Modeling Diurnal Fluctuations in Stream
Temperature and Dissolved Oxygen
A. D. KARTCHNER, Assistant Professor
N. DIXON, Associate Research Engineer
D. W. HENDRICKS, Associate Professor
Utah Water Research Laboratory
Utah State University
Logan, Utah
INTRODUCTION
During the last three years, a project at the Utah Water Research Laboratory has
been developing a simulation model for the hydrology and water quality of the Little
Bear River, a small mountain valley river system in northern Utah. Though a monthly
time increment was used in the basic simulation model, two water quality parameters,
temperature and dissolved oxygen, exhibit diurnal fluctuations and therefore require
an hourly time incrementation.
The two objectives of this paper are: 1) to illustrate the characteristics and
possible implications of these diurnal fluctuations in small rapidly flowing streams,
and; 2) to present two alternative techniques of analysis by which these variations
may be represented.
Daily variations in water temperature and dissolved oxygen (DO) concentration
in natural streams are recognized as significant and have been reported by several
observers. Hoak and Bramer (1) found relatively minor diurnal variations in dissolved
oxygen in several Pennsylvania streams. Gunnerson and Bailey (2) report significant
daily variation in DO concentration along the Sacramento River from Redding to the
delta. O'Connell and Thomas (3), in reporting their studies of the Truckee River in
Nevada, indicate relatively large diurnal cycles occurring in their dissolved oxygen
data. These fluctuations were attributed to the activity of photosynthetic organisms
attached to the stream bottom.
Thomann (4) found no evidence of diurnal fluctuations in temperature along
the Potomac Estuary. Daily variations in DO were reported only at the most upstream sampling point, which was above the zone of tidal influence.
Macan (5) studied daily patterns of temperature fluctuation in a small English
stream. He found large diurnal variations during spring months with less evidence of
this phenomenon the rest of the year. Smaller extremes were observed on stormy or
cloudy days.
Despite the fact that DO and temperature fluctuations do occur on almost all
natural streams, little has been reported concerning characterization of this phenomena
or its utilization in assessing stream water quality.
When daily variations do occur, their effect upon the biotic community of the
stream could be important. Doudoroff and Warren (6) found that the growth rate of
fish subjected to fluctuating DO were dependent upon the minimum concentration
rather than the mean value. The effect of fluctuating DO levels on growth was found
to be comparable to a constant level at about one mg/1 higher than the minimum
concentration.
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