Land-subsidence and ground-water storage monitoring in the Tucson Active Management Area, Arizona

Fact Sheet 084-00
Prepared in cooperation with the Arizona Department of Water Resources, City of Tucson, Pima County, and National Oceanic and Atmospheric Administration National Geodetic Survey
By: , and 



The Tucson Active Management Area (TAMA) comprises two basins--Tucson Basin and Avra Valley. The TAMA has been directed by Arizona ground-water law to attain an annual balance between groundwater withdrawals and recharge by the year 2025. This balance is defined by the statute as "safe yield." Current ground-water withdrawals exceed recharge, resulting in conditions of ground-water overdraft, which causes removal of water from ground-water storage and subsidence of the land surface. Depletion of storage and associated land subsidence will not be halted until all discharge from the system, both natural and human induced, is balanced by recharge.

The amount of the ground-water overdraft has been difficult to estimate until recently because it could not be directly measured. Overdraft has been estimated using indirect water-budget methods that rely on uncertain estimates of recharge. As a result, the status of the ground-water budget could not be known with great certainty.

Gravity methods offer a means to directly measure ground-water overdraft through measurement of changes in the gravitational field of the Earth that are caused by changes in the amount of water stored in the subsurface. Changes in vertical position also affect the measured gravity value and thus subsidence also must be monitored. The combination of periodic observations of gravity and vertical positions provide direct measures of changes in stored ground water and land subsidence.

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Land-subsidence and ground-water storage monitoring in the Tucson Active Management Area, Arizona
Series title Fact Sheet
Series number 084-00
DOI 10.3133/fs08400
Year Published 2000
Language English
Publisher U.S. Geological Survey
Contributing office(s) Arizona Water Science Center
Description 4 p.
Country United States
State Arizona
Other Geospatial Avra Valley;Tucson Basin
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