Discussion
In general, water quality decreased as the river moved through the
Denver metro area, which seems to imply that in this system, urban
hydrology, especially impervious surfaces and engineered drainage, may
be influencing the river. In addition to a general decrease in water
quality through the study area, we also noted several hotspots of
severely degraded water quality. The data also shows strong seasonality
in water quality, with higher concentrations of nutrients and higher BOD
in the winter months.
Water quality generally decreased through the Denver metro area.
Specifically, DO decreased (Figure 5); the concentrations of
orthophosphate (Figure 8) and ammonia-N (Figure 6) increased; and BOD
(Figure 4) and temperature (Figure 9) increased from the 0 km site to
the 63 km site (p < 0.05). Nitrate-N did not show the same
overall trend of increasing concentration (Figure 7), but this is
primarily because the 14 km and 19 km sites had excessively high
concentrations. However, compared to the 0 km site (the control point),
nitrate-N concentrations were elevated at all sites within the city.
Compared to the other parameters measured, pH seems to be more variable
and does not display a distinct trend (Figure 10). All of the measured
pH values were between 6.2 – 8.9, although overall, they tended to be
slightly basic.