Colorado River Shortage Impact Tool

The Kyl Center’s Central Arizona Shortage Impact Model describes how Colorado River water delivered through the Central Arizona Project canal is allocated under shortage conditions to Colorado River entitlement holders as well as to entities that lease or exchange Colorado River water that belongs to someone else.  Results are presented in acre-feet and represent all Colorado River water available to each entity, be it entitlement, lease, or exchange, under different shortage conditions. These values are shown for amounts of Colorado River water delivered through the Central Arizona Project canal, generally in increments of 100,000 acre-feet.

Entitlement holders and those that gain access to Colorado River water via lease or exchange of another entity’s entitlement include cities, private water companies, Tribes, mining companies, domestic water improvement districts, irrigation districts, power generation companies and others. The information necessary to develop this shortage impact model came from the publicly available contracts between each entity and the Secretary of the Interior that describe the legal terms under which Colorado River shortages are allocated to each entity. Information also came from publicly available leases and exchanges of Colorado River water, which often, but not universally, describe the legal distribution of lease or exchange water under shortage conditions. Legal descriptions were translated into mathematical algorithms. 

The various documents that describe how Colorado River shortages are distributed across entitlement-holders span decades and often contradict each other.  Thus, there is no mathematically correct result regarding the allocation of Colorado River water in Central Arizona under shortage conditions.  Rather, the results presented here are reasonable estimates based on myriad assumptions.  

Entities such as municipal water providers and Tribes often have access to groundwater, local surface water, and reclaimed water alongside Colorado River water. Results presented here are only for Colorado River water availability and should not be interpreted to describe the total amount of all water to which each entity has access.

This tool presents reasonable estimates of the amount of Colorado River water available to entitlement holders of Priority 3 (P3) and Priority 4 (P4) Colorado River water delivered via the Central Arizona Project (CAP) canal during shortage conditions. 

Some entities hold entitlements to a combination of these priorities, and some lease or exchange water of varying priority, as well. How Colorado River water users in Central Arizona are impacted by shortage varies depending on the priorities of the water to which they have access. 

In brief: 

• P4 Excess & Ag Pool: water available only when all entitled demands are met, "leftover" water, generally unavailable during shortage, not included in this tool.
• P4 NIA A: non-Indian ag water allocated before 2021; cut before M&I and Indian priority water during shortage.
• P4 NIA B: non-Indian ag water newly allocated in 2021, but unusable since 2021 became a shortage year with zero prior usage; remains unavailable until a non-shortage year establishes usage.
• P4 M&I and Indian: ~65% M&I / ~35% Indian under shortage (as a rule of thumb); each entity gets contract-specified amounts, shortfalls assumed covered by federal alternative sources or compensation. Cut before P3.
• P3: higher priority than remaining CAP water, includes water settlement transfers; Wellton-Mohawk portion split into its own pool due to cities accepting deeper cuts under the SRPMIC settlement.
• Other Water: Tribal "firming" obligations.