Dipole Probe: Design and Field Applications of a Single‐Borehole Device for Measurements of Vertical Variations of Hydraulic Conductivity

Abstract

A dipole probe (DP) for measuring vertical variations of hydraulic conductivity has been designed, constructed, and tested in field conditions. The variable‐length device designed for the dipole flow test (DFT) consists of three packers separated by changeable spacer rods. The assembled DP is lowered into a well with a long screened interval. The packers are inflated, isolating two screened sections (chambers) between them. A small submersible pump, mounted on the central packer, transfers water from the upper (extraction) chamber into the lower (injection) chamber. This simultaneous injection and extraction creates a recirculatory flow within the aquifer. The chamber head responses are measured by two pressure transducers in the DP chambers. The DP can be used at discrete intervals along the entire well screen length. The DP has been successfully tested in a specially constructed well with a continuous screen in a highly conductive sand and gravel aquifer. During drilling, disturbed samples were collected using the split spoon method and the vertical profile of K was estimated from grain‐size analysis. A total of 153 DFTs were performed with various DP geometries. Results indicate that the chamber head changes are sensitive to aquifer properties, reach steady state rapidly, vary linearly with redrculation pumping rate, and can be controlled by changes in DP dimensions. Vertical profiles of K compare well with grain‐size analysis estimates.

Entrapped air effects on dipole flow test in sand tank experiments: Hydraulic conductivity and head distribution

“…Zlotnik and Ledder (1996) developed analytical solutions for estimating K in uniform anisotropic aquifers using the steady-state measurements of drawdown in dipole chambers. Zlotnik and Zurbuchen (1998) developed a dipole probe (DP) to conduct the DFT. The DP is a portable unit comprised of a submersible pump, three inflatable packers, and two transducers (Zlotnik and Zurbuchen, 1998, Figure 1).…”

“…The pump is operated at variable flow rates achieved by changing the pump frequency setting. The heads within the chambers are measured using a transducer mounted inside each chamber (Zlotnik and Zurbuchen, 1998). and Sutton et al (2000) expanded use of DFT by adding tracer for delineation of near-borehole annulus.…”

Source Zone Characterization Tool for Contaminated Groundwater Aquifers

“…This expression allows for the direct calculation of the path-lines in a dipole flow field (under the stated assumptions). Zlotnik and Zurbuchen [8] presented construction details of a dipole system and related components, and provided guidelines for the interpretation of pseudo steady-state field data to estimate hydraulic conductivity. Their interpretation method involves an assumption of steady-state flow and a prior knowledge of the aquifer isotropy ratio (a 2 = K r /K z ).…”

Vertical movement of water in a High Plains Aquifer induced by a pumping well

“…While results of the hydraulic properties for the shallow aquifer have been reported by Ayers et al (1998), Zlotnik and Zurbuchen (1998), Kilpatrick (1998), andChen et al (2003), data are particularly scarce for the aquitard and deep part of the HPA, i.e., the Ogallala Group, which is the major unit of the HPA. Butler and Tsou (2003) presented an analytical method to calculate leakage induced by a pumping well.…”