3 Geomorphological, Hydrologic, and Geothermal investigations of basin aquifers in Baja California Sur (BCS), Mexico
The session will explore BCS basins, focusing on groundwater storage, evaporation, runoff and transport mechanisms, featuring experts on thermal and shallow groundwater interactions, soil mapping for hydrological planning, geomorphology, and human impacts on water balance.
Wednesday, 22 April 2026
8:00 AM - 12:00 PM
LMH, Isla Carmen
How the Geologic Framework and Incidental Recharge Affects the Deschutes Basin Groundwater Flow System near Redmond, Oregon - Clues from Redmond Well #9
Paper number: 3-5
Program: Technical Sessions
Time: 9:05 AM – 9:20 AM
Authors
Abstract
The Deschutes basin groundwater flow system originates in the Quaternary Cascade Range, flows northeast beneath an area of little natural recharge and through upper Miocene and Pliocene deposits of the Deschutes Formation. A sharp permeability contrast with lower permeability Miocene-Oligocene volcanic deposits of John Day Formation redirects groundwater flow northward and towards a deep canyon incised by the Crooked River.
Redmond Well #9, a 240-m deep municipal well drilled into the Deschutes Formation located 6.4 km south of the nearest exposure of the John Day Formation has upward groundwater flow from the base of the borehole at 656-m above mean sea level (amsl) that exits the borehole at an elevation of about 774-m amsl; 46-m below the 820-m static water-level in the well. Water-bearings strata in the well are low-K tholeiitic lava flows that underlie the 6-Ma Osborne Canyon Ignimbrite, and the water has a specific conductance of 125 μS/cm.
Virtually all surface water gains in the Crooked River Canyon are where low-K tholeiitic lava flows that underlie the Osborne Canyon Ignimbrite are exposed, and account for 31 m3/s of groundwater contributions to a 13-km reach from above Osborne Canyon to Opal Springs. The specific conductance at Opal Springs is 128 μS/cm.
The 46-m increase in hydraulic head in Redmond Well #9 is from over one hundred years of incidental recharge from leaking canals and on-farm losses, adding an annual mean of about 11-14 m3/s to the groundwater flow system. Surface water measurements taken since irrigation diversions began show base flow now begins much farther upstream above about 841-m amsl elevation in the Crooked River. Hydraulic heads in wells are up to about 853-m amsl in the same area. Specific conductance of groundwater in wells less than 122-m deep near Redmond average above 300 µS/cm.
Permeable low-K tholeiitic lava flows adjacent to the John Day Formation are a principal path for regional groundwater flow and discharge to the Crooked River. Water in the lower part of Redmond #9 is regional groundwater. Groundwater above the permeable zone at 774-m amsl is geochemically distinct from the lower regional groundwater, and much of the head difference between the 820-m amsl static water level and the permeable zone at 774-m stems from incidental recharge.
Geological Society of America Abstracts with Programs. Vol. 58, No. 3
doi: 10.1130/abs/2026CD-410767
© Copyright 2026 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.