WSP10787

• File Number: 8170
• Description: Arkansas Basin Water Quality Issues
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 9/1/1981
• Author: Bureau of Reclamati
• Title: Heavy Metals Pollution of the Upper Arkansas River - Colorado - and its Effects on the Distribution of the Aquatic Macrofauna
• Water Supply Pro - Doc Type: Report/Study

Station AR-6 is about 100 m downstream of a
wooden bridge on the Pan-Ark property just east
of U.S. Highway 24. Sand and 31- to 119-mm-
diameter gravel and rubble compose most of the
substrate.

Station AR-7 is located about 200 m below the
inflow of Box Creek from the west. The river
parallels the railroad track in this area and has
been channelized. Steep bluffs confine the river
to a relatively deep, narrow channel. Sampling
was done in a riffle area of the river containing
primarily 30- to 148-mm-diameter gravel and
rubble.

Station AR-8 is immediately upstream of the
confluence with Lake Creek. This river section
also appears to have been channelized and the
channel is deep and narrOW. Large boulders
were present along the river's edge. Most of the
substrate sampled consisted of 81- to 291-mm-
diameter rocks.

Station AR-9 is located 0.8 km below the Lake
Creek inflow. Varying flows from Twin Lakes via
Lake Creek result in widely fluctuating flows at
this station in the Arkansas River. Lake Creek in-
flows usually freshen the Arkansas River consid-
erably at this station. The substrate consists pri-
marily of 42- to 139-mm-diameter gravel and
rubble.

Data Collection and Sampling Techniques

Data collection and sampling were done ap-
proximately twice monthly from March through
November 1979 and four times from April
through September 1980. On each sampling
date, physical water parameters were measured
and water samples for chemical analyses were
collected. Macroinvertebrate samples to deter-
mine density and diversity were collected at all
times except during the first and last surveys of
1979, during which slush and ice in the river
would not allow accurate sampling. Fish popula-
tion estimates were done by collecting fish at
selected stations during a low-flow period in the
fall of 1979 using a battery-operated backpack
electrofishing unit. Fish liver samples for
analysis of heavy metal content were later ob-
tained from these collections. In addition, on one
occasion during the fall of 1979, physical water
quality parameters were measured and water
samples for chemical analyses were collected
from four significant tributaries to the upper
Arkansas River.

The field parameters measured during this study
were temperature, dissolved oxygen, conduc-
tivity, pH, and oxidation-reduction potential.
These parameters were measured with a Hydro-
lab Corporation Surveyor multipara meter probe
(fig. 4) IHydrolab, 1972 1821). East Fork and
California Gulch flows were measured with a
Price current meter (fig. 5) and staff gages,
using techniques developed by the Bureau of
Reclamation 11967) 117]. Major Arkansas River
flows were obtained -from U.S. Geological
Survey and State of Colorado stream gaging sta-
tions.

Polyethylene plastic bottles were used to collect
all water samples. One-liter samples of water
were collected and refrigerated for major cation-
anion analyses. A 150-mL bottle was used to
collect water for the analyses of various heavy
metals. Approximately 1 mL of nitric acid was
added to the heavy metals samples to lower the
pH to less than 2.0 to maintain the metals in
solution. Thus, analytical results reflect the total
metal concentrations. Five-hundred-mL samples
of water were collected and frozen for analyses
of phosphorus and nitrogen compounds.

The substrate was measured on one sampling
date. The smallest diameter of the smallest sur-
face stone and the largest diameter of Ihe
largest stone within the enclosed area of three
Surber samples were m~"sured. This described
the ranges of substrate sizes at each station.

The macroinvertebrate community was sampled
using a Surber sampler (fig. 61. A description of
this sampler can be found in Welch 119481
1163]. According to Cummins (1962) [31].
the Surber sampler is the most widely accepted
macroinvertebrate sampler, particularly in
waters of less than 300-mm depth with
moderate flow. The sampler consists of two
nesting 300-mm-square brass frames attached
on one side to form a 900 angle when opened.
An attached conical net made of 1 -mm mesh is
attached to the vertical frame. The sampler is
placed on the stream bottom with the open end
of the conical net facing upstream. All substrate
within the 0.09 m' area defined by the
horizontal frame is washed by hand in front of
the open net. The current carries any dislodged
organisms into the net. Even though the opera-
tion of this sampler has some disadvantages,
such as the collection of drifting organisms, the
limitation to relatively shallow water, the dif-

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