HR: 1340h
AN: H33D-1414    [Abstracts]
TI: The utility of geologic analysis in siting new irrigation wells in the Upper Klamath Basin, Oregon, USA
AU: * Jenks, M
EM: margi.jenks@dogami.state.or.us
AF: Oregon Department of Geology and Mineral Industries, 800 NE Oregon St., Suite 965, Portland, OR 97232 United States
AB: For a number of years the Oregon Department of Geology and Mineral Industries (DOGAMI) conducted a major 1:24K mapping program in the Klamath Basin to support the hydrologic work of the Oregon Water Resources Department. In the summer of 2000, just prior to the water crisis of 2001, I mapped the Malin 1:24K quadrangle. As part of every 1:24K mapping project, the DOGAMI geologists would examine the well logs for both irrigation and domestic wells within the quadrangle boundaries. In my analysis of the well logs for wells in the Malin 1:24K quadrangle I looked particularly at the high production irrigation wells (2,000+gpm) and their locations versus the area's structural patterns and geologic stratigraphy. I noticed that the high production wells were located near the major valley-bounding faults, on their downthrown sides within the valley floor. Wells drilled to similar depths in the hills above the valley-bounding faults, or away from the faults toward the center of the valley floor, led to dry holes. From this observation came two hypotheses about the locations of high production wells in the Upper Klamath Basin: they either were intersecting the valley-bounding faults, which were carrying water, or they intersected the volcanic aquifer at a shallow depth. With the onset of the water crisis in 2001, I had the possibility of testing these hypotheses with actual new well site locations. I helped both the local irrigation districts, and private farms and ranches, to site 24 wells. My targets were either the valley-bounding faults, or highs in the basement volcanic rocks underlying the valleys. Out of these 24 wells, eighteen were high production wells or reached the owner's projected production target, two were moderate producers, and four did not produce water in the quantities needed for irrigation. Thus, hypotheses, derived from a close observation of and correlation between the geology and the well logs, were useful in raising the success rate in siting high production irrigation wells in this basin.
DE: 1832 Groundwater transport
DE: 1842 Irrigation
DE: 5480 Volcanism (6063, 8148, 8450)
SC: Hydrology [H]
MN: Fall Meeting 2005