A previous empirical analysis of rainfall to January 1983 at Rotorua led to a deduction that periods of low rainfall preceded temporary cessations of geothermal springs in 1924 and 1943 by about 8 years. That analysis is shown here to approximate flow from a spring fed by a leaky reservoir. Upon adding recent rainfall an additional minimum of pressure in such a reservoir is seen to have occurred in 1983--85. With the deduced 8-year response, a natural decline in the srping flow would thus be expected in 1991--93. Using this spring-reservoir model, minima of flow are indeed apparent in 1924 and 1943, and there is a downward trend to the present. ¿ 1987 American Geophysical Union