In the recharge area, oxidising conditions occur and dissolution of calcium and bicarbonate dominates. As the water continues to move down dip, further modifications are at first limited. By observing the redox potential (Eh) of abstracted groundwater, a sharp redox barrier was detected beyond the edge of the confining layer, corresponding to the complete exhaustion of dissolved oxygen. Bicarbonate increases and the pH rises until buffering occurs at about . Sulphate concentrations remain stable in the oxidising water, but decrease suddenly just beyond the redox boundary due to sulphate reduction. Groundwater becomes steadily more reducing down dip, as.
