The groundwater protection program characterizes groundwater quality in each of Arizona’s 51 basins. Following a sample plan approval, comprehensive sampling is conducted to determine groundwater quality, including random sampling, systematic grid-based random sampling, stratified random sampling and, occasionally, higher density sampling around targeted land uses.
Importance of Groundwater Testing
An estimated 300,000 or more Arizonans get their drinking water from private wells – wells not subject to public water system regulations. ADEQ basin studies provide important information about expected basin groundwater quality and any changes over time, as well as where specific groundwater quality problems may occur. These studies are a valuable resource for private well users in meeting water quality standards set by the federal Safe Drinking Water Act (SDWA).
Testing Groundwater Quality
ADEQ collects samples for SDWA inorganic analysis as well as oxygen and hydrogen isotopes at each site. Radiochemistry and radon analysis also are frequently conducted, while Volatile Organic Compounds (VOCs) — currently-registered pesticides, banned pesticides, perchlorate and other types of samples — are sometimes collected where they likely are to be encountered. Groundwater samples collected for regional studies are analyzed to determine significant differences in parameter levels between indices, such as sub-basins, physiographic areas and aquifers. Similar analyses are conducted on data collected from index wells or from historical groundwater studies to determine if any significant changes have occurred over time.
Reporting Groundwater Data
Data collected by this program is incorporated into ADEQ's Groundwater Database and provided to the well owner. This database includes all samples collected by the ADEQ Ambient Groundwater Monitoring Program as well as other ADEQ monitoring programs.
ADEQ also publishes a comprehensive Open File Report and a condensed four-page Fact Sheet for each basin. The Open File Report provides an in-depth hydrologic analysis of the basin, and the Fact Sheet, a brief overview of basin groundwater quality. ADEQ selects index wells in each basin to resample in the future to track and determine groundwater quality trends and changes over time.
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