Maps showing ground-water conditions in the lower San Pedro Basin area, Pinal, Cochise, Pima, and Graham Counties, Arizona—1979

The lower San Pedro basin area includes about 1,550 square miles in southeastern Arizona. The area depends almost entirely on groundwater for its water supplies. In 1978 the estimated groundwater pumpage was 55,000 acre-feet, 30,000 acre-feet of which was used for irrigation. Withdrawal of groundwater has had little effect on groundwater levels in the area. Information shown on the maps includes depth to water, altitude of the water level, spring discharge, chemical quality of the groundwater, and irrigated area. Hydrographs of the water level in selected wells and a table of historical pumpage also are included. Scale 1:125,000. (USGS)