Stable isotopes of recharge to the alpine epikarst landscape of the wasatch mountains, Utah USA

Abstract

Abstract Study Region This study considers the hydrogeology of alpine epikarst by deciphering the controls on water isotopes from pools in the Timpanogos Caves and the American Fork River in the Wasatch Mountains of central Utah. Study Focus From prior research in the Timpanogos Caves, recharge to some cave pools is via diffuse flow through the fractured rock matrix. Other pools receive recharge by direct infiltration through the epikarst above the cave either by open fractures or by piston flow through an epikarst reservoir. Herein, δ18O and δ2H from water samples collected in 2012 from five cave pools yield connections to the source elevations of recharge in the overlying alpine epikarst, despite the cave pools having similar elevations. New Hydrological Insights for the Region Regardless of the recharge mechanism, δ18O and δ2H values vary between the peak recharge season in April–May and a peak evaporation season from June–August, result from seasonal changes in precipitation source, freeze-thaw cycles, and sublimation of snow prior to melt and infiltration. By ascribing likely elevations to the sources of recharge, based upon epikarst geometry and supporting geochemical evidence, we demonstrate that values of δ18O and δ2H vary along an altitude lapse rate of -4.8‰/km for δ18O and -35.7‰/km for δ2H.