SPATIAL VARIABILITY OF HYDRAULIC CONDUCTIVITY OF AN UNCONFINED SANDY AQUIFER DETERMINED BY A MINI SLUG TEST

The spatial variability of the hydraulic conductivity in a sandy aquifer has been determined by a mini slug test method. The hydraulic conductivity (K) of the aquifer has a geometric mean of 5.05 x 10(-4) m s-1, and an overall variance of In K equal to 0.37 which corresponds quite well to the results obtained by two large scale tracer experiments performed in the aquifer. A geological model of the aquifer based on 31 sediment cores, proposed three hydrogeological layers in the aquifer concurrent with the vertical variations observed with respect to hydraulic conductivity. The horizontal correlation length of the hydraulic conductivity has been determined for each of the three hydrogeological layers and is found to be small (1-2.5 m). The asymptotic longitudinal dispersivity of the aquifer has been estimated from the variance in hydraulic conductivity and the horizontal correlation length, to be in the range of 0.3-0.5 m compared with a value of 0.42 m obtained in one of the tracer tests performed.