution and diminished
algal uptake, nutrient concentra-
tions increase again during the win-
ter low-flow period.

Ground-water studies investi-
gated the effects of urban land
use on water in selected alluvial
aquifers. Although many commu-
nities in the VCOL rely on surface
water as their primary source of
drinking water, a few mountain
towns and many thousands of
individual homes in the Southern
Rocky Mountains use ground
water as their primary water
source. Effects of urban land use
can be indicated by elevated con-
centrations of nitrate, detections of
synthetic organic compounds (pes-
ticides and VOCs), and bacteria.

Major Findings 7