Literature concerning pressure waves in porous media is reviewed, and an example in the Snake River Plain is discussed. Two types of literature were required, one dealing with the groundwater hydrology of the Snake River Plain and the other with the theoretical aspects of pressure wave movement in aquifers. The first report of a pressure wave phenomenon in the Snake River Plain appeared in 1965. The phenomenon was brought about by extremely high flows in the Big Lost River during the summer of 1965. By December, 1965, the water table had risen more than 2 ft over a 400 sq mi area, and over part of this area had risen as much as 6 ft. The fact that the water table rose was not unexpected, but the rate at which it rose in areas considerably removed from the recharge area was unexpected. There is not enough information as yet to explain the phenomenon, and several statements have been made emphasizing the need for additional research. (Author)