Reservoir depletion at the Geysers from 1974 to 1977 is evident in measured changes in gravity, surface strain, and pore pressure drainage The drainage area increased about 20%, the maximum gravity decrease was about ~120 μGal, and the maximum elevation change was about 6 cm during this period. Since the net mass withdrawl is known, it may be combined with the gravity change to estimate a drainage volume. The maximum drainage volume is 25 km3. Because the depth of the caprock and extent of the pore pressure drainage is known, this volume limit implies that no significant mass withdrawal occurs below a depth of 4 km. The ratios of surface elevation changes to horizontal contraction coinciding with the drainage area imply an equant drainage geometry, assuming that fluid production produces negative dilatation. Using the same cylindrical geometry used to model the gravity, negative dilational strain rates of 4 to 5¿10-5/yr were found to produce the observed surface displacements. The likelihood of boiling in the system to produce steam combined with apparent large bulk moduli (from seismic velocities) and small poor pressure declines suggest that most of the reservoir contraction is due to cooling.