COKRIGED ESTIMATION OF AQUIFER TRANSMISSIVITY AS AN INDIRECT SOLUTION OF THE INVERSE PROBLEM - A PRACTICAL APPROACH

A simple approach to indirectly address the inverse problem in steady state for aquifer transmissivity has been studied. The data on transmissivity and water level have simultaneously been used to produce the spatial distribution of transmissivity through cokriging. A simple relation between transmissivity and head was used to calculate coherent head covariance and head-transmissivity cross-covariance based on a chosen transmissivity covariance. Two theoretical aquifer models were studied: one with simple and almost parallel flow and the other with a complex flow and source terms. The results were compared with the theoretical values. The comparison shows that a better estimation both in terms of the estimated values of transmissivities and in terms of the standard deviation of the estimation errors is obtained when water levels combined with transmissivity are used than in case of the estimation with transmissivity alone, provided the groundwater flow direction in a close neighborhood of the estimation point is carefully calculated.