Radioisotope Tracing of Water Movement at Wairakei

Abstract

One of the key features of a geothermal field is the movement of water in the near surface region. In an undisturbed field there will be an upflow associated with the areas of highest temperatures (water movement being the dominant heat transfer mechanism), as well as cross-flows associated with lateral pressure variations and the usually heterogeneous structure. An exploited field can be expected to show more local pressure variations and therefore more of the cross-flow type. O f particular concern in exploited fields are the possibilities of near surface recharge and short circuitry flows from cooler parts of the field the production zones.