Geohydrology and effects of water use in the Black Mesa area, Navajo and Hopi Indian Reservations, Arizona

Geochemical analyses of ground-water ages, recharge rates, and hydraulic conductivity of the N aquifer, Black Mesa area, Arizona

“…These models assumed annual recharge to the system in the Shonto area to be about 4,800 acre-ft and that leakage from the D aquifer into the N aquifer was estimated to be 200 acre-ft annually. The potentiometric surface of the D aquifer in 1964, however, was as much as 600 ft higher than the surface of the N aquifer (Eychaner, 1983); therefore, it is possible that leakage from the D aquifer accounts for a larger percentage of water in the N aquifer. The Carmel Formation is known to yield water to springs and generally is between 150 and 250 ft thick in the study area.…”

“…An earlier study of the aquifer by Eychaner (1983) noted a small amount of leakage from the D aquifer into the N aquifer and that an increase in leakage should appear as an increase in dissolved-solids concentrations in wells in the N aquifer. Major-ion chemistry data obtained in this study made possible an examination of the extent of leakage between the D and N aquifers.…”

“…Water levels (Eychaner, 1983) indicate that the potentiometric surface is highest near Shonto and lowest along Moenkopi Wash and near Laguna Creek. Ground water would thus flow from the Shonto area generally in a southward direction under Black Mesa.…”

“…Water levels indicate that precipitation recharges the N aquifer primarily in the Shonto area where the Navajo Sandstone is exposed. Recharge has been assumed to be about 3 percent of the precipitation in the outcrop area near Shonto and about 1 percent in other outcrop areas (Eychaner, 1983). A numerical model of the Black Mesa ground-water system was developed by Eychaner (1983) to improve the understanding of the N aquifer and to compare possible effects of alternative pumping scenarios.…”

“…Recharge has been assumed to be about 3 percent of the precipitation in the outcrop area near Shonto and about 1 percent in other outcrop areas (Eychaner, 1983). A numerical model of the Black Mesa ground-water system was developed by Eychaner (1983) to improve the understanding of the N aquifer and to compare possible effects of alternative pumping scenarios. Improved methods in simulating ground-water systems and additional data on the N aquifer were used by Brown and Eychaner (1988) to update the numerical model.…”