Dear Colleagues,

We are pleased to announce our first seminar for our series, hosted by the International Association of Geodesy (IAG) Working Group 3.1: Hydrologic Signature in Geodetic Observations, will be given by Matthew Swarr, from the University of Montana.  This seminar wil be held at 11:00 EDT/ 8:00 PDT/ 16:00 CET/ 23:00 CST.

https://iu.zoom.us/j/82295302430

Meeting ID: 822 9530 2430

Title: Tracking Mountain Aquifer Storage and Discharge Using Space Geodesy

Abstract: Fractured bedrock underlying mountain ranges is a critical source of water for mountain and adjacent low-elevation communities and ecosystems. Despite the importance of mountain groundwater systems to water supplies of major socioeconomic regions, quantifying storage changes within these aquifers remains a challenge. To evaluate the fate of water stored in mountain systems and the role of extreme precipitation events, such as atmospheric rivers, in replenishing groundwater storage, we use high-precision Global Navigation Satellite Systems (GNSS) surface displacements to constrain changes in groundwater storage within the Sierra Nevada and Cascade mountain ranges, two important mountainous regions of the Western United States. We find that mountain aquifers have been significantly depleted over the past two decades, associated with recurrent severe multi-year droughts within these regions. However, extremely wet winters, can replenish storage by more than twice the average annual flux over relatively short periods, driving the state of groundwater storage from historical lows to above normal conditions. Further, we find GNSS derived groundwater storage changes are strongly correlated with observed groundwater head from wells. These findings show that periods of extreme precipitation rapidly recharge mountain aquifer systems and can offset multi-year losses. Moreover, mountain aquifer systems can retain storage gains for several years post-event, providing a durable source of streamflow, agricultural, and municipal water supply. As extreme precipitation events are predicted to become more intense and frequent in coming years, we hypothesize that these events may help offset groundwater loss due to aridification, sustaining ecosystems and buffering against a new, drier climate normal. Additionally, we provide insights on a newly developed method to constrain the hydraulic properties of mountain groundwater systems at the mountain range-scale using fluid diffusion models in combination with our GNSS-inferred estimates of groundwater storage. Our results indicate the effective hydraulic conductivity of the bedrock within the Sierra Nevada and Cascades is an order of magnitude higher than previous findings, and we find consistency between our estimates of the average groundwater flow path length within the Sierra Nevada and Cascades and those derived from perennial and intermittent and perennial stream networks, respectively, indicating the Cascades to be a recharge dominated groundwater system with increased regional groundwater flow compared to the Sierra Nevada. These results further the current understanding of the storage and release properties of mountain groundwater systems as well as highlighting the use of geodetic observations in advancing groundwater hydrology.