Relating Geodetic Deflection Under Hydrologic Loading to Stream Discharge Through Storage-Discharge Relationships

Abstract

Relating Geodetic Deflection Under Hydrologic Loading to Stream Discharge Through Storage-Discharge Relationships Noah Clayton, MA Geosciences Candidate Dr. W. Payton Gardner, University of Montana Dr. Hilary Martens, University of Montana Climate change impacts and increasing demands for water require better methods for estimating water resources at small to intermediate watershed scales (~ 1500 km2). In this study, we analyze relationships between GPS vertical deflection under hydrologic loading and stream discharge to investigate temporal changes in terrestrial water storage in watersheds with strong seasonal hydrologic events. Using publicly available GPS time series from UNAVCO and UNR and stream discharge time series from USGS, we isolate vertical GPS deflections resulting from hydrologic loading, use that deflection as a proxy for changes in watershed storage with daily to weekly temporal resolution, and investigate relationships between terrestrial water storage and discharge during streamflow recession periods. We compare terrestrial water storage inferred through conventional storage-discharge relationships to GPS measurements as a proxy for changes in storage to develop knowledge of the spatial and temporal patterns of storage and discharge in our studied watersheds. Our results indicate that geodetic deflection can potentially be used as a fundamental constraint of the watershed’s hydrologic behavior. The geodetic deflection measurement provides unprecedented insight into the antecedent storage conditions and/or evapotranspiration which could lead to significantly improved streamflow prediction and water resource estimates