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Cienega Creek and Davidson Canyon

PAG’s hydrologic monitoring and research projects have been a significant part of the Watershed Planning Program since the mid 1980s when research began on Cienega Creek. Since that time, we have conducted a variety of projects within the Cienega Creek drainage, as well as nearby surface water systems.

In 2007, PAG received a grant from the Arizona Department of Water Resources, under its Arizona Water Protection Fund program. This two-year project consists of habitat surveys, and groundwater and streamflow monitoring near a large erosional headcut feature that appeared on the creek in 2001.


CAP recharge/groundwater mixing studies

Since 1997, PAG has evaluated stable isotope data for water withdrawn from the City of Tucson’s storage and recovery projects located in Avra Valley. The Pima Mine Road Recharge Project was added to the program in 2009.  These facilities are used to recharge Central Arizona Project (CAP) water, which is delivered to Tucson from the Colorado River. The purpose is to use the stable isotope composition of the pumped water to determine the proportion of CAP water vs. groundwater in the subsurface aquifer. As recharge continues over time, there is a higher percentage of CAP water mixed with the aquifer’s groundwater.

In 2008, PAG stopped working on the Central Avra Valley Storage and Recovery Project (CAVSARP) to make room for collection of Southern Avra Valley Storage and Recovery Project (SAVSARP) samples.  Isotope sampling at the CAVSARP site was restarted in 2010.

PAG is currently evaluating isotope data from CAVSARP, SAVSARP and Pima Mine Road.

Well studies in shallow groundwater area

PAG released the updated and expanded report, Shallow Groundwater Areas in Eastern Pima County, Water Well Inventory and Pumping Trend Analysis, in 2012.  As our region’s population expands and groundwater aquifers become developed, it becomes increasingly important to understand pumping trends for sensitive areas, such as shallow groundwater areas, so that riparian habitats and private well owners are not compromised.

Shallow groundwater areas have water tables that lie less than 50 feet below ground surface, and they are often demarcated by indicator vegetation, such as mesquite and cottonwood trees.   The study identifies 32 shallow groundwater areas, grouped into 10 regions and uses ADWR and PAG well data to describe water level changes, water use trends, well densities and drilling histories.   The report includes a series of trend analyses on pumping data from non-exempt wells, but it also provides a general summary of data collected from the exempt wells*. The trend analysis helps identify those areas that have experienced increased or decreased groundwater withdrawals from non-exempt wells over the last two decades.
*Exempt wells are permitted to withdraw up to 35 gallons per minute (gpm), but no pumping data is available for these wells. Non-exempt wells, may pump more than 35gpm and are required to report pumping volumes to the state.

Because riparian trees depend on groundwater, they become vulnerable if groundwater levels decline. While habitat supported in shallow groundwater areas is critical to the region's wildlife, the water resources in these basins also provide water to numerous private well owners and public water systems.  With continued warming and drought, there will undoubtedly be increased competition for water resources in these delicately balanced systems. Monitoring water levels and improving education to private well owners are two important future steps to ensure that riparian areas associated with shallow groundwater areas are not adversely impacted in the future. 

CAGRD Report & Map

In September 2011, Pima Association of Governments released the "Central Arizona Groundwater Replenishment District Membership in the Tucson Active Management Area" report. The report contains data current to 2009. The purpose of the report is to provide regional managers and the public with updated information on Central Arizona Groundwater Replenishment District (CAGRD) membership in the context of its impact on Assured Water Supply (AWS).

Analysis includes calculations of obligated replenishment for members, membership growth trends and location of recharge facilities. The Central Arizona Project (CAP) also has used this report to address boundary reconciliation issues. Several concerns arise when considering the widespread dependence on the GRD to meet AWS requirements.

These concerns include the dependence of CAGRD on excess CAP supplies, which are decreasingly available, and that the recharge will not benefit areas where groundwater is actually pumped, which has impacts on subsidence and localized water availability. PAG's analysis is available in the report and maps linked below in addition to accompanying datasets in raw format from PAG and on the Pima County Map Guide website for interactive viewing.



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