An analysis of the relationship between air and stream water temperature
records for 11 rivers located in the central United States was conducted. The
reliability of commonly available water temperature records was shown to be
of unequal quality. Simple linear relationships between air (Ta) and water
(Tw) temperatures were developed for daily and weekly average temperatures
and showed some level of accuracy, especially for weekly average temperatures
and for small streams. The general equations Tw:= 5.0 + 0.75 Ta and
Tw = 2.9 + 0.86 Ta simulated the daily and weekly temperatures of the 11
streams studied with a standard deviation between measurements and
prediction of 2.7· C and 2.1° C, respectively. Predictions were better for
shallow streams than for deep streams. Better predictions were obtained with
equations derived for each specific stream individually. Time lags between
water and air temperatures ranged from hours to days. In first approximation,
the lag time between water temperature response to air temperature changes is
found to be proportional to average water depth. For a 2 ft deep stream, it
is on the order of hours, for a 15 ftdeep river it is on the order of days.
Taking into account these time lags slightly improved daily water temperature.
predictions. Periods of ice cover were excluded from the analysis.
Environmental Research Laboratory, US Environmental Protection Agency
Preud'homme, Eric B.; Stefan, Heinz G..
Relationship Between Water Temperatures and Air Temperatures for Central U.S. Streams.
St. Anthony Falls Hydraulic Laboratory.
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