By Ann Henson Feltgen, FloridaBulldog.org
An illustration of saltwater intrusion. Courtesy: floridaswater.com
Saltwater intrusion leading to contaminated drinking water wells has long been feared in South Florida. But, billions spent on measures to protect our water supply — mostly paid for by utilities and their customers — have paid off so far.
The invisible underground barrier separating salt and fresh water is holding saltwater back to the 1995 boundary or even farther east, scientists say.
“This is a success,” said U.S. Geological Survey (USGS) hydrologist Scott Prinos, who helps monitor saltwater intrusion in Miami-Dade County. “The question is: As we move into the future and with population increases, will these measures continue to be effective?”
The barrier between fresh and saltwater — called the saltwater interface — preserves the pristine water in the 3,000-square mile Biscayne Aquifer that supplies potable water to about 5.8 million residents in South Florida and the Florida Keys.
The struggle to forestall saltwater intrusion began in the 1930s when canals were dredged to drain the Everglades, Prions said. As water levels declined in the spongy aquifer, saltwater that is heavier than fresh water, began to flow inland. Population pressure drought, and higher sea levels all play a part in interface movement. Although the interface is stable, it imperceptibly ebbs and flows seasonally.
Florida receives an average of 54 inches of rainfall per year, much of which seeps into the ground and refills the aquifers. This year’s rainy season officially began May 10 and is expected to be above normal in May and June, then below normal through the remainder of the season, according to the National Oceanic and Atmospheric Administration. But those predictions can be trashed by a tropical system hitting South Florida, an agency official noted.
The South Florida Water Management District (SFWMD), which governs potable water for South Florida, has for years been nudging municipalities to control their water usage by adopting conservation measures, installing reverse osmosis plants that can convert the brackish water from the deep Floridan Aquifer into drinking water and storing water during the rainy season for use in dry periods. Last year, these conservation measures were mandated by state law.
Previously, the carrot at the end of the water district’s stick was a water use permit that allows specific withdrawal amounts from the Biscayne Aquifer for up to 20 years. Now South Florida communities and counties are spending billions of dollars to adopt the latest technology and build new facilities, passing along the cost to residents and businesses in increased fees. For its part, the water district has been upgrading and monitoring water control structures that also retard saltwater intrusion, said Pete Kwiatkowski, a SFWMD hydrologist and manager of the resource evaluation section.
The agency also provides substantial grants to cities, special districts and utilities for these projects. The agency issues a request for proposals, then reviews the projects based on a list of criteria and available funding. The projects must be considered nontraditional such as aquifer storage and recovery, reverse osmosis plants and reclaimed wastewater used for irrigation. Since 1997, the agency has approved $1.4 billion in funding for 488 projects.
Broward County offers cities within its borders grants through its Integrated Water Resource Plan.
PROBLEM AREAS WELL KNOWN
Saltwater intrusion hot spots include wells in Lake Worth, Dania Beach, Lantana, Hallandale Beach and Miami-Dade County, which is much more susceptible to intrusion because of its low elevation. Miami-Dade serves as the water utility for the entire county.
“The cities with saltwater intrusion are pretty well known,” Kwiatkowski said. “Saltwater intrusion is not creeping up on us and there are no big surprises.”
One area of concern has been Lake Worth where the saltwater interface moved west because the city was pulling more and more water from the Biscayne Aquifer.
“As part of our 20-year permit with South Florida Water Management District, we had to build three additional wells farther west and abandon five older wells east of I-95,” said Larry Johnson, director of the Lake Worth water utility.
The city also agreed to build a reverse osmosis plant and draw water from the Floridan Aquifer to reduce its reliance on the Biscayne Aquifer.
“We now take half of our water from the Floridan Aquifer,” he said. “Having two sources of water gives us a long-term, sustainable solution. Recent reports indicate that we are controlling the saltwater and the boundary is stable.”
The Floridan Aquifer covers much of the southeast U.S., including Florida, Alabama, Georgia and South Carolina, and is one of the most productive aquifers in the world, according to the U.S. Geological Service. In South Florida, however, the aquifer lies 3,000 feet below the surface and is filled with brackish water.
The Biscayne Aquifer sits above the Floridan Aquifer, just below the surface in Palm Beach, Broward and Miami-Dade counties. Its water is much purer and needs less treatment that water in the Floridan Aquifer.
The cost of the new wells, plants and infrastructure came to more than $30 million. Several million dollars was financed through a state low-interest revolving fund and some of that will be forgiven, Johnson said. Otherwise, the city self-funded the capital project and increased rates to users.
“We raised our [water] rates beginning in 2010 in phases over a period of years,” he said. “Residents are pretty accepting of the rate increases and we worked to keep them at reasonable levels, as compared to surrounding communities.”
