| Abstract |
A significant decline in groundwater level at Wairakei has apparently only occurred between the production borefield and Geyser Val ley, and within the Karapiti thermal area. Over most of the production borefield, groundwater temperature is now at boiling point for depth, and the top of the steam zone which underlies the groundwater, is now near the top of the Huka mudstone. Consideration of recent gravity increases in the production borefield and decreasing steam zone pressure, suggests the permeability contrast at the top of the mudstone is now a controlling factor on the depth extent of the steam zone. The only clear evidence of cold groundwater movement towards the borefield is to be found on the northeast boundary, near the region of intense subsidence. |