Runoff in the Upper Colorado river basin, water years 1983-85, and comparisons with forecasts of runoff to Lake Powell

Runoff in the Upper Colorado River Basin was unusually great during water years 1983-85. Measured runoff to Lake Powell during 1984 was only 0.3 percent less than the record measured runoff in 1917. The runoff for 1983 ranks third, and the 1985 runoff ranks seventh largest since 1914. The combined 2-year runoff for 1983-84 was a record. Recurrence intervals for peak discharges were generally less than 100 years, while recurrence intervals for volumes of 30 days or more exceeded 100 years at several gages in 1983 and at numerous gages in 1984. The virgin flow equaled that for 1917 and tied for second and third largest since 1895. Errors in the 1983 forecasts of runoff to Lake Powell were records, but the 1984 and 1985 forecasts were more accurate.