No abstract

In the absence of well-documented pumping tests, we investigate whether a reliable estimate of transmissivity T can be obtained using historical records of specific capacity data in granular and fractured-rock aquifers. Transmissivity values are calculated from the specific capacity data Q/s in several hundred wells located in the Saguenay-Lac-Saint-Jean region (Canada), with an iterative method applied to the Cooper-Jacob equation. The results are compared with short-and longduration pumping tests performed throughout the region. We demonstrate that values of transmissivity compare well between the different types of tests for each lithology, when the scale of the test is similar. Therefore, using historical information easily increases the number of transmissivity values that can be estimated over a region. These values can be integrated in regional numerical models. Moreover, this study shows that T = 4.48(Q/s) 1.15 with R 2 = 0.66 for granular aquifers. This new empirical relationship can be used in similar environments.

An improperly sealed casing can produce a direct hydraulic connection between two or more originally isolated aquifers with important consequences regarding groundwater quantity and quality. A recent study by Richard et al. (2014) investigated a monitoring well installed in a fractured rock aquifer with a defective casing seal at the soil-bedrock interface. A hydraulic short circuit was detected that produced some leakage between the rock and the overlying deposits. A falling-head permeability test performed in this well showed that the usual method of data interpretation is not valid in this particular case due to the presence of a piezometric error. This error is the direct result of the preferential flow originating from the hydraulic short circuit and the subsequent re-equilibration of the piezometric levels of both aquifers in the vicinity of the inlet and the outlet of the defective seal. Numerical simulations of groundwater circulation around the well support the observed impact of the hydraulic short circuit on the results of the falling-head permeability test. These observations demonstrate that a properly designed falling-head permeability test may be useful in the detection of defective casing seals.