Linking geomorphological and environmental indices with ground-based and airborne geophysical data to upscale bedrock properties of mountainous watersheds

Thursday, 13 June 2019: 13:30
Davie West Building, DW103 (Florida Atlantic University)
Sebastian Uhlemann1, Baptiste Dafflon1, Burke J Minsley2, Craig Ulrich1, Patrick McClure3, Haruko Murakami Wainwright4, Kenneth Hurst Williams1 and Susan Hubbard1, (1)Lawrence Berkeley National Laboratory, Berkeley, CA, United States, (2)USGS Geology, Geophysics, and Geochemistry Science Center, Denver, CO, United States, (3)Lawrence Berkeley National Laboratory, Berkeley, United States, (4)Lawrence Berkeley National Lab, Berkeley, CA, United States
Abstract:
Watersheds act as integrators of a range of terrestrial processes that are affected by climate change, more frequent severe weather phenomena, and a general change in land-use. This is not only impacting upon the local hydrological, biological, and geochemical functioning of mountainous watersheds, but cascades further downstream, affecting water availability, carbon cycling, and nutrient and metal loading. Yet, this functioning and the related dynamics remain poorly understood. To address this uncertainty, the Watershed Function Scientific Focus Area (SFA) is developing a predictive understanding of how mountainous watersheds retain and release water, nutrients, carbon and metals. Focused on the East River, CO mountainous headwaters catchment, the SFA is developing understanding and tools to measure and predict how droughts, early snowmelt, and other perturbations impact downstream water availability and biogeochemical cycling at episodic to decadal timescales.

A critical aspect to reducing this uncertainty is quantifying the influence of bedrock on subsurface flow and transport over a range of space and time scales, and the associated impact on downgradient water availability and water quality. We present an approach linking detailed geophysical studies, conducted within subsystems of the East River watershed, with geological, wellbore, airborne Electromagnetic (AEM), and remote sensing data to obtain a watershed-scale understanding of the physical properties of the subsurface. The local geophysical and wellbore data highlight strong variability of bedrock properties within the watershed. This variability is also evident in the AEM data, which show a strong gradient from subalpine to montane environments. This is in agreement with hydrological monitoring and modelling data, confirming the link between geophysical data and subsurface flow properties. We investigate the relationship between the local and regional geophysical data with geomorphological and environmental indices, aiming at extrapolating our local-scale insights to the watershed scale. This will allow us to address the SFA objective of quantifying distributed bedrock-through-canopy responses to perturbations, and how these responses aggregate to a cumulative downgradient discharge-concentration signature.

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