WaterAquifer Storage and Recovery should be phased in to reverse Everglades decline

Although uncertainties about ecological impacts are too great to justify near-term, large-scale implementation of aquifer storage and recovery (ASR) in the Everglades, ASR could be phased in to answer several important scientific questions and provide some early restoration benefits, says a report from the National Research Council (NRC) that reviewed a study by the U.S. Army Corps of Engineers and the South Florida Water Management District.

The NRC says that aquifer storage and recovery is a key component in the Central Everglades Restoration Plan (CERP), a joint state-federal effort to reverse the decline of the Everglades ecosystem. CERP aims to “get the water right” by improving the quantity, timing, and distribution of water flows. Over a century of canal drainage and water management has led to extensive losses of natural water storage, leaving the Everglades in critical need of new storage.

CERP included a project to drill over 330 aquifer storage and recovery wells that during wet periods would pump up to 1.7 billion gallons of surface water per day underground for later use during dry periods.

To address uncertainties about regional effects of implementing ASR on a large scale in the Everglades, the U.S. Army Corps of Engineers (USACE) and the South Florida Water Management District conducted an 11-year ASR Regional Study to assess how aquifer storage affects water quality and whether the recovered water poses ecological risks. Through modeling simulations, the ASR Regional Study concluded that the number of ASR wells in the region that can be operated without exceeding well pressure constraints is much lower — about 131 wells — than originally envisioned in the CERP. At the request of USACE, the National Research Council convened a committee of experts to review the ASR Regional Study and to assess progress in reducing uncertainties about large-scale implementation of ASR.

The ASR Regional Study significantly advances understanding of large-scale implementation of ASR in south Florida, the National Research Council report says. The committee agrees with the ASR Regional Study findings that no “fatal flaws” in ASR have been discovered.

However, many uncertainties remain that merit additional study before large-scale ASR should be implemented, the report says. For example, storing and recovering water can change its chemistry, and research on the risks of exposing plants and animals to water that has been stored in the subsurface suggests some cause for concern. A more detailed understanding of the quality of recovered water and potential ecological risks is needed, including the effects of longer storage times and different operating conditions. 

Further assessment is also needed of the cost and performance of ASR compared with alternatives and the potential benefits ASR may provide by removing phosphorous from water over the long term.

These and other high-priority uncertainties can be resolved through research at a range of scales, from computer modeling and laboratory testing to continued pilot testing to expansion of the current pilot sites. Until the uncertainties related to ecological effects are largely resolved, any new ASR wells to be drilled should be sited adjacent to large water bodies with adequate mixing zones to minimize adverse ecological effects, the report says.

NRC notes that the study was sponsored by the U.S. Army Corps of Engineers Jacksonville District and the South Florida Water Management District.

— Read more in Review of the Everglades Aquifer Storage and Recovery Regional Study (National Academies Press, 2015)