Within the past five years all the groups of continuously flowing chloride springs in Whakarewarewa have had some interruption to, or cessation of, flow. This indicates that the geothermal field is in decline. An historical survey establishes that formerly the response time of the spring to minima in cumulative deviation of rainfall was about 8 years consistent with an analogue model of the field. The recent response time, less than one year, is consistent with the model only when the effects of exploitation are included, indicating that withdrawal from wells is causing a major decline in the field.