The Recharge to the Wairakei Reservoir

Abstract

A heat balance on the changes at Wairakei due to exploitation gives a rough estimate of the enthalpy of the recharge entering the productive reservoir as 1000 As this fluid will have already gained some heat by passage through peripheral rocks, i t is indicated that some of the recharge induced by exploitation is of surface groundwater. Temperatures in the steam zone and in liquid beneath it, and the pattern of upflow and downflow in wells, indicate that recharge of deep hot water continues to occur in the northwestern (Te Mihi) sector of the field, and flowsdue west into the Colder water is invading the western borefield along the Kaiapo and Wairakei Faults. Ultimately production will decline and fail in the present borefield, as cold water enters more pervasively. A productive resource will at Mihi which could be used to feed either the present station o r a new plant at Te Mihi. as well as the present pattern of withdrawal. I n particular there should be no reinjection at Te Mihi, or 221. Reinjection plans Should reflect the future