Resource-planning CIP allocation:

Traffic and census tract population projections are analyzed using ArcGIS to estimate future potable water demands for the City of Tucson, Arizona. The estimated demands are applied to Tucson Water’s current hydraulic model using Haestad Methods’ WaterGEMS software. The model is then used to determine what facility and piping modifications will be required to meet growth within current service areas and future development in outlying areas. Using capital and energy cost estimation tools within the hydraulic modeling software, different planning scenarios can be compared as to their overall costs. ________________________________________________________________________ Introduction Tucson Water currently serves water for the greater Tucson area, as well as outlying areas within Pima County, Arizona. Where, when, and how the current distribution system expands is greatly dependent on where new housing developments are built now and will be in the future. Population projections generated through the use of census data and water service area boundaries are used in conjunction with a projected future boundary to determine what facilities and piping will be needed, when, and where. In an effort to determine costs associated with changes and additions to the water system network, hydraulic models of the water system were used with projected spatially correct future demands, based on US census population projections for years 2030 and 2050. With these demands properly distributed within the current water service area zone boundaries, the hydraulic models estimated capital costs and energy costs associated with changes or additions to the current water system needed to provide adequate water supply, adequate water pressure, and necessary fire flow to future service areas. For the most recent planning efforts performed in 1989, a similar process was conducted manually using ‘flat’ population projections. Planners and engineers calculated how much of the county Tucson Water served in the past and then expanded this percentage into the future, based on a projected population for the county. This process gave a good estimate of total volume, but it was not spatially distributed. With the advance of GIS tools, spatially distributed dis-aggregated population projection data, and advanced hydraulic modeling software we have developed a better method for projecting expansions and additions to the water infrastructure to accommodate new development within our predicted service area. Tucson Water’s potable system served over 180,000 services, maintained over 4000 miles of pipe, and installed over 500 new meters per month at the time this paper was written. Tucson Water also served reclaimed water to over 550 reclaimed services, maintained over 100 miles of reclaimed pipe, and installed between 75 and 100 new reclaimed meters per year. ________________________________________________________________________