Ground-Water Salinity Control Assessment Along the Canadian River--An Integrated Geophysical Approach

Abstract

Increased salinity in Lake Meredith has been attributed by water sampling to a reach of 5.5 mi of the Canadian River immediately below Ute Dam near Logan, New Mexico, as a source of saline inflow. Since Lake Meredith, impounded by Sanford Dam 150 mi downstream from Ute Dam, and the Canadian River are primary water supplies for several municipalities, including the city of Amarillo, Texas, remediation of salinity contamination is needed. Investigations performed in the late 1960s and early 1970s by the Texas Water Quality Board, the Canadian River Municipal Water Authority, and the U.S. Bureau of Reclamation conclude that the saline contamination is the result of naturally occurring artesian aquifers associated with evaporites. Proposals concluded that relieving the artesian head on these aquifers through pumping and disposing of the brine in deep-injection wells would greatly reduce the saline inflow into the river. An exploration program was initiated in November 1993 to determine the character of the brine aquifer(s), lateral extent, porosity/permeability, and also potential deep injection strata for disposal wells for the brine water. Included in this program were exploration drilling, borehole geophysics, surface seismic reflection, and pumping tests. Shallow geophysical reflection surveys in the river channel mapped the brine aquifer and located lateral discontinuities, interpreted as collapse zones providing vertical flow paths from the brine aquifer to the river channel. Deep seismic reflection surveys, tied to existing deep oil wells in the area, show sufficiently thick sedimentary sequences for deep disposal wells. These sedimentary sections of arkosic sands are associated with a deep graben in the vicinity of Logan where brine flows into the Canadian River. Log analysis of existing wells in the area allowed the correlation of lithology to seismically derived structural horizons. Information on a variety of lithologic parameters, including primary and fracture porosity, allowed selection of disposal formations prior to injection testing.