A DISCUSSION OF SCALE EFFECTS ON HYDRAULIC CONDUCTIVITY AT A GRANITICSITE (EL BERROCAL, SPAIN)

Scale effects on hydraulic conductivity (i.e. increase in the value of K with increasing scale of measurement) have been reported in the lit erature. Here, we summarize extensive tests performed at El Berrocal, a granitic site in Central Spain, to study whether such effects indeed appear. In fact, median hydraulic conductivities clearly increase wit h measurement scale. We argue, however, that large scale measurements may be biased towards high K values because they are performed in the most permeable zones, where pumping rates can be high. This is support ed by the fact that cross-hole transmissivities and hydraulic conducti vities consistently fall below the corresponding values at the pumping interval.