T162 Hydrogeology in Support of Integrated Water Management

Tuesday, 24 September 2024
8:00 AM - 12:00 PM
211A

INSIGHTS INTO THE HYDROLOGICAL BALANCE OF BEAR LAKE (UTAH-IDAHO) THROUGH STABLE WATER ISOTOPE ANALYSIS

Paper number: T162-6
Program: Technical Sessions
Time: 9:15 AM – 9:30 AM

Authors

Abstract

Bear Lake, situated on the border of Utah and Idaho within the northeastern Great Basin, is an important freshwater reservoir for agriculture and hydropower, in addition to being a recorder of climate change in the western United States. Estimating the components of its hydrological balance, specifically evaporation, has been limited due to inconsistencies and uncertainties across existing methods. An effective and efficient way to quantify processes that regulate lake levels is needed to improve the management of water resources in drought-prone regions such as the western United States, especially in the context of climate change.

In this study, we utilize the stable isotopes of water (δ18O, δ17O, and δ2H) to construct an isotopic mass balance model of Bear Lake, constrain its evaporation rate, and assess its sensitivity to climate parameters such as temperature and humidity. The datasets used come from measured isotopic data from sampling campaigns in 2022 and 2023, combined with existing geochemical and hydrological data from community databases and gauge stations. The δ18O and δ2H values were analyzed following the classic Craig-Gordon isotopic mass balance model to derive an evaporation rate of 2.18 x 108 m3/yr (± 2.26%, 1σ using δ18O; ± 1.59%, 1σ using δ2H).

We leverage published isotopic data from lake cores to infer lake isotopic composition in the past and test the model's response to different environmental conditions. This approach provides insights into the past, present, and future hydroclimate of the study area. Furthermore, we will present new δ17O measurements, allowing for the calculation of deviations from the regional meteoric water lines in the Δ17O parameter. Δ17O is humidity and evaporation-sensitive analogous to d-excess. This sensitivity will allow us to put better constraints on the uncertainty of the calculated evaporation rate and humidity together. Ultimately, the objective of this study is to demonstrate the value of monitoring modern water isotopic composition to supplement interpretations of carbonate-based paleoclimate datasets and inform current and future management of water resources.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-403368

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