This is the first update to Water Plan: 2000-2050 since it was issued by the City of Tucson's Water Department (Tucson Water) in 2004. The substantive issues and challenges to ensuring a secure water future remain largely the same (they and are discussed at length in the original Water Plan: 2000-2050). However, the planning time frames within which to address these challenges have changed and are discussed in this update. This update also accounts for revised population projections that have since been developed, an increase in the city's Central Arizona Project allocation, and changed planning assumptions and priorities that evolved in the last three years. These include a greater recognition of the potential long-term impact that climate change may have on the utility’s available water resources, and the community’s annual and seasonal demand for water. Specifically, Section Four, "Available Water Resources," discusses factors that could contribute to future shortages on the Colorado River, including effects of extended drought conditions on water availability, and potential ramifications of long-term climate change.