Progress report on the ground-water, surface-water, and quality- of-water monitoring program, Black Mesa Area, northeastern Arizona — 1987-88

The Black Mesa, Arizona, monitoring program is designed to determine long-term effects on the water resources of the area resulting from withdrawals of groundwater from the N aquifer by the strip-mining operation of Peabody Coal Company. Withdrawals by Peabody Coal Company increased from 95 acre-ft in 1968 to 3 ,832 acre-ft in 1987. The N aquifer is an important source of water in the 5,400-sq-mi Black Mesa area on the Navajo and Hopi Indian Reservations. Water levels in the confined area of the aquifer declined as much as 95.1 ft near Keams Canyon from 1965 to 1988. Part of the decline in the measured municipal wells may be due to local pumping. During 1965-88, water levels in wells that tap the unconfined area of the aquifer have not declined significantly and have risen in many areas. Chemical analyses indicate no significant changes in the quality of water from wells that tap the N aquifer or from springs that discharge from several stratigraphic units, including the N aquifer, since pumping began at the mine.