Using precision temperature logs to estimate horizontal and vertical groundwater flow components

Abstract

A new method of estimating the horizontal and vertical specific discharge components of groundwater flow from precision subsurface temperature measurements is presented. Plotting the vertical temperature gradient as a function of both Z and T and then fitting a plane to the data can provide coefficients from which the vertical and horizontal groundwater specific discharge components may be estimated. Alternatively, by considering the vertical component of groundwater to be zero, it is shown that quadric or cubic fits to temperature data provide coefficients from which horizontal groundwater flow may be estimated. These expressions along with expressions previously derived to estimate only vertical, only horizontal, or both vertical and horizontal flow components are fitted to observational data from four sites and five flow zones. It is learned for these examples (using an available fitting program) that although many of the expressions fit the observational data very well statistically, those expressions which incorporate both the vertical and horizontal flow components of specific discharge must generally be constrained so that resulting parameters will provide flow estimates consistent in direction and heat transfer with available piezometer data and/or the fundamental curvature of the temperature log. Expressions incorporating only νX or only νZ can sometimes yield estimates quite different from the estimates obtained from the expressions incorporating both νX and νZ. It is concluded that an estimate of the horizontal and vertical flow components requires both consideration of the flow calculations along with available piezometric data and the fundamental curvature of the temperature log.

Possible Ambiguities in Subsurface Temperature Logs: Consideration of Ground-water Flow and Ground Surface Temperature Change

“…Sharp discontinuities in a temperature log, such as those produced by ground-water flow along a fault or horizontal layer, or water entering and leaving a borehole at different depths, are usually distinguishable (e.g., ZIAGOS and BLACKWELL, 1986;BIRCH, 1947). However, ground-water flow across a depth interval of the order of a hundred meters, having constant thermal conductivity, can result in a temperature log that is smoothly curved across the interval (e.g., REITER, 2001). The curvature resulting from ground-water flow can closely resemble the curvature resulting from ground surface temperature change.…”

Thermal log analysis for recognition of ground surface temperature change and water movements

“…This reduced noticeably the number of suitable boreholes even in areas where extensive thermal logging was performed. Conversely, hydraulic disturbances in the temperature-depth profiles recorded in boreholes can be of help in groundwater studies for the estimation of flow parameters (Reiter, 2001;Anderson 2005;Verdoya et al, 2007). Kohl (1998) made a first attempt to include also boreholes disturbed by water circulation in the climate studies by taking into account the combined effect of conductive heat transfer and advection.…”

Thermal Methods for Investigating Ground-Water Recharge

“…Studies that used thermal data to examine recharge in moderate-to-deep unsaturated zones include those of Reiter (1999Reiter ( , 2001), Izbicki and Michel (2002), Constantz and others (2003), and Dowman and others (2003). Examining unsaturated zones to depths of 100 m and saturated zones to depths of 350 m, Reiter used high-precision temperature logs to evaluate vertical moisture fluxes in the Rio Grande Rift in central and southern New Mexico.…”