By BOB MALIVA
Florida is blessed with abundant high-quality fresh groundwater that is suitable for potable use with only minimal treatment. However, the water demands from the enormous population growth in the greater Tampa Bay area have long ago reached the limits of sustainable production from freshwater aquifers. Excessive pumping was causing unacceptable environmental impacts to wetlands and lakes, land subsidence and the degradation of water quality by saline water intrusion.
The late 1980s and early 1990s saw the establishment by the Southwest Florida Water Management District (District) of the Northern and Southern Water Use Caution Areas with goals of ensuring that water supply needs are met for existing and projected reasonable and beneficial uses and achieving recovery of groundwater levels so that minimum environmental flows and levels in lakes and rivers are met and saltwater intrusion is minimized.
The District, Tampa Bay Water and local utilities have done a commendable job working together toward reducing overall fresh groundwater pumping. The current diversified system, which blends groundwater, surface, or river, water and desalinated seawater, has been operating successfully for more than 20 years and environmental effects from past practices have all but disappeared. However, recent drought conditions reveal the vulnerabilities of the region’s water supply.
The population of the region continues to rapidly increase. The medium population projection of University of Florida Bureau of Economic and Business Research for Hillsborough, Manatee, Pasco and Pinellas counties has their combined populations increasing from approximately 3,657,800 on April 1, 2025, to 4,307,200 20 years later in 2045. Water will need to be provided for another 649,400 people. The projected increase in population is close to the entire current population of Pasco County.
The primary sources of potable water in the region are groundwater and surface water. Tampa Bay Water currently obtains approximately 53 percent of its supply from groundwater, 43 percent from river water, and four percent from desalination. Some additional surface water is available, but withdrawals are limited by regulatory minimum flow requirements in rivers. Expensive storage (reservoirs) is needed to store seasonally captured water for reliable year-round supply.
Water utilities can access additional fresh groundwater for potable supply through aquifer recharge or the transfer of existing groundwater pumping. For example, farmlands may be purchased with the intent of using the amount of water historically used on the farm for potable supply, with the requirement that there be a net benefit that offsets the impact of the proposed withdrawal. An additional positive effect on the water body equal to or exceeding 10 percent of the predicted offset impact is required.
Reuse of reclaimed water for non-potable uses can make higher-quality sources available for potable use. Most wastewater reuse in Florida occurs by golf courses and parks and for residential irrigation in some new communities where dual-piping is installed at the time of construction. The cost to retrofit existing communities for residential reuse is usually prohibitive. Wastewater that would otherwise be disposed of by offshore outfalls or deep well injection is being increasingly put to beneficial use for aquifer recharge (e.g., South Hillsborough Aquifer Recharge Project; SHARP). Credits obtained for aquifer recharge using treated wastewater or surface water can be used for additional fresh groundwater withdrawals elsewhere.
The SHARP water will not enter the potable supply. The next step in wastewater reuse is potable reuse, whereby wastewater recharged to an aquifer will enter the potable supply. Potable reuse requires a much higher level of treatment, with associated costs, and may face public opposition. However, as water shortages become more acute, potable reuse projects may become more economically and politically viable.
Any community with access to the coast has an essentially unlimited supply of water available through desalination. The Tampa Bay Seawater Desalination Plant, the second largest seawater desalination plant in the United States, produces up to 20 million gallons of high-quality drinking water per day. However, seawater desalination is energy-intensive and thus expensive. Desalination of brackish groundwater is less expensive, and numerous facilities have been constructed or are under development in Florida, including systems in Clearwater, Tarpon Springs and Dunedin.
The Tampa Bay region, and Florida as a whole, has long ago harvested the “low-hanging fruit” as far as reliable and inexpensive potable water. The future will likely be a continuation of the past two decades or so — additional water to meet population growth will be obtained from diverse alternative sources, including reallocations, wastewater reuse, desalination, some additional surface water use and managed aquifer recharge.
Bob Maliva, is Principal Hydrogeologist for WSP in the United States.
