Improvement of in situ hydraulic conductivity tests for riverbeds under the influence of infiltration intake: A case study of the Oława River, SW Poland.

The vertical hydraulic conductivity (K) of riverbeds plays a pivotal role in controlling water exchanges between the surface water and groundwater. The recent papers have focused on the spatial and temporal variability of K (K measured in the "z" direction), while point measurement schemes seem to require more attention. The most popular measurement technique is the falling head method, in which a PVC pipe is placed in the riverbed. The most commonly used formulas to determine hydraulic conductivity are those based on the Darcy's law and its modifications. This article presents how the falling head method should be carried out and what errors need to be considered in conditions of the riverbank intake. The simultaneous measurements and analyses of the falling head vs. the riverbed head can produce satisfying outcomes and reduce errors. A full utility MS Excel spreadsheet based on an automated formula with a solver was developed.