Detecting Streamflow in Dryland Rivers Using CubeSats.

Determining the flow regime of non-perennial rivers is critical in hydrology. In this study, we developed a new approach using CubeSat imagery to detect streamflow presence using differences in surface reflectance for areas within and outside of a river reach. We calibrated the approach with streamflow records in the Hassayampa River of Arizona over 3 years (2019-2021), finding good agreement in the annual fractions of flowing days at stream gages (  = 0.82,  < 0.0001). Subsequently, annual fractions of flowing days were derived at 90 m intervals along the Hassayampa River, finding that 12% of reaches were classified as intermittent, with the remaining as ephemeral. Using a Hovmöller diagram, streamflow presence was visualized in unprecedented spatiotemporal detail, allowing estimates of daily fraction of flowing channel and annual fractions of flowing days. This new tool opens avenues for detecting streamflow and studying hydrological and biogeochemical processes dependent on water presence in drylands.