Comparison of the results of pumping and tracer tests in a karst terrain

Abstract

Pumping and tracer tests are commonly used to measure aquifer parameters such as hydraulic conductivity. Hydraulic conductivity is, however, difficult to characterize; especially in heterogeneous karst terrain. In this research, results of pumping and tracer tests are combined to determine hydraulic conductivities of the karst terrain at the Salman Farsi Dam Site. Pumping test data were analyzed by dual-porosity analytical models. The tracer tests were used to determine seepage velocities based on the assumption of Darcy's law, with calculated Reynolds numbers consistent with laminar flow. Geometric means of the hydraulic conductivities calculated from tracer tests were consistently higher than results derived from pumping tests. Movement of injected dye in a natural groundwater flow system is strongly controlled by preferential flow paths; therefore the estimated hydraulic conductivity is mainly affected by major dissolution openings. However, estimated hydraulic conductivity based on the pumping-test data is representative of the average hydraulic conductivity. In addition, Lugeon (or packer) tests were used to delineate the distribution of hydraulic conductivity within three boreholes.

Estimation of hdraulic conductivity using geoelectrical data for assessing of scale effect in a karst aquifer

“…Hydraulic conductivity has also been calculated for different scales and methods at the SFDS (Tab. 3) by Nassimi and Mohammadi (2016). Tab.…”

“…5); be-cause the distance in the samples studied to obtain the Thompson equation (maximum 0.02 m) is much less than the geometric mean of the distance in the Lugeon (30 m), pumping (97.8 m) and tracer tests (249.3 m). In other words, in the karst terrain, estimated values of K based on larger scale experiments is bigger (Bear 1972;Rovey & Cherkauer 1995;Vacher & Florea 2015) and more reliable (Vandenbohede & Lebbe 2003;Nassimi & Mohammadi 2016) than those based on the smaller scale, due to important role of preferential flow paths in the larger scale. Rovey and Cherkauer (1995) showed hydraulic conductivity increases approximately linearly with distance on log-log plots for a range between 20 and 220 m. Some research also showed scale effect in the karst aquifers (Király 1975;quinlan et al 1992;Rovey 1994;Sauter 2005).…”

“…In pumping test with boreholes scale, hydraulic conductivity is affected by both the matrix and fractures (Moench 1984;Nassimi & Mohammadi 2016), but with increasing the scale of the experiments the role of fractures and dissolution routes are increased, and with decreasing the scale the role of matrix are increased. Therefore it is expected that the hydraulic conductivity increases with increasing the scale, and the hydraulic conductivity decreases with decreasing the scale.…”

“…ESTIMATION OF HyDRAULIC CONDUCTIVITy USING GEOELECTRICAL DATA FOR ASSESSING OF SCALE EFFECT IN ...Tab. 3: Estimation of hydraulic conductivity via tracer, pumping and Lugeon tests at the SFdS (extracted fromNassimi & Mohammadi 2016). QR means borehole.…”

Utilization Plan of Underground River in Dry Area

“…Pumping test on hydrogeological research is conducted to analyze the potency of groundwater as raw water source [18].…”