WWRC 86-13
Nutrient Loading and Flaming Gorge Reservoir
Abstract
Data and analyses are presented for approximately 400 water
samples collected at eight locations in the drainage basin of Flaming
Gorge Reservoir. Up to 24 chemical parameters were analyzed from each
sample (cations: calcium, magnesium, sodium, potassium; anions:
bicarbonate, carbonate, sulfate, chloride, fluoride, total alkalinity;
nutrients: ortho-phosphorus, total phosphorus, sodium hydroxide
extractable phosphorus, ammonium, nitrate, total kjelkahl nitrogen,
iron, manganese; miscellaneous: conductivity, total dissolved solids,
suspended solids, pH, chemical oxygen demand, biochemical oxygen
demand).
In SW Wyoming, NaOH-extractable phosphorus (NaOH-P) is correlated
with biologically available phosphorus (bioassays). Data on NaOH-P,
ortho-P and suspended solids (N=541) were obtained from a sewage
treatment plant and seven streams. Scatter plots, cluster analyses
and regression analysis indicated the eight locations could be
aggregated into four GROUPs. Regressions were developed to predict
ln(NaOH-P) (LNaOH-P) from ln(suspended solids) (LSS), ln(ortho-P)
(LOP), GROUP, presence/absence of high flow, and presence/absence of
beaver dams. While the percent of explained variation attributable to
LOP and LSS exceeded by 5-8 times that attributable to other
variables, the effects of other variables were significant; both
intercepts and slopes were affected. The explained variance in LNaOH-P
for streams ranged from 55-87%, but was only 21% for the treatment
plant. The 95% confidence limits on the mean value of NaOH-P (X -
0.8X; X + 7X) indicate that precision generally was poor; the best
obtainable precision was X +/- 0.5X. Precision always tended to be poor
when LOP was more influential in affecting LNaOH-P than was LSS, but
but only in some cases where LSS was highly influential was precision
good.
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