Commercial-scale development of western oil shale resources will require a supply of water for both extraction and reclamation purposes. This paper summarizes some of the information on the occurrence of potential local supplies of water in the Piceance Creek Basin-Uinta Basin areas of northwest Colorado and northeast Utah. The discussion is somewhat hypothetical in that it is restricted to the physical occurrence of water with emphasis on water resources in each basin. Of course, the many potential constraints on water use (including economics, water quality, legal and other institutional factors) are necessarily secondary to the ultimate constraint, its physical occurrence. Perhaps the most obvious constraint is that of water rights and water laws. For example, "mining" of some of the ground water is herein assumed to be necessary for technically sound management and utilization of the water resource, but the hydrologic effects of such "mining" would require accommodation under water laws and agreements.