Appraisal of streamflow in Tualatin River basin, Washington County, Oregon

This report describes the within-year time distribution of streamflow; the magnitude and frequency of annual minimum, mean, and maximum flows; and the within-year storage required to sustain selected flows in the Tualatin River basin. The report does not include an appraisal of instantaneous peak discharges in the basin. 

Data were derived by statistical methods and are adequate for general water-development planning. A duration hydrograph provides a general description of the within-year time distribution of streamflow. Generalized equations based on a sample of gaged flows are presented for estimating magnitude and frequency of flows at ungaged sites. Generalized storage relations are included for estimating storage requirements at gaged and ungaged sites.