ABSTRACT
The piezometric surface of the uppermost aquifers in the Wairakei–Tauhara area shows a gradient towards the Waikato River and Lake Taupo. This implies that rainfall is recharging these aquifers from surrounding ground at higher elevation and that groundwater flow follows the gradient towards eventual discharge into surface water bodies. Hydrological effects are also observed from processes such as: subsurface boiling during pressure drawdown, upflows of steam into parts of the shallow aquifers, and downflows of liquid into steam zones. In addition, geological influences that are significant include isolation and perched separation of aquifers due to hydrothermal clay alteration, and partial separation of aquifers by impermeable mudstone aquicludes.
