Book excerpt: "This project was initiated in July 1976, to determine what effects the surface mining of coal would have on the regional shallow groundwater systems in a semiarid western region. The Powder River Structural Basin of Montana and Wyoming was chosen as the study area for the project since it typifies the western semiarid climate, and large scale surface coal mining operations are present in the area. Also, these mining operations are expected to increase dramatically in the future in Powder River Basin"--Page I-1.