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

Authors' Names

Noah B. ClaytonFollow

Presentation Type

Oral Presentation

Category

STEM (science, technology, engineering, mathematics)

Abstract/Artist Statement

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.

Personal Statement

As human populations continue on a path of exponential growth, consumptive demands of water resources are increasing while storage of surface and groundwater reservoirs are decreasing at rates faster than they can be naturally replenished. The ability to accurately estimate and monitor available water from seasonal precipitation is of paramount importance to water resource management. Given the onset of climate change, uncertainties such as long periods of drought and/or increased frequency of flooding events are potential hazards of great concern. In the last decade, evidence of increasing intensity of precipitation events support the contention that aspects of the hydrological cycle are intensifying in response to global climate warming. These issues underscore the importance of increasing our understanding of the interactions between physical mechanisms and processes that enable us to measure water storage changes. Terrestrial water storage in a watershed includes snowpack, surface water, water contained in the biosphere, soil moisture, and groundwater. Storage is a term that sounds static but in reality, the water is always in a state of transport moving through the watershed system at various velocities regulated by encountered resistance due to watershed characteristics such as climate, topography, vegetation, lithology, infiltration capacity, hydraulic conductivity, and local geological structure that govern residence times in watershed systems. In periods where there is minimal precipitation and evapotranspiration, stream discharge has been related to groundwater storage and the storage-discharge relationship is a well adopted theory in hydrology. Over the last decade, surface deformation studies using geodetic time-series (GPS) have consistently shown seasonal signals associated with the elastic response of the Earth’s crust under seasonal hydrologic loading (eg. snowpack). These GPS vertical deflections have been used to estimate changes in terrestrial water storage on large regional scales. Thus, seasonal changes in terrestrial water storage have been independently related to both streamflow discharge and vertical geodetic displacement. The objective of this project is to investigate and explore the relationship between stream discharge and GPS deflection through the lens of the storage-discharge relationship. This effort will improve our understanding of the interactions between hydrological processes and surface deformation and has the potential to significantly increase the predictive power of water resources management when estimating annual water resource availability, drought, and potential flooding events.