A Simple Method to Apply Measured Flux and Head Data for the Estimation of Regional Hydraulic Conductivities

Abstract

Modeling of groundwater flow through basins has to be based on regional-scale hydraulic conductivities. We show how regional conductivities can simply be calibrated using direct and indirect measurements of hydraulic heads and fluxes. Groundwater models are conventionally based on recharge flux specified on the model’s top boundary. In the 1960s Toth presented a model of regional groundwater flow based on head specified on the top boundary. This approach resulted in the discovery of local, intermediate and regional flow systems. On the other hand, a top head condition may lead to unrealistic recharge rates. Combining the advantages of both flux and head boundary conditions, we analyze groundwater flow using two models: a flux model and a head model. The difference between the two solutions shows the regions where measured heads and fluxes can calibrate the initial hydraulic conductivity, as well as the regions where measured heads and fluxes cannot. Using Darcy’s law to the differences results in calibration. This so-called Double Constraint Method can be made more reliable by repeated calibrations under different hydrological conditions. A Kalman Filter then determines an uncertainty that is appreciably smaller than the observation error.