Upper Colorado River Basin streamflow, March-August 2023

March-August daily average streamflow for the last 30 years (1991-2022) (dark gray lines) compared to 2023, showing the periods where 2023 streamflow was above (blue) and below (orange) the historical average. Individual years of the relevant historical streamflow period are shown in light gray. 

These Upper Colorado River Basin gages show that streamflow during the 2023 water year was consistently above the 30-year average and even surpassed the previous 30-year record for brief periods in the spring at three of the four selected gages. These data indicate a wetter than normal streamflow year compared to the 30-year averages. However, looking at the historical individual-year hydrographs shown in light gray, it’s not unusual to have a year of high flows – even higher than 2023 during the 30-year preceding period. 

This illustration is a part of the Colorado River Basin Drought and the 2023 Water Year geonarrative.