Measuring hydraulic conductivity with the borehole flowmeter

The variability of saturated hydraulic conductivity of the aquifer material is now recognized as a primary factor controlling the movement and spreading of solutes in ground water. The borehole flowmeter method discussed in this report is a promising field technique for measuring the vertical profile of horizontal hydraulic conductivity on a routine basis. By measuring profiles at different locations, a three-dimensional view of the hydraulic conductivity field is obtained. The flowmeter used in this study, which has a light-weight impeller (spinner) that rotates in responses to water moving vertically up or down the inside of the well, is calibrated in the laboratory to yield volumetric flow. For multiple flow states (i.e., before pumping the well and during pumping of the well, or during pumping at two different discharge rates) the flowmeter is used to obtain profiles of the discharge in the well along the entire screened length. From the vertical flow profiles, the mean radial flow to the well for each flow state is derived for each layer of a set of horizontal layers. This report contains detailed development of the theory, practical guidelines for flowmeter measurement, and a critical evaluation of the reliability and reproducibility of hydraulic conductivity data more » obtained with the borehole flowmeter method at the MADE site. Specific studies address the questions of the best method of well installation, the best method of well development, sensitivity of the method to parameter and measurement errors, and the adequacy of the assumptions in the theory. 47 refs. « less