Title: Tracers Reveal Recharge Elevations, Groundwater Flow Paths and Travel Times on Mount Shasta, California

Abstract

Mount Shasta (4322 m) is famous for its spring water. Water for municipal, domestic and industrial use is obtained from local springs and wells, fed by annual snow melt and sustained perennially by the groundwater flow system. For this study, we examined geochemical and isotopic tracers in samples from wells and springs on Mount Shasta, at the headwaters of the Sacramento River, in order to better understand the hydrologic system. The topographic relief in the study area imparts robust signatures of recharge elevation to both stable isotopes of the water molecule (δ¹⁸O and δD) and to dissolved noble gases, offering tools to identify recharge areas and delineate groundwater flow paths. Recharge elevations determined using stable isotopes and noble gas recharge temperatures are in close agreement and indicate that most snowmelt infiltrates at elevations between 2000 m and 2900 m, which coincides with areas of thin soils and barren land cover. Large springs in Mt Shasta City discharge at an elevation more than 1600 m lower. High elevation springs (>2000 m) yield very young water (<2 years) while lower elevation wells (1000–1500 m) produce water with a residence time ranging from 6 years to over 60 years, based on observed tritiummore » activities. Upslope movement of the tree line in the identified recharge elevation range due to a warming climate is likely to decrease infiltration and recharge, which will decrease spring discharge and production at wells, albeit with a time lag dependent upon the length of groundwater flow paths.« less

Authors:

Peters, Elizabeth ^[1]; Visser, Ate  ^[2];

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• Search DOE PAGES for ORCID "0000-0003-4048-4540"

Esser, Bradley ^[2]; Moran, Jean ^[1]

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+ Show Author Affiliations

1. California State Univ. East Bay, Hayward, CA (United States). Dept. of Earth and Environmental Sciences
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:

Tue Jan 23 00:00:00 EST 2018

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); California State Water Resources Control Board (SWRCB), Sacramento, CA (United States). Groundwater Ambient Monitoring and Assessment (GAMA) Program

OSTI Identifier:

1458620

Report Number(s):

LLNL-JRNL-741838
Journal ID: ISSN 2073-4441; WATEGH; 896005; TRN: US1901482

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

Water (Basel)

Additional Journal Information:

Journal Name: Water (Basel); Journal Volume: 10; Journal Issue: 2; Journal ID: ISSN 2073-4441

Publisher:

MDPI

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; recharge; isotopes; noble gas; tritium; evapotranspiration