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Mayor and Council May 18, 2026 1 MEMORANDUM TO: Mayor and Council THROUGH: Lisette Camacho, Deputy City Manager, (480) 350-8505 FROM: Tara Ford, Public Works Director, (480) 350-2855 DATE: May 18, 2026 SUBJECT: Tempe Water Resources Tempe has a robust and diverse water resources portfolio. In a typical year, the majority of Tempe’s water supply comes from renewable surface water provided by the Salt River Project (SRP). Water previously stored in the aquifer and recovered by Groundwater wells makes up about seven percent of Tempe’s supply, and the remaining six percent is supplied by the Colorado River, which is delivered through the Central Arizona Project (CAP) canal. For the past two decades, the amount of water available from the Colorado River has been steadily declining and at the end of 2026, the collection of agreements and management documents that govern the operation of the Colorado River will expire. These factors create uncertainty regarding how much of Tempe’s CAP supplies will be available in the future. However, Tempe has a culture of conservation, a history of growing sustainably and a robust water resources portfolio that contains sufficient supplies to allow the community to have confidence that Tempe has sufficient supplies to meet all demands, regardless of shortages on the Colorado River. Water Conservation and Efficiency 4.03 Achieve or exceed water conservation targets for Single Family, Multifamily and Landscape customer class water use as measured by gallons per capita per day Groundwater Supply 4.16 Achieve groundwater production capacity to meet the projected average for future daily demand Water Efficiency 4.22 Achieve efficiency gains from 80% of residential and commercial customers participating in Tempe water conservation programs Salt River Project 87% Central Arizona Project 6% Groundwater Wells 7% Tempe water supplies Salt River Project Central Arizona Project Groundwater Wells 2 Mayor and Council May 18, 2026 Since 2015, Tempe’s population has increased by approximately 12%, and during that same period, water demand has decreased by 20%. These reductions in water use over time are due to changes in land use and the collective actions of the community to increase efficiency. To understand how Tempe utilizes available water supplies to meet water demands, it is important to understand the history of Salt River Project. In the late 1800s, local farmers in the valley pledged their land as collateral to build the federally water storage and delivery system that became the Salt River Project. The agricultural lands of these farmers, now largely urbanized, make up the SRP “member lands” in the valley. Due to the structure of the federal project, the water collected and stored behind SRP dams is only available for use on these specific lands. 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000 200,000 220,000 0 10,000 20,000 30,000 40,000 50,000 60,000 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 Population Acre feet Year Tempe total water use and population Water use Population Mayor and Council May 18, 2026 3 In Tempe, these SRP member lands are indicated by the blue areas of the Tempe Water Service Area map. The non-SRP member lands, those that rely on water from sources other than the SRP project member supplies, are indicated by the pink areas of the map. Fortunately, despite a dry winter, the SRP system is not forecasting shortage to future supplies. This is due to the fact that the SRP watershed is not equivalent to the Colorado River Basin. Here in the desert of Arizona, the SRP watershed has become more drought resistant, and SRP’s system has a different allocation system that does not create structural deficits that the system cannot support; and is supported by a robust aquifer and wells to sustain demands in times of drought on the watershed. Historically, Tempe has used supplies from the Colorado River, provided by the Central Arizona Project (CAP) to meet the water demands on Non-SRP member lands. However, in addition to CAP, Tempe has access to additional surface water provided by SRP to meet non-SRP member demands. In the 1990s, Tempe participated in the effort to modify SRP’s Roosevelt Dam. The water stored in the space created behind the dam by these efforts is known as Roosevelt New Conservation Space (NCS) water. In addition to CAP and NCS, Tempe has access to surface water and reclaimed water that was previously stored in the aquifer. Storing water in the aquifer through efforts like this creates Long-term Storage Credits (LTSC). Each of these sources: CAP, NCS and LTSC are renewable supplies that Tempe can use to meet non-SRP member demands within Tempe’s Water Service Area. In addition to Tempe’s CAP supplies, these non-SRP member supplies include 4,200 acre- feet of NCS and the ability to recovery 3,000 acre-feet of LTSC in an average year. As illustrated previously with Tempe’s overall population and water demands, Tempe’s non- SRP member water demands have been decreasing while the population in these areas has been increasing. NCS, 9,000 CAP, 4,493 LTSCs, 3,000 Non-SRP member supplies (acre-feet) Mayor and Council May 18, 2026 4 In addition to reduced water availability from the Colorado River, the seven states that share the Colorado River Basin states and the federal government have yet to reach a consensus on how to manage the river after 2026. With 2027 approaching rapidly, there is significant uncertainty about the amount of CAP water Tempe can expect in both the near and long term. Even basic questions, such as how much of Tempe’s CAP allocation will be available in 2027 remain unanswered. To plan for this extreme uncertainty, Tempe has evaluated a range of possible cuts, or hypothetical shortages to Tempe’s CAP allocations in 2027. The next chart illustrates three planning scenarios and non-SRP member supplies that Tempe is evaluating for 2027. These scenarios range from status quo on the left, which is unlikely given the poor hydrology on the Colorado River Basin this past winter, to no CAP allocation at all on the right. Importantly, note that through all scenarios, there are sufficient supplies available to meet the non-SRP member demands, as indicated by the purple line to the chart. 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 DCP 1 (2025) CAP 85% cut CAP Deadpool Acre-feet Planning assumptions for 2027 2027 Non-SRP member planning scenarios CAP LTSC NCS Projected demand 3,112 2,873 2,917 2,876 2,781 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 18,000 0 1,000 2,000 3,000 4,000 2021 2022 2023 2024 2025 Non-SRP member population Acre-feet Year Non-SRP member potable demands and population Water demand Population Mayor and Council May 18, 2026 5 Looking ahead to 2028, there is the possibility that the federal government will provide clearer guidance regarding availability of Tempe’s CAP supplies into the future years. However, it remains highly likely that Tempe’s CAP allocation will be reduced compared to pre-2027 amounts. The chart below reflects Tempe’s current planning assumptions of non-SRP member supplies and demands. Note that this chart includes a new supply: reclaimed water. Following the rehabilitation of Tempe’s Kyrene Water Reclamation Facility in late 2027, Tempe will have access to local reclaimed water, which can be used to generate Long-term Storage Credits or provide access to new supplies through an exchange with SRP. Although there is considerable uncertainty surrounding the Colorado River, one thing is clear: Tempe is fully prepared to continue supplying the water our community needs to thrive and grow sustainably. To ensure readiness, Tempe actively plans and shares these plans with customers through tools such as concise “one-page” fact sheets and by maintaining an updated Drought Resiliency and Preparedness Plan, most recently revised in 2025. At present, Tempe’s demand management stage within this plan remains at “0, Watch,” reflecting the limited impact that Colorado River shortages currently have on the City’s ability to meet water demands. ATTACHMENT: 2026 Tempe Water Resources Presentation 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 2028 (CAP 85% cut) 2030 2035 2040 Acre-feet Planning year Long-term Non-SRP member planning scenarios CAP Non-Member Groundwater Wells Reclaimed Water Projected Demand