Application of GIS to Plan Long-Range Water Supply Facilities by Linking Land Use and Water Billing Data of City of Cape Coral in Southwest Florida

This paper describes the application of a land use based approach to prepare a long-range forecast of water supply demand for the city of Cape Coral in southwest Florida. There are two common approaches to forecast water demand: (1) use of population projections; and (2) analysis of future land use planning. The South Florida Water Management District (SFWMD), as required in 2002 Legislation, has made the land use approach mandatory with the intent to improve the coordination of water supply planning and land use planning in local government comprehensive plans. Compared to the traditional population based approach, the land use based approach can more accurately capture water demand trends depending on future development, as designed in local government comprehensive plans. This land use based approach is applied to mitigate the uncertainty of population growth models. Especially in Southwest Florida, rapid population growth and the resultant rapid increase in water demand due to immigration have generally exceeded the projections of earlier water supply plans. This paper describes a planning approach using GIS to link current land use and water billing data in order to determine the current and future water demand ratio per acre by land use type. Based on the future land use planning identified in Cape Coral's comprehensive plan, the future water demand in 2020 is projected using land use codes at a projected 68.4 percent build-out. A comparison of water demand (produced) forecasts from the land use based approach and the population based approach as developed in the Cape Coral's 2004 Facilities Planning Report is also conducted. For the planning period through year 2030, the land used based approach yields higher average and maximum daily water demand (produced) projections than the population based approach. For the projection after 2030, the land use based approach yields lower water demand (produced) projections than the population based approach because the population would not keep growing as rapidly as it does at the beginning of developing period. The land use based approach could provide more accurate projections of demand curves for public water supply as compared to the traditional population based approach of extrapolating population growth curves multiplied by assumed per capita consumption.