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Preliminary hydrogeologic assessment near Tassi and Pakoon Springs, western part of Grand Canyon-Parashant National Monument, Arizona

Scientific Investigations Report 2012-5276

Prepared in cooperation with the National Park Service
By:

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Abstract

Tassi and Pakoon Springs are both in the Grand Wash Trough in the western part of Grand Canyon-Parashant National Monument on the Arizona Strip. The monument is jointly managed by the National Park Service (NPS) and the Bureau of Land Management. This study was in response to NPS’s need to better understand the influence from regional increases in groundwater withdrawals near Grand Canyon-Parashant on the groundwater discharge from Tassi and Pakoon Springs. The climate of the Arizona Strip is generally semiarid to arid, and springs in the monument provide the water for the fragile ecosystems that are commonly separated by large areas of dry washes in canyons with pinyon and juniper. Available hydrogeologic data from previous investigations included water levels from the few existing wells, location information for springs, water chemistry from springs, and geologic maps. Available groundwater-elevation data from the wells and springs in the monument indicate that groundwater in the Grand Wash Trough is moving from north to south, discharging to springs and into the Colorado River. Groundwater may also be moving from east to west from Paleozoic rocks in the Grand Wash Cliffs into sedimentary deposits in the Grand Wash Trough. Finally, groundwater may be moving from the northwest in the Mesoproterozoic crystalline rocks of the Virgin Mountains into the northern part of the Grand Wash Trough. Water discharging from Tassi and Pakoon Springs has a major-ion chemistry similar to that of other springs in the western part of Grand Canyon-Parashant. Stable-isotopic signatures for oxygen-18 and hydrogen-2 are depleted in the water from both Tassi and Pakoon Springs in comparison to other springs on the Arizona Strip. Tassi Spring discharges from multiple seeps along the Wheeler Fault, and the depleted isotopic signatures suggest that water may be flowing from multiple places into Lake Mead and seems to have a higher elevation or an older climate source. Elevated water temperatures and a depleted stable-isotopic signature for Pakoon Springs suggest that the water may be traveling along a deep circulating flowpath, have multiple sources of water, been recharged at a high elevation, and (or) has an older climate source.

Geospatial Extents

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Preliminary hydrogeologic assessment near Tassi and Pakoon Springs, western part of Grand Canyon-Parashant National Monument, Arizona
Series title:
Scientific Investigations Report
Series number:
2012-5276
Year Published:
2013
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Arizona Water Science Center
Description:
iv, 12 p.
First page:
i
Last page:
12
Country:
United States
State:
Arizona
Other Geospatial:
Grand Canyon-parashant National Monument;Tassi Spring;Pakoon Spring
Online Only (Y/N):
Y
Additional Online Files(Y/N):
N