Large low-grade ore bodies have been discovered in Copper Basin, and a large copper-mining operation is anticipated in the near future. Hydrologic data are being collected to provide the data base necessary to determine the effects of a potential mining operation on the water resources of the area. The area of potential depletion or contamination of water supplies is the 50-square-mile alluvial slope downgradient from Copper Basin. In the Copper Basin area the streams generally are dry, except for the perennial flow in a 3-mile-long reach of Kirkland Creek, where the base flow ranges from about 1 to 3 cubic feet per second.
The water in the alluvium, which is more than 1,000 feet thick in places, generally is under unconfined conditions. The direction of ground-water movement is generally southwesterly toward Skull Valley Wash and Kirkland Creek. The depth to water in wells ranges from less than 10 to 675 feet below the land surface. Near the center of the area, test wells penetrate a clay confining bed at the base of the alluvium and an underlying sequence of volcanic rocks, which is more than 1,000 feet thick and contains water under confined conditions.
Pump tests indicate that the confining bed forms a barrier between the water in the alluvium and the water in the volcanic rocks and that, initially, pumping from the volcanic rocks would not affect the water level in the alluvium. The areal extent of the volcanic sequence is not known.
