Movement and Age of Ground Water in the Western Part of the Mojave Desert, Southern California, USA

By John A. Izbicki and Robert L. Michel




Water–Resources Investigations Report 03-4314

Sacramento, California 2004

Prepared in cooperation with the
Mojave Water Agency

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    Tritium and carbon-14 data in water from wells in the Mojave River and the Morongo ground-water basins in the western part of the Mojave Desert show recent recharge focused in the floodplain aquifer along the Mojave River. Older ground water was present in parts of the regional aquifer that surround and underlie the floodplain aquifer. Movement of water between the floodplain and the regional aquifers occurs near on the upgradient side of faults as water from the regional aquifer discharges to the floodplain aquifer and on the downgradient side of the faults where water from the floodplain aquifer recharges the regional aquifer. On the basis of carbon-14 ages, corrected for mineralogic reactions with aquifer materials, water from some wells was recharged more than 20,000 years ago. Geochemical data show ground-water recharge has gradually decreased as the climate changed since that time.




Purpose and Scope

Background and Previous Studies


Carbon-14 and Carbon-13

Sample Collection and Analyses



Mojave River Ground-Water Basin

Morongo Ground-Water Basin


Carbon-14 and Carbon-13

Areal Distribution of Carbon-14 Activities

Carbon-14 Activities Along Selected Geologic Sections in the Mojave River Basin

Sections A-A', B-B', and C-C'

Section D-D' and E-E'

Interpretation of Ground-Water Age Along Selected Flow Paths

Initial Carbon-14 Activity

Geochemical Reactions

Interpretation of Carbon-14 Ages Along Selected Flow Paths

Flow Path 1: Surprise Spring Basin

Flow Path 2: Upper Part of the Mojave River Basin to the East of the Mojave River

Flow Path 3: Upper Part of the Mojave River Basin to the West of the Mojave River

Limitations on Carbon-14 Interpretations



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