EFFECT OF CONDITIONING RANDOMLY HETEROGENEOUS TRANSMISSIVITY ON TEMPORAL HYDRAULIC-HEAD MEASUREMENTS IN TRANSIENT 2-DIMENSIONAL AQUIFER FLOW

We investigated the effect of conditioning transient, two-dimensional groundwater flow simulations, where the transmissivity was a spatial r andom field, on time dependent head data. The random fields, represent ing perturbations in log transmissivity, were generated using a known covariance function and then conditioned to match head data by iterati vely cokriging and solving the flow model numerically. A new approxima tion to the cross-covariance of log transmissivity perturbations with time dependent head data and head data at different times, that greatl y increased the computational efficiency, was introduced. The most not iceable effect of head data on the estimation of head and log transmis sivity perturbations occurred from conditioning only on spatially dist ributed head measurements during steady flow. The additional improveme nt in the estimation of the log transmissivity and head perturbations obtained by conditioning on time dependent head data was fairly small. On the other hand, conditioning on temporal head data had a significa nt effect on particle tracks and reduced the lateral spreading around the center of the paths.