A Review of the Hydrogeology of the Tauhara Domestic Bores, Taup?, New Zealand

Abstract

Five hundred and twenty-four domestic bores have been installed for water and space heating in Taup? township, mainly within the resistivity boundary of the Tauhara geothermal field. Geochemistry data indicate that the dominant water type extracted from the allocated aquifer is steam-heated waters. Due to minimal data existing on the lithological conditions of the bores, lithostratigraphic data from well THM-18 is used for interpreting the subsurface stratigraphy of the allocated aquifer area. No significant variations in temperature-elevation relationship are observed at different geographical areas across Taup? township. Elevation and bore depth measurements suggest that the Oruanui Formation is the most common lithological unit from which hot fluids are extracted. The Upper Huka Falls Formation is intersected by fewer bores and records lower temperatures than the overlying Oruanui Formation. Fluids exceeding 160 °C were encountered in the Middle Huka Falls Formation, however the formation is a less practical drilling target than the Oruanui Formation aquifer for future domestic bore drilling due to its situation at significantly greater depths. The Oruanui Formation is the most productive and most ideal target zone for future fluid extractions due having a reliable high temperature resource at a relatively shallow depth. Future monitoring of the bores could create a better understanding of the relationship between the domestic bores and surface geothermal features and streams, which have seen a general decline in discharge in recent years.