Intermittent and Perennial Streamflow Regime Characteristics in the Okanagan

Streamflow data from ten Water Survey of Canada gauging stations were analyzed to characterize streamflow regimes in the Okanagan Basin (British Columbia). The differences in the streamflow regime characteristics of the perennial and intermittent streams were subtle, except for the obvious difference in summer low flows. The intermittent streams tended to have faster recessions after spring freshet, steeper flow duration curves, a slightly earlier median day of the year of the start of the freshet, and more variable discharge in fall. In years with high fall precipitation, discharge was also high during fall for the intermittent streams but in other years it was very low. Discharge on August 15th was lower or similar to streamflow on March 15th for the intermittent stream, whereas it was much higher on August 15th for the perennial streams. These subtle streamflow regime differences point to differences in flow pathways, groundwater contributions to streamflow, and residence times between the intermittent and perennial watersheds, and may have important ecological implications.