New Mexico Geological Society Annual Spring Meeting — Abstracts

Geophysicists have recognized the potential for ground-water movement to disturb the conductive geothermal gradient and to therefore pertub measurements of terrestrial heat flow. Conversely, one may examine deep precision temperature logs not only to evaluate heat-flow data, but also to study the hydrologic regime of an area. By plotting Q (heat flow) vs T (temperature) the direction and magnitude of vertical ground-water movement may be estimated. The slope of the Q-T plot is given by m = v / pc, where v is specific discharge, p is density, and c is specific heat.

Using both heat-flow data, and data on hydraulic head differences between formations, estimates of specific discharge have been compared at 8 locations in the San Juan Basin. Estimates of the direction of vertical ground-water movement (up or down) using the two techniques were compatible at many of the sites, and the rates of specific discharge also agreed to an order of magnitude. At some locations the different estimates of vertical specific discharge were incompatible, probably because of poor thermal conductivity data (needed to calculate heat flow)
and incomplete hydrologic data. The deeper heat-flow data in the San Juan Basin demonstrate smaller Q-T slopes; and therefore indicate lower rates of specific discharge. Q-T plots may have the potential to provide valuable estimates of the magnitude and direction of vertical ground-water movement in many areas.