WSP08741

• File Number: 8170
• Description: Arkansas Basin Water Quality Issues
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 1/1/1993
• Author: USGS
• Title: Reconnaissance of Water Quality of Lake Henry and Lake Meredith Reservior - Crowley County - Southeastern Colorado - April-October 1987
• Water Supply Pro - Doc Type: Report/Study

0053
Table 10. Light-transparency measurements lor all sites at
Lake Meredith
Samplng site Sampling date, Secchl-
disk depth'
<Ilg.3) 1987 (leel)
"
M2Bl 05-01 1.5
06-30 .5
. 08-20 .5
10-06 .5
MIB 05-01 1.5
06-30 .5
08-20 1.0
M4B 05-01 1.0
I 06-30 .5
08-21 .5
MIA 06-30 .5
08.20 1.0
MIC 06-30 .5
08-20 1.0
M2A 06-30 .5
08-20 1.0
M2C 06-30 .5
08-20 1.0
M3A 06-30 .5
08-21 1.0
M3B 06-30 .5
08-21 1.0
M4A 06-30 .5
08-21 .5
ILight transparency represents lhe depth to the nearest
0.5 fool at which the Secchi disk was not visible.
2M2B was the only site measured on October 6. 1987.

Chemical Constituents

I
i)

l

During the sampling period, concentrations of
total nitrogen al sile M2B ranged from less than
1.3 mgIL to less than 2.0 mgIL and averaged less than
about 1.6 mgIL (table 19). The principal nitrogen form
was organic nitrogen, which averaged about 90 percent
of the total nitrogen. The concentrations of total-
inorganic nitrogen were less than 0.2 mgIL throughout
the sampling period.
The Colorado Department of Health (1987) has
established water-quality standards for aquatic life of
0.5 mgfL of total nitrite and 0.06 mgIL of un-ionized
ammonia for Lake Meredith. Concentrations of total
nitrite at sites M2B, M I B, and M4B ranged from 0.001
to 0.022 mgfL (tables 19-21). Un-ionized ammonia is
calculated as a percentage of total ammonia, given

water temperature and pH (Willingham, 1976), and
concentrations ranged from 0.003 to 0.031 mgfL at
sites M2B, M1B, and M4B.

Concentrations of total phosphorus at sites M2B.
M 1 B, and M4B ranged from 0.062 to 0.148 mgfL and
averaged 0.106 mg!I... Orthophosphate as phosphorus
(the biologically available form of phosphorus) aver-
aged about 14 percent of the total phosphorus.

During the sampling period, concentrations of
dissolved-inorganic nitrogen at site M2B were greater
than 0.02 mg!I.. indicating nitrogen was not a limiting
nutrient (Ryding, 1988). Concentrations of dissolved
orthophosphate as phosphorus at site M2B were less
than 0.010 mg!I.. on May I, June 30, and August 20
indicating potential phosphorus limitation (Ryding.
1988). On October 6, the average dissolved orthophos-
phate as phosphorus concentration was 0.022 mgfL
indicating phosphorus was not a limiting nutrient.

The mass ratio of dissolved-inorganic nitrogen to
dissolved orthophosphate as phosphorus was greater
than 7; I on the May, June, and August sampling dates
(table II) indicating potential phosphorus limitation
(Ryding, 1988). On the October sampling date, the
mass ratio of dissolved-inorganic nitrogen to dissolved
orthophosphate as phosphorus was less than 7; I indi-
cating potential nitrogen limitation (Ryding. 1988).

Dissolved-solids concentrations at site M2B
ranged from 1,870 to 2,370 mgIL and were smallest on
June 30 and largest on October 6 (table 19). As indi-
cated by samples collected at site M2B near the lake
surface and near the lake bottom and from specific-
conduclance measurements made at the other sites in
Lake Meredith, no substantial vertical or areal varia-
tions in dissolved solids occurred on the sampling
dates. Dissolved-solids concentrations (in mgIL) in
Lake Meredith can be approximated from specific-
conductance measurements, as indicated from eight
samples collected at site M2B during the sampling
period, by multiplying the specific-conductance mea-
surement by 0.76.

Based on analysis of eight water samples col-
lected at site M2B, the predominant cation in Lake
Meredith is sodium and the predominant anion is sul-
fate. Sodium averaged about 47 percent of the cations.
and sulfate averaged about 83 percent of the anions (as
milliequivalents per liter).

The Colorado Department of Health has not
eSlablished water-quality standards for the major
chemical constituents for water use from Lake
Meredith. However. dissolved-solids concentrations
and the percentage of individual cations and anions are
important factors in water used for agricultural pur-
poses as discussed for Lake Henry.

WATER-QUALlTY CHARACTERISTtCS OF LAKE MEREDITH AND COMPARtSON TO WATER.QUALITY STANDARDS 25