14 Hydrogeology of Alluvial Aquifers in the Western U.S.

Friday, 29 April 2005
1:10 PM - 3:20 PM

HYDROGEOLOGIC AND LEGAL FEASIBILITY OF REMOTE EXTRACTION FROM A GROUNDWATER BASIN

Paper number: 14-7
Program: THEME SESSIONS
Time: 3:00 PM – 3:20 PM

Authors

Abstract

Unsuccessful attempts by well drillers to construct four groundwater wells on a 40-acre ranch in Ventura County, California (Property) resulted in the completion of very low producing (<2 gpm) water wells with poor water quality, water wells with crude oil, and abandoned pilot holes due to oil, gas, and limited drilling equipment. Underlying the Property, Miocene rocks have been thrust over a sequence of Quaternary strata along the shallowly dipping, locally northeast-trending (070/40N) San Cayetano Fault. Numerous oil exploration and production wells define the effective base of fresh water in the footwall sediments and partially consolidated strata at over 8,000 feet in the defined groundwater basin, whose northern terminus has been mapped as the surface expression of the San Cayetano Fault and the base of the hillside south of the subject Property. The San Cayetano Fault underlies the Property at depths of 700 feet in the southeast and over 3,000 feet in the northwest. Fresh-water-bearing aquifers, which correlate to known high-production, acceptable water quality zones to the south, underlie the San Cayetano Fault. Thus, it is hydrogeologically feasible to drill vertical wells through approximately 1,000 feet of Miocene rock to target aquifers at depths between 800 and 2,000 feet below the Property.

In California, groundwater use is governed by the doctrine of “correlative rights and reasonable use,” which, similar to riparian rights, gives overlying property owners a common right to the “reasonable, beneficial use” of basin supply on the overlying land. In simple terms, this means that groundwater uses are limited to extracting only the amount necessary for the reasonable, beneficial uses of overlying property, which, typically, occur with the same surface and/or subsurface jurisdictional boundaries. However, when a property is outside of the legally delineated groundwater basin can that property's owner still extract groundwater from underlying aquifers that may correlate to those in the nearby basin free from the constraints and obligations imposed by the basin's management entity?

Reverse faults of various dip angles bound numerous groundwater basins worldwide. Where hydrogeologically and legally feasible, extraction of groundwater from footwall aquifers may alleviate some of the problems associated with hill and mountain development.