Mean streamflows for any river can vary greatly year-by-year.

Streamflow varies by year

The table below shows the annual mean streamflow for the years 1959-2001. Annual mean streamflow is the average of all daily streamflows for the year. The long-term annual mean streamflow for the period of record is about 136 ft³/s. Variability in annual mean streamflow is shown by contrasting the wet year of 1975, when annual mean streamflow was 213 ft³/s to the dry year of 1999, when mean streamflow was 86.9 ft³/s for the dry year of 1999. Thus, streamflow during 1975 was about 56 percent above the long-term average, and streamflow during 1999 was only about 63 percent of the long-term annual average