Correlations of Oklahoma Stream Temperatures with Air Temperatures

Air temperatures are sometimes used as substitutes for stream temperatures. To examine the errors associated with this substitution, linear relationships between 38 Oklahoma stream water temperature records and associated air temperature records were analyzed. Weather monitoring stations were, on average, 53.5 miles from the stream stations. From the lumped data set (38,859 data pairs), the general equations, Tw=O.787Ta+5.49, Tw=O.829Ta+4.67, and Tw=O.898Ta+3.47, with temperatures in degrees Celsius, were derived for daily, weekly, and monthly mean stream temperatures Tw, respectively. Mean yearly stream temperatures were also used, but the results proved to be inconclusive. Standard errors of prediction between all measured and predicted stream water temperatures in Oklahoma were 3.22DC (daily), 2.66DC (weekly), and 2.06DC (monthly). Separate analyses for individual stream gaging stations gave lower standard errors of prediction. The measured water temperatures follow the annual air temperature cycle closely. No time lags were taken into account, and periods of air temperatures below ODC were excluded from the analysis. The model is used to project water temperature increases in response to air temperature increases which may occur if climate changes due to a doubling of atmospheric carbon dioxide.National Agricultural Water Quality Laboratory, US Department of Agriculture; Mid-continent Ecology Division, US Environmental Protection Agenc