Modeling Hydraulic Conductivity of a Complex Confining Layer at Various Spatial Scales

The spatial variation of the hydraulic conductivity of a complex confining layer in the Netherlands is modeled at four different scales: the scale of sediment cores (10 −1 –10 0 m), the scale of the numerical model blocks (10 1 –10 2 m), the local scale (10 2 –10 3 m), and the regional scale (10 3 –10 5 m). Two stochastic methods are combined: (1) conditional (multiple indicator) simulation of texture classes to obtain three‐dimensional images of the lithology of the confining layer from borehole descriptions and (2) the statistical upscaling procedure of Indelman and Dagan [1993a, b] to derive the first‐ and second‐order statistics of hydraulic conductivities at the scale of the numerical model blocks. When the upscaling of the core‐scale conductivities is ignored, the local‐ and regional‐scale groundwater flow through the confining layer is predicted wrongly.