Hydraulic head field estimation using kriging with an external drift: A way to consider conceptual model information

This study presents an approach to hydraulic head mapping based on kriging with an external drift in which the auxiliary variables are obtained by finite-element modeling. The approach relies on the idea that numerical solutions stemming from simple conceptual models are suitable candidates for the hydraulic head field drift. Indeed, these numerical head fields obey the groundwater flow equations and incorporate information gathered during site investigations such as parameter estimates, geology and boundary conditions. The approach is tested on 2D and 3D synthetic case studies, and is then applied to a real case involving the mapping of hydraulic heads within two large earth dams. In each case, the hydraulic head maps are compared quantitatively and qualitatively to those obtained by ordinary kriging and universal kriging with first order polynomials. It is shown that kriging with an external drift can improve both the precision and realism of the mapped head fields.