T160 Status of the Headwaters in our Changing World: Springs and Base Flow

Tuesday, 24 September 2024
8:00 AM - 12:00 PM
210C

ALPINE KARST OF SILVERTIP MOUNTAIN, BOB MARSHALL WILDERNESS, MONTANA

Paper number: T160-3
Program: Technical Sessions
Time: 8:20 AM – 8:35 AM

Authors

Abstract

Mountains are often referred to as the “water towers” of the world due to their ability to store vast amounts of water in the form of snow and ice, sustaining downstream ecosystems and populations through seasonal meltwaters. Despite their critical role in maintaining base flow, the significance of groundwater and ground ice reservoirs in mountain hydrology has only recently been acknowledged. Even small alpine karst aquifers can store substantial water volumes, contributing disproportionately to downstream base flow. However, limited field data and high heterogeneity impede the current understanding of groundwater storage dynamics in alpine karst. This study examines the contributions of different water storage components to discharge at the outlet spring(s) in the alpine karst of Silvertip Mountain, Bob Marshall Wilderness, Montana.

We continuously monitored water temperature and stage height at three sites within the Silvertip System from July 2021 to August 2023 to examine flow patterns and response to changing meteorological conditions. Additionally, we collected hydrologic data and water samples for solute and isotopic analysis to characterize the chemistry of surface and subsurface waters on the mountain. Continuous data show seasonal and diurnal fluctuations in stage, while water temperature shows seasonal patterns. Stage and temperature both respond rapidly to rain events, melting, and freezing. Preliminary cross-correlation analysis suggests that interactions among air temperature, solar radiation, and relative humidity—proxies for melting, transpiration, and evaporation—control daily fluctuations in discharge. Solute and C isotope analyses, together with solute speciation modeling, indicate that groundwater chemistry reflects meteoric recharge modified by carbonate weathering, as expected. Water isotope analyses indicate some fractionation during recharge by sublimation and/or evaporation, though the trend varies from year to year. Alpine environments are particularly susceptible to the impacts of climate change, which can dramatically alter mountain hydrology. Results of this study highlight the influence of changing meteorological conditions on water storage dynamics in an alpine karst system, providing valuable insight into the long-term effects of climate change on downstream water availability and ecosystem health.

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

doi: 10.1130/abs/2024AM-405204

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