Residence time of groundwater issuing from the South Rim Aquifer in the eastern Grand Canyon

Author

Jim Fitzgerald, University of Nevada, Las Vegas

Award Date

5-1996

Degree Type

Thesis

Degree Name

Master of Science in Geoscience

Department

Geoscience

First Committee Member

David K. Kreamer, Chair

Second Committee Member

Jean S. Cline

Third Committee Member

Kevin H. Johannesson

Graduate Faculty Representative

Vernon F. Hodge

Number of Pages

111

Abstract

In the eastern Grand Canyon, secondary porosity created by north trending faults, folds, and breccia pipes, facilitates groundwater flow through the South Rim carbonate aquifer. Springs associated with the South Rim Aquifer have low ³H concentrations, [Ca²⁺]/[Mg²⁺] rations close to unity, and variable uranium concentrations. For a geochemical comparison, springs are subcategorized on the basis of geology and discharge. Type I springs are associated with high-angle normal faults and have high discharge rates. These springs discharge Ca²⁺ - Mg²⁺, HCO₃^- waters, have ³H concentrations <2 TR, and ²³⁴U/²³⁸U activity ratios >3 AR, which suggest long groundwater residence times. Type II and IV springs are located on canyon mesas and have low discharge rates. These springs are predominantly Ca²⁺ - Mg²⁺, SO₄^2- waters, have tritium ratios between 1 and 6 TR, and ²³⁴U/²³⁸U activity ratios between 1 and 2 AR. Higher ³H and ²³⁸U concentrations and low ²³⁴U/²³⁸U activity ratios in the latter waters may be due to shorter groundwater residence time. Based on ³H concentration, the occurrence of dedolomitization, and the resultant uranium isotope fractionation in groundwater, the minimum residence time of water discharging from the South Rim Aquifer is indicated to be > 40 years.

Keywords

Arizona – Grand Canyon; Aquifers; Groundwater flow; Groundwater recharge; Springs

Disciplines

Geochemistry | Hydrology

File Format

pdf

Degree Grantor

University of Nevada, Las Vegas

Language

English

Comments

Signatures have been redacted for privacy and security measures.

Repository Citation

Fitzgerald, Jim, "Residence time of groundwater issuing from the South Rim Aquifer in the eastern Grand Canyon" (1996). UNLV Theses, Dissertations, Professional Papers, and Capstones. 1426.
http://dx.doi.org/10.34917/3347466

Rights

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