The Canyon Diablo area includes about 1,400 square miles in northeastern Arizona. The main source of ground water is the Coconino aquifer, which includes the Kaibab Limestone, the Cononino Sandstone, and the upper member of the Supai Formation. In places the alluvium and volcanic rocks yield water to wells and springs. Information on the map includes altitude of the water level, depth to water, and specific conductance and fluoride concentration in the water. Scale 1:125,000. (USGS)