Rethinking Tampa Bay's water resources as the climate changes

Sixth in a series.

Just north of the iconic Big Bend Power Station on Hillsborough County's southeastern shore, the Tampa Bay Desalination Plant processes millions of gallons of saltwater through a teeming maze of pumps and pipes. The final output: fresh drinking water for your tap, to the measure of up to 25 million gallons every day.

Historically, the Tampa region has relied on groundwater pumping for the overwhelming majority of its drinking water. But environmental issues like saltwater intrusion and over-pumping triggered a long series of Tampa Bay "water wars'' between local governments and the state in the 1980s and 1990s. 

As Christopher Meindl, Associate Professor at the University of South Florida St. Petersburg has written, the water wars prompted the creation of a new regional water utility and, with it, a new approach to sourcing the region's drinking water. That entity, Tampa Bay Water, last year (2015) supplied an average of roughly 156 million gallons of wholesale water a day through a 2,000-square-mile water system to some 2.4 million residents living across Hillsborough, Pinellas and Pasco counties. 

About two thirds of the water from your tap still comes from 13 groundwater wellfields scattered across Pasco and Hillsborough counties, where nearly 200 pumps mine the Floridan aquifer. The other third is culled from surface water sources like the Alafia River during Tampa Bay's infamous summer rainstorms. 

The $158 million desal plant, which was the largest saltwater desalination plant in North America when it opened in 2007, provides just 1 percent of the region's water during wetter years like this one (2016). Because it's much more costly to operate, it serves as a backup for drier periods. But it could play a more important role in the future as climate change transforms the region's water supply. 

The science of forecasting local climate change impacts

Today, climate change is prompting scientists and engineers at Tampa Bay Water to revisit and rethink how, where and when the region will source drinking water in the future. 

Tirusew Asefa, Modeling and Decision Support Manager at Tampa Bay Water, points to three particular issues that may impact the region's water supply over the coming decades: changing rainfall patterns, higher temperatures and sea level rise. 

To frame these challenges, Asefa poses a series of questions: "We depend on summer rainfall, 60-70 percent of which comes in just four months. Is there a shift in how we get our summer rainfall? Do we get a shorter summer season? When does it start? How do these flows change 20 or 30 years from now?'' 

Pinning down answers to these hypotheticals is decidedly less straightforward. Over the last several years, Asefa and his colleagues have been working to ''downscale'' a range of global climate models, or GCMs, to the scale of the region's watershed. "We take nationally available climate data and adapt it to local conditions,'' he explains. 

These GCMs generally agree that temperatures in the Tampa Bay area will rise between two and three degrees Celsius (three and six degrees Fahrenheit) over the next half century, which could significantly alter the region's water supply. As temperatures rise, evapotranspiration -- that is, the loss of water through evaporation and plant transpiration -- also increases, Asefa says. Higher rates of evapotranspiration would leave less water for human consumption. 

There is less agreement among GCMs about future rainfall in the Tampa Bay area. According to one Tampa Bay Water research briefing, the projected change in rates between 2039 and 2069 varied from 22 percent less rainfall to 11 percent more. 

Asefa explains that these temperature and rainfall projections -- uncertainties and all -- are put into a hydrological model designed specifically for the Tampa Bay watershed. That model accounts for different natural and man-made variables, ranging from rainfall patterns to groundwater pumping and land uses. 

Future population growth and other changing socio-economic factors are yet another factor in building a portrait of Tampa Bay's future water supply and demand. Using economic and demographic forecasts from Moody's, Asefa and his colleagues estimate how Tampa Bay's anticipated growth will change that equation.

He adds that local sea level rise is also an issue. The operations of the bay front desalination plant and at least one of Tampa Bay Water's surface water collection sites on the Alafia River could be impacted by higher saltwater sea levels.

Tampa Bay Water scientists use these variables to analyze the local hydrological impacts of different global climate change scenarios, and then extrapolate how the region's water supply might change -- and what that means for the utility's day-to-day operations and long-term planning efforts.

But there's still a great deal of uncertainty in the models, making it difficult to make multimillion dollar operational and planning decisions, like when and where to build a new reservoir or desalination plant. 

"When you run these future scenarios through your own model, depending on the time and scale, you may have a different output or result that needs careful interpretation,'' Asefa says.

Managing uncertainty through novel collaborations

To interpret and fine-tune those uncertainties, Tampa Bay Water has adopted a highly collaborative approach. Soon after Tampa Bay Water started to look at climate change in 2007, they elected to join the Water Utility Climate Alliance (WUCA), a national network of 10 of the country's largest water utilities. WUCA's members are working together to translate global climate science into regionally appropriate, actionable water management and climate adaptation insights. 

To date, Tampa Bay Water has collaborated with several other utilities on a number of research initiatives like PUMA, shorthand for Piloting Utility Modeling Applications. Asefa says, "PUMA is an example of how you can co-produce climate

"The biggest challenge for climate scientists is to convey and quantify the uncertainties around forecasts, and to help practitioners to manage that uncertainty,'' says Vasu Misra, an Assistant Professor of Earth, Ocean and Atmospheric Sciences at Florida State University.

information in ways that are useful to your area. The idea was, how can I give feedback to climate scientists, in terms of the data I need and the parameters I use to make actionable decisions?''

Today, Alison Adams, Chief Technical Officer of Tampa Bay Water, chairs WUCA. Soon after joining WUCA, she hatched the idea for a Florida-specific network, and so the Florida Water & Climate Alliance was born. Like WUCA, that organization aims to facilitate learning and dialogue between Florida water management practitioners and climate scientists to develop better longer-term decision-making tools and resources. 

