Fig. 5. Example of electrokinetic electric potential difference for a decreasing water table and deionized water. (a) Evolution of the upstream and downstream water levels. The upstream level was maintained at 20 cm; the downstream started at 20 cm (i.e., no flow) and was decreased by 3-cm steps until 5 cm. (b) Corresponding electric potential difference between the electrode located at (x,y,z) = (–6, 12, 5 cm) and the reference electrode located in the upstream reservoir (see Fig. 3).