The Impeller Meter for measuring aquifer permeability variations: Evaluation and comparison with other tests

Abstract

A knowledge of the variation of horizontal hydraulic conductivity with vertical position, K(z), is important in understanding the transport and dispersive properties of aquifers. Using an impeller meter to measure the discharge distribution in a screened well while pumping at a constant rate is a promising technique for obtaining the K(z) function. Such an application is described herein, and the resulting K(z) functions are compared with those obtained previously using tracer tests and multilevel slug tests. Impeller meter data were the most convenient to obtain, and tracer data the most difficult. The K(z) functions obtained by the three methods were not identical but quite similar overall. This similarity between both borehole tests and the larger-scale tracer test showed that nonstationary hydraulic conductivity trends, in a stochastic hydrologic sense, exist in the test aquifer. The impeller meter method was better able to detect the higher K layers than was the multilevel slug approach. Overall, the results suggest that a practical strategy for "fitting" impeller meter, tracer, or multilevel slug test data to a given aquifer is to use the selected testing procedure to obtain a dimensionless K/• distribution and then a standard pumping test to measure •. Combining both types of information enables dimensional values for K(z) to be calculated. In low permeability aquifers or near the bottom of a test well the fluid velocity due to pumping may be below the stall velocity of an impeller. Thus there is a definite need for the commercial development of more sensitive flow-measuring devices such as heat pulse flowmeters (Hess, 1986), which will extend the resolution of this field method. 1677

Investigation of Hexavalent Chromium Flux to Groundwater at the 100-C-7:1 Excavation Site

“…Ambient flow survey profile information is used to correct dynamic flow meter survey results for background vertical-gradient conditions. The analytical method used for calculating the vertical distribution of relative hydraulic conductivity from dynamic EBF surveys is summarized in Molz et al (1989) and Boman et al (1997). Briefly stated, assuming that a constant pumping rate and pseudo-steady-state conditions are reached during pumping, the normalized relative hydraulic conductivity for the i th layer within the aquifer can be calculated per Equation (1).…”

Developing conceptual hydrogeological model for Potsdam sandstones in southwestern Quebec, Canada

“…After ambient flow had been measured, a pump was lowered into each well with the borehole flowmeter suspended below it and the vertical distribution of transmissivity was determined by the flowmeter/pumping technique (Morin et al 1988;Molz et al 1989). In this method, the pumping rate at the surface is maintained constant, drawdown is monitored, and vertical flow in the borehole is measured with respect to depth by raising and lowering the flowmeter.…”

Hydrogeologic characterization of six sites in southeastern Minnesota using borehole flowmeters and other geophysical logs

“…In addition, there will be two other data points: the drawdown between ambient and pumping conditions, and the pumping rate. Thus, a combination of flow profiles under ambient and steady pumping conditions provide the 2N data points needed to "solve" for the 2N values of T and H. The general numerical formulation of the flow equations used to solve the flow equations for the T and H values are given by Molz et al (1989) and Paillet (1998).…”

“…In such situations, the relative proportion of inflow in a given waterproducing interval may be very different from the relative transmissivity of that interval. The relative amount of inflow to the borehole, calculated from the difference in rate of flow above and below and inflow interval, is used to estimate inflow zone transmissivity (Molz et al, 1989). The inflow under quasi-steady conditions is proportional to the product of transmissivity and hydraulic-head difference driving the flow.…”