Eloy and Maricopa-Stanfield (EMS) Basin Study


The Eloy and Maricopa-Stanfield (EMS) Basin Study is located in Central Arizona within the Arizona Department of Water Resources (ADWR) Pinal Active Management Area (Pinal AMA). Water demand in the Pinal AMA has historically been dominated by the agricultural sector. Pinal AMA management goals include: continue to develop non-irrigation water uses, support the agricultural economy as long as feasible, and preserve water supplies for future non-irrigation uses. In 1987, the Central Arizona Project began delivering Colorado River supplies to the Pinal AMA and surface water supplies replaced groundwater mining. If a water shortage is declared, surface water supplies may be reduced, leading to increased groundwater pumping. To address water supply uncertainties, the EMS Basin Study will assess current and future water demands and supplies and develop strategies to help ensure future water supply sustainability. The EMS Basin Study will be a technical assessment and will not make statements of policy or future commitments by Reclamation or its cost-share partners.

Cost-share Partners: Pinal Partnership Water Resources Committee; Central Arizona Project; Arizona Department of Water Resources (ADWR); Pinal County; Pinal County Water Augmentation Authority; Global Water Resources, Inc.; Arizona Water Company; Cities of Casa Grande and Eloy; and Maricopa Stanfield Irrigation and Drainage District.

Study Area: The EMS Basin Study area encompasses sub-basins identified by ADWR as the Eloy and Maricopa-Stanfield sub-basins of the Pinal AMA in Pinal County, Arizona.

Study Objectives:
• Compile water demand and supply data and develop future demand projections.
• Select relevant climate change scenarios.
• Update the ADWR Pinal AMA Groundwater Model to evaluate groundwater conditions.
• Compile information and analyze infrastructure needs and vulnerabilities.
• Formulate and assess adaptation and mitigation strategies to address water supply vulnerabilities.
• Complete an Economic Analysis and prepare a Final Report.

Stakeholder/Public Involvement: The Pinal Partnership is the lead for stakeholder involvement. A
Stakeholder Advisory Team will be coordinated through the Water Resources Committee.

Cost: The total cost of the 3 year study is $1,360,000. Cost-share partners will contribute $680,000 of
in-kind services. Reclamation will contribute $680,000 for work completed by Reclamation or its

Contacts: Valerie Swick, vswick@usbr.gov 623-773-6272
Jake Lenderking, jake.lenderking@gwresources.com 480-719-6977

Documents: (meeting documents found in separate sidebar)
Memorandum of Agreement
Plan of Study
Basin Study Proposal
Basin Study Directives
ADWR Groundwater Flow model report

Latest news:
Pinal Partnership, Reclamation begin groundwater study
Pinal Partnership moves forward with Basin Study

More EMS Basin Information