Stream Flow Variability and Timing of a Regional Ephemeral Stream in Northern Arizona

The Rio de Flag is an ephemeral stream that flows through Flagstaff, Arizona, flowing less than 10% of the year due to geology and climate. Seasonal flows can occur during snowmelt periods and occasionally during short duration intense summer monsoon storms. With multiple regional, and local, flood control plans for the channel, it is important to understand flow characteristics including annual water volume, flow timing, and spatial and temporal trends in surface water availability. This study examines the springtime (February to May) stream gauge data from six stream gauges within the Rio de Flag, and three tributaries (Clay Avenue, Spruce, and Sinclair Washes) between 2019 and 2023. Analyses included existing gauge data to determine seasonal flow, runoff per area, and understand the relationship of snowmelt and discharge for these selected stream reaches. This study aims to gain a better understanding of ephemeral flow variability in northern Arizona and the surrounding southern Colorado Plateau to inform stream management as well as provide baseline data for understanding the impacts flow variability on riparian ecosystems.