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Simulation analysis of water-level changes in the Navajo sandstone due to changes in the altitude of Lake Powell near Wahweap Bay, Utah and Arizona

Water-Resources Investigations Report 85-4207

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Abstract

A two-dimensional, finite difference, digital computer model was used to simulate various concepts of groundwater flow near Wahweap Bay, Lake Powell. The filling of Lake Powell started in March 1963; and by 1983 the lake had risen almost 550 ft. This resulted in a maximum observed water level rise of 395 ft in a well in the Navajo Sandstone 1 mi from the lake. A steady-state model was prepared with subsurface recharge rates of 5,720 acre-ft/yr, 10,440 acre-ft/yr, and 14,820 acre-ft/yr, resulting in a range of hydraulic conductivity of 0.25 to 3.38 ft/da. Comparing measured and simulated water level changes resulted in a range of specific yield of 0.02 to 0.15. Using larger values for hydraulic conductivity in the model area corresponding to the axis of the Wahweap syncline and the Echo monocline was instrumental in attaining a reasonable match for the water level distribution. This supports previous concepts that areas where rocks are structurally deformed more readily transmit groundwater because of the higher degree of fracturing. Using the most likely simulation of the flow system, groundwater storage in the Navajo increased by about 25,000 acre ft/mi of shoreline form 1963-83, but the flow system will require about 400 yr to reach a state of equilibrium. (Author 's abstract)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Simulation analysis of water-level changes in the Navajo sandstone due to changes in the altitude of Lake Powell near Wahweap Bay, Utah and Arizona
Series title:
Water-Resources Investigations Report
Series number:
85-4207
Edition:
-
Year Published:
1986
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
v, 45 p. :ill., maps ;28 cm.