Cypress Lake Transmission Project: Regional Cooperation to Wheel Alternative Water Supplies

摘要

Five major Central Florida utilities came together to cost effectively develop and share a regionally significant alternative water supply source: brackish groundwater from the Lower Floridan aquifer near Cypress Lake in southern Osceola County. This paper summarizes the conceptual design for the transmission and optimization of the Cypress Lake Project water supply in concert with existing potable water sources to facilitate the efficient transfer and transmission of potable water among the five utilities. The primary goal of this project was to develop a cost effective and reliable strategy to "wheel" existing water supplies between the utilities and transmit and integrate water from the Cypress Lake Project into the Utilities potable water distribution systems. In 2007, the City of St. Cloud (STC), Toho Water Authority (TWA), Orange County Utilities (OCU), Polk County Utilities (PCU), and Reedy Creek Improvement District (RCID) initiated planning for the Cypress Lake Project and were subsequently issued a 30-year 37.5 million gallons per day (MGD) water use permit by the South Florida Water Management District to withdraw groundwater from the Cypress Lake wellfield. To further the cooperation in 2011, an interlocal agreement was executed establishing the Water Cooperative of Central Florida with STC, TWA, OCU and PCU as members. The Water Cooperative of Central Florida, together with RCID, have completed a conceptual design of the Cypress Lake Project transmission system to deliver 30 to 36 MGD of finished (potable) water, considering the estimated recovery associated with lowering the dissolved solids of the brackish supply. This overview discusses how the challenge of evaluating the future water supply and transmission needs of five collective utilities while maintaining individuality and unique hydraulic and water quality constraints was met. Another key challenge was estimating the capacity of existing facilities to supply future peak flows for a potentially average flow (base-loaded) supply from the Cypress Lake Project. These challenges were met through the development of two innovative modeling applications, 1) a regional hydraulic model of the five utilities' potable water distribution systems and 2) a water supply model to predict the peak demand and conjunctive use needs of the project. These tools were used to provide the Water Cooperative of Central Florida key information to make informed, evidence-based decisions regarding project directives. This effort demonstrates that by proactively and regionally cooperating to achieve optimal use of existing supply sources while efficiently integrating alternative water supplies, the Water Cooperative of Central Florida utilities are saving millions of dollars compared to implementing individual transmission systems to convey water from the Cypress Lake Project.