Extension of streamflow records in Utah

Abstract

This report provides long-term data on streamflow at selected short-term gaging stations in Utah. The records of streamflow at the short-term or secondary gaging stations are extended on the basis of a graphical correlation with concurrent records at long-term or primary gaging stations. The data presented consist of records of runoff at the short-term stations summarized on a monthly and yearly basis; these data include the actual short-term records and the correlative estimates of runoff. Methods and information are included to enable the reader to make further extensions of runoff records. The standard error of estimate for correlations used is 30 percent or less, and the coefficient of correlation is at least 0.8. Streamflow information is thereby obtained that is believed to be more representative of the long-term runoff than is an actual short-term record. This study shows that the optimum period of concurrent record needed in Utah for a reliable correlation is about 15-20 years. Extensions of record for low-flow and flood-frequency studies usually cannot be obtained from correlations. Much of this information could be collected economically by converting short-term stream-gaging stations to partial-record stations after a satisfactory correlation with a long-term station has been obtained.