Climatic and streamflow estimates for northeastern Utah

Abstract

This report shows how information from 44 air-temperature, 59 precipitation, and 86 streamflow sites was converted to a common-time base of 1941-70, and how general relations were developed to extend the converted point values to unsampled sites. Two methods, regression and ratio, were used to convert the data to a common-time base. Both methods require a period of concurrent data at two sites. After an estimating equation has been defined from concurrent data, the regression method requires data at the independent site only during the record voids of the dependent site. The independent site must have a complete record, however, if the ratio method is to be used. Regression techniques were used to fill voids in the air-temperature data base and to determine the correlation of monthly and annual averages, the average annual distribution, and equations that can be used to estimate average monthly and seasonal air temperature, precipitation, and streamflow. Incomplete precipitation and streamflow records were adjusted to the 1941-70 average on the assumption that the ratio of con- current data is directly proportional to the ratio of the respective 1941-70 average annual values at nearby sites. The average monthly air temperature at a short-term collection site generally can be approximated with a standard error of estimate of less than 2 degrees Fahrenheit (1.1 degrees Celsius). The standard deviation of the precipitation residuals, about the averages of the estimates for all incomplete-record sites, is 0.42 inch (11 millimetres). The average annual precipitation at the 59 sites used in this analysis is 16.2 inches (411 millimetres). Two-thirds of the streamflow estimates are within 13.0 cubic feet per second (0.37 cubic metres per second) of the averages of the site estimates, which is about 10 percent of the sample average. Altitude and location can be used to estimate the average annual temperature and precipitation. Schematic diagrams, plotted by computer, were prepared to show variations of altitude, temperature, and precipitation. Maps, also plotted by computer, show lines of equal altitude, precipitation, and temperature. Average annual streamflow can be estimated on the basis of drainage area and the average annual precipitation. Equations for these estimates have standard errors of estimate ranging from 30 to 125 percent.