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Simulation of five ground-water withdrawal projections for the Black Mesa area, Navajo and Hopi Indian Reservations, Arizona

Water-Resources Investigations Report 88-4000

By:
and

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Abstract

The N Aquifer is the main source of water in the 5,400 sq mi Black Mesa area in the Navajo and Hopi Indian Reservations in northeastern Arizona. Water in the aquifer is under confined conditions in the central 3,300 sq mi of the area. Maximum saturated thickness is about 1,050 ft. Annual groundwater withdrawals from 1972 through 1986 averaged 5,480 acre-ft and included 3,820 acre-ft used to operate a coal mine on Black Mesa. As a result, water levels have declined in a large part of the aquifer. The coal company has applied for a permanent permit under the Surface Mining Control and Reclamation Act of 1977. An existing mathematical model of the aquifer in the Black Mesa area was converted to a newer model program and recalibrated by using revised estimates of selected aquifer parameters and a finer spatial grid. The model was used to simulate four groundwater withdrawal alternatives that combined the existing and proposed mining plans with projected constant or increasing pumpage for nearby communities. A fifth alternative combined increasing community pumpage with no mine withdrawals and was used as a basis for comparison. Simulated water levels for the year 2031 in the coal-lease area are projected to be 60 ft lower than in 1985 for the proposed mining plan combined with growing community pumpage and > 100 ft lower than predevelopment water levels over an area of 1,660 sq mi. Groundwater would rise to within 100 ft of predevelopment levels < 10 yr after mine withdrawals cease. Withdrawals at the mine were a minor factor in determining simulated water levels at most communities in the study area. Water levels at Tuba City were not affected by mine pumpage in any projection. (Author 's abstract)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Simulation of five ground-water withdrawal projections for the Black Mesa area, Navajo and Hopi Indian Reservations, Arizona
Series title:
Water-Resources Investigations Report
Series number:
88-4000
Edition:
-
Year Published:
1988
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
v, 51 p. :ill., maps ;28 cm.