Miami-Dade County, which provides potable water to 2.6 million residents, businesses and visitors, launched a capital improvement program for water and wastewater projects two years ago.
The $4.1 billion potable water plan includes replacing a 100-year-old reverse osmosis plant in Hialeah that the county co-owns with the city of Hialeah, building another reverse osmosis plant in the southern part of the county that will draw water from the Floridan Aquifer and shutting down five small well fields, according to Doug Yoder, deputy director of operations for the Miami-Dade County Sewer and Water Utility.
“Those well fields were built in the 1920s, 1950s and 1960s,” he said.
The projects were mandated by the county’s water use permit, approved in 2012.
“We are funding these projects through the state revolving loan fund that we pay back,” he said. “That’s our only source of revenue outside of our own funding.”
The county as well as other counties and cities do receive grants from the South Florida Water Management District for water conservation activities that encourage people to use less water and gives rebates for fixtures that are low flow, such as toilets and shower heads, he added. Miami-Dade County receives about $25,000 per year for these efforts.
Customers are covering the project costs through a 6 percent rate increase put into effect last year and another 6 percent increase recommended for this year’s budget. “We have had few if any complaints about the increase,” Yoder said.
Yoder said the county might apply for a grant from the SFWMD for its reverse osmosis plant when it is to be built.
Sometimes changes made by a water utility can come at little or no cost as was the case with Lantana, said Jerry Darr, director of the city’s water utility.
“South Florida Water Management District noticed that our salinity was increasing and suggested we shift our water draws to wells farther west,” he said. “The eastern wells are still operating, but we just use them less so we don’t lose them.”
The cost to the city and customers was negligible, he said.
WHAT ABOUT THE FUTURE?
Much has been said about the effects of climate change and what it may mean for South Florida’s potable water supply.
Eric Draper, executive director Audubon of Florida
“It’s too early to declare a victory over saltwater intrusion,” said Eric Draper, executive director of Audubon Florida, which supports and stresses conservation of natural resources including water. “Saltwater intrusion is also a matter of sea level rise and we don’t know what will happen.”
He said water use projections are fairly flat and water managers have done a good job in instituting conservation measures, especially Cooper City, which won the Audubon’s water conservation award last year.
“As sea levels rise, it puts more pressure to move the saltwater that’s underground. I don’t know if we have studied that yet,” he added.
Barry Heimlich, a retired engineer for the petroleum and pharmacology industries who now devotes time to warning of the impact of saltwater intrusion, is concerned about the Biscayne Aquifer. While he acknowledges that much has been done, more actions could be taken, he said.
“As the sea level rises, saltwater pushes inland like a parabolic curve – the deeper you go the more saltwater there is and it moves inland,” he said. “Some wells have become contaminated and were moved inland and that will probably continue. Even a small amount of sea rise can have a very large effect.”
He worries that rising sea levels will not only submerge coastal cities in saltwater, it could “flow north and contaminate the headwaters of the Biscayne Aquifer,” Lake Okeechobee.
Scientists agree that climate change is a factor, but say efforts are taking place to save the aquifer and, as technology continues to advance, more strategies will come into play.
USGS’s Prinos said South Florida governments are working together to identify areas of concern and come up with proactive solutions.
“We maintain salinity control structures, relocate wells that are very close to the coast farther west and we are using [best] practices with water conservation and some cities are using reclaimed water for irrigation,” he said.
Dorothy Sifuentes, also a hydrologist with the USGS, said some municipalities in South Florida are looking at aquifer storage and recovery as another means to stabilize the aquifer. “Some are considering, discussing and planning the idea of storing water from the rainy season for later use,” she said.
She added that the four South Florida counties have banded together in a coalition that is concerned about water resources as well as climate change.
The Southeast Florida Regional Climate Change Compact was formalized following the 2009 Southeast Florida Climate Leadership Summit. Elected officials came together to discuss challenges and strategies for responding to the impacts of climate change, according to the agency’s website. The compact outlines ongoing collaborative efforts among the compact counties (Palm Beach, Broward, Miami-Dade and Monroe) to foster sustainability and climate resilience.
“They are developing a regional approach to this resource,” Sifuentes said.
Prinos added that technology now allows pinpointing where the saltwater interface is and if it is moving east or west. During mapping in 2011, the agency deployed helicopters equipped with electromagnetic technology that can precisely determine where the interface is located. Formerly, the salinity in sentinel wells along either side of the interface was used to determine if saltwater was moving.
“In some cases, we had the front farther west than it really was,” he said.
“As we move into the future, we will continue to be vigilant, watching and considering ways to hold it back.”
Ann Henson Feltgen can be reached at firstname.lastname@example.org