Rain, New Water Sources Help Wetlands Recover
by Donald J. Polmann, Ph.D., P.E.

New sources of water and new technology for pumping, combined with a combined with a wet winter and a prolific rainy season, have helped raise water levels in the Floridan Aquifer to their highest levels in 14 years near many Tampa Bay Water wellfields.

With the aquifer at record high levels, water level recovery in lakes and wetlands will follow, says Warren Hogg, a hydrologist for Tampa Bay Water. "Lakes and wetlands are subject to so many other influences, such as drought and surface water drainage changes, that it's hard to document changes and their causes," he adds. "But they'll be evident in time."

Along with rainfall, the aquifer's recovery can be traced to an 1998 agreement between Tampa Bay Water and the Southwest Florida Water Management District that allowed Tampa Bay Water to develop new sources of water and cut back pumping from an average of 158 million gallons per day (mgd) to an average of 121 mgd at certain wellfields by the end of 2003 and to 90 mgd average by 2008.

Last year, Tampa Bay Water began operating new water supply projects to replace water that had been previously provided by certain older wellfields. A surface water treatment plant has been harvesting and treating water from the Hillsborough and Alafia rivers and the Tampa Bypass Canal during high flows for nearly a year. The Brandon Urban Dispersed Wells project, a redeveloped groundwater project, has been operating without environmental harm since January 2001. The Tampa Bay Seawater Desalination Plant, currently in an extended start-up period, is expected to be in full-time operation by the end of the year.

"Some say that the increased aquifer water levels are a result of the rain, but that's only a part of the story," Hogg said. "Heavy rainfall allowed us to shift production to an extent that was not anticipated. That meant we could cut back on groundwater pumping at over-stressed wells, and as a result, we are already seeing signs of environmental recovery. Had we not delivered our new, non-groundwater water projects on time, we would not have been able to cut back on groundwater pumping."

Tampa Bay Water is ahead of schedule on its pumping reductions, according to Hogg. The utility is required to meet a 121 mgd pumpage limit as a 12-month running average to be measured in January 2004, but is already down to 99 mgd. But what really happened to the environment around groundwater wells, and is recovery on the horizon?

"There's significant misunderstanding about groundwater supplies," said Kathleen Coates, Tampa Bay Water project manager. "Groundwater is not inherently bad-with today's technology for designing, building and operating wells, groundwater can be safely withdrawn without causing environmental harm." Pumpage-related effects on lakes and wetlands, Coates said, occurred around many long-producing wells-some that have been operating for 70 years and were designed and built prior to state environmental permitting regulations. These older wells were also designed without the benefit of newer technology that is now available to help avoid environmental impacts.

"It's not surprising that we saw impacts around wells that were designed many decades ago," she said.

But are these cutbacks sustainable?

Hogg says they are. "Tampa Bay Water has invested $610 million in alternative supplies to offset pumping reductions while still meeting the region's needs. We've diversified our system with surface water, we're building a reservoir to store surface water, and the desalination plant is scheduled to be in full operation by the end of the year. We now have enough new sources to meet the region's needs in an environmentally sensitive manner."

Dr. Polmann is director of science and engineering at Tampa Bay Water, Florida's largest wholesale water supplier. It develops and supplies drinking water to its members-Hillsborough, Pasco and Pinellas counties and the cities of New Port Richey, St. Petersburg and Tampa. They, in turn, provide water to nearly 2 million customers