Facilitated by the University of Florida Water Institute, the Florida Water & Climate Alliance includes seven large water utilities and three water management districts (including the Tampa Bay region's own Southwest Florida Water Management District), along with several other academic institutions, and has met quarterly since 2010.

Vasu Misra, an Assistant Professor of Earth, Ocean and Atmospheric Sciences at Florida State University, is a longstanding participant in the project. "The biggest challenge for climate scientists is to convey and quantify the uncertainties around forecasts, and to help practitioners to manage that uncertainty,'' he says.

"We do quite a bit of research at the university, but in order to translate it into products that can be operationalized by utilities, it is quite expensive. The National Oceanic & Atmospheric Administration can't do it for every utility. Utilities are always under pressure to do cost-cutting measures, so they may not be able to find funds to get tailored data when they need it to make decisions,'' he explains.

That's where the Florida Water & Climate Alliance has proved useful in providing a forum for utilities and other institutions to share resources, learn together and advocate for further research. 

"The attendees are curious and very open-minded,'' continues Misra. "We're often coming on our own dime to understand how we can match our research goals to their needs. To be frank, we don't have many such groups around the nation. At the state level, Florida is leading in terms of forming a group like this and meeting regularly. We are finding after meeting 15 times that it is a very difficult task to translate this research into products. But we are hopeful.'' 

For Tampa Bay Water's scientists and engineers, the work of translating global climate science to local action doesn't stop at the state level. Both Adams and Asefa participated on the Tampa Bay Climate Science Advisory Panel, or CSAP, a regional group of scientists that joined forces in 2014. We explored the first outcome of CSAP's collaboration -- a set of regional sea level rise projections -- in the first feature in 83 Degrees Media's climate change series. 

Rethinking water management at the local level

While Tampa Bay Water takes charge for most of the region's drinking water supply infrastructure, local governments are responsible for their own water infrastructure, which also include waste and stormwater systems. 

For communities with a large amount of aging water infrastructure, like much of the City of Tampa and Pinellas County, the increasing severity of neighborhood flooding has become a particularly hot topic of debate and action in recent months. 

In his 2016 State of the City address, Tampa Mayor Bob Buckhorn touted the need for a comprehensive overhaul of the city's stormwater system, which includes over 600 miles of pipe, for example.

In Pinellas County, water management officials are responding to those challenges -- and the looming threat of climate change -- through the development of an Integrated Water Resource Management framework. That's "just sustainability, at it's most simple definition,'' says Kelli Hammer Levy, Natural Resources Division Manager, who has helped to spearhead the project.

Integrated water management, she says, balances natural resources, social systems, the economy and their interconnections. "When you start to disconnect those pieces, you create problems.''

Much of Pinellas County was developed before the state began to adopt more stringent environmental protections like the

In his 2016 State of the City address, Tampa Mayor Bob Buckhorn touted the need for a comprehensive overhaul of the city's stormwater system, which includes over 600 miles of pipe.

Florida Air and Water Pollution Control Act of 1967, leaving entire neighborhoods -- and their infrastructure -- in areas vulnerable to flooding and other issues, according to Levy. That's left the county working to retrofit its water infrastructure in a way that minimizes floods and complies with stricter water quality standards. Sea level rise will only exacerbate these current challenges, she adds.

At the same time, the county has historically divided responsibility for wastewater, stormwater and drinking water management activities across different administrative divisions. Taking an integrated approach to solving water challenges enables these groups to develop collaborative "win-win'' solutions, according to Levy.

To help incorporate integrated water management principles in future projects, Pinellas County has adopted Envision, a civil infrastructure sustainability rating system developed by the Institute for Sustainable Infrastructure. Envision rates the community, environmental, and economic benefits of a specific project on a 60-point scale that reflects a full project lifecycle, from the design process through to long-term maintenance and upkeep.

Levy points to efforts to restore the McKay Creek area in Northern Pinellas County as an example of Envision principles in action. There, Pinellas County and the City of Largo have been gradually restoring the creek's natural floodplain, which extends over more than 5,000 acres. A range of measures -- including the purchase and removal of homes along the creek -- have been undertaken over several years to reduce flooding risks, improve water quality and open up habitat for both recreation and conservation purposes. 

In the future, Envision and other tools like it may also help Pinellas County governments to select climate adaptation investments that offset the vulnerability of specific communities and habitats, as we highlighted in the second feature in the 83 Degrees Media climate change series.

From the regional scale down to individual neighborhoods, and from abstract global climate science models to on-the-ground infrastructure projects, it's clear that institutions across Tampa Bay are beginning to rethink how the region manages its water resources in light of climate change. 

Next week, 83 Degrees concludes this seven-part series with a look at how Floridians' perceptions of climate change are changing, why Florida's cities and regions are leading the way to a more climate resilient future, and how you can take action. Comments? Contact 83 Degrees.

Links to 83 Degrees Media's series of stories on climate change:

Part 1 -- Tampa Bay Area scientists, policymakers plan for rising sea levels

Part 2 -- Preparing for climate change: Pinellas County, local towns take steps to get ready

Part 3 -- Is the global reinsurance industry making Florida more resilient to climate change, hurricanes?

Part 4 -- Tampa Bay real estate boom and climate change: 5 big insights

Part 5 -- Climate change: Across Tampa Bay, environmental organizations mobilize around sea level rise

Part 6 -- Rethinking Tampa Bay's water resources as the climate changes

Part 7 -- Retrofitting Tampa Bay for climate change: From understanding to action