RELATING GEODETIC DEFLECTION TO STREAMFLOW DISCHARGE THROUGH STORAGE-DISCHARGE RELATIONSHIP

Climate change impacts and increasing demands for water require better methods for estimating water resources at small to intermediate watershed scales (~ 1000 km²). Here, GPS vertical deflection under hydrologic loading and streamflow discharge are analyzed in snowpack dominated mountainous watersheds to identify relationships between geodetic deflection and seasonal discharge. This study focuses on three western U.S. mountainous watersheds using publicly available GPS time series from UNAVCO and UNR and streamflow time series from USGS. We analyze vertical GPS deflections to extract the deflections associated with hydrologic loading, which we use as a proxy for changes in watershed storage at daily to weekly temporal resolution. We compare the response of streamflow discharge to GPS vertical deflection during streamflow recession periods to investigate relationships between terrestrial storage and discharge. We compare these relationships seasonally and between watersheds 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 on the watershed budget. This measurement could potentially provide unprecedented insight into the antecedent storage conditions and/or evapotranspiration which could lead to significantly improved streamflow prediction and water resource estimates.