Scientists trying to unravel the mystery of Everglades plumbing turned a marsh west of Miami neon green Tuesday after releasing millions of gallons of dyed water into a swath left parched for the last half century.
The massive $10 million experiment, in the works for about eight years, should help hydrologists better understand how to reconnect sections of the Central Everglades carved decades ago into a network of flood-controlling canals, levees and other structures. For the next three months, scientists will record the movement of water, its depth and speed as well as amounts of sediment and harmful nutrients like phosphorus, to study how its flow helps define the complicated topography of ridges, sloughs and tree islands.
Biologists will also track the surrounding ecosystem — the fish, wading birds and thick mats of vegetation — to find out what it takes to improve life in the nation’s largest ecological restoration project.
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“You can do experiments in the lab, but until you get out in the field, you don’t really know what’s going to happen,” said Barry Rosen, a biologist with the U.S. Geological Survey and one of the project’s chief scientists.
On Tuesday, the scientists released the dye in a two-by-two-mile wide area known as the Pocket just north of the Tamiami Trail between two canals and twin levees. The canals were constructed in the 1960s to control flooding in towns to the east, such as Sweetwater. Minutes after South Florida Water Management District wetland scientist Eric Cline added the dye in the canal, a bright green blob bloomed in front of culverts connecting it to the marsh. About a half hour later, the dye could be seen floating through the sawgrass and rolling south down a slough.
Like a lot of other canals crisscrossing the Everglades, the L-67A and L-67C choked off the natural sheet flow of water that nourished the marshes and created the ridges and sloughs that filled in the wet season and slowly receded in dry months to concentrate fish and other prey for a thriving community of wading birds.
“If you have this highway of flow,” Rosen said, referring to the canals, “you move water straight down and it doesn’t do what it’s supposed to do.”
Marshes in the Pocket, fed only by rainfall and some water seeping from the canals, dried out and became prone to wildfires that eroded the land even more.
“It takes a thousand years to make an inch of soil and that’s gone in a flash,” said Fred Sklar, a scientist with the South Florida Water Management District.
Moving water south is the central component of the Everglades restoration authorized by Congress in 2000. But how that water is moved — and how segments of the vast ecosystem are restored and rejoined to the whole — have frequently sparked outrage from competing interests. Anglers want to keep bass-rich canals flowing, and the Miccosukee tribe has fought for clean water. Farmers need dry fields. Neighboring cities want flooding controlled.
To help balance demands, Sklar, who advises the U.S. Army Corps of Engineers on environmental matters, suggested running a large-scale model to see more precisely what happens.
“You can’t build all that you want into a project up front because it’s not just an engineering question,” he said. “It’s also a biological question.”
So last year, after reworking the design to appease anglers, workers inserted 10 culverts into the western canal and removed the levee that runs along the eastern canal. They removed the levee on the eastern side to allow water to continue flowing and also plugged and filled portions of the canal to study whether some canals could remain partially open to allow fishing.
On Tuesday, workers used drills to open gates on the culverts, allowing about 10 times as much water to flow into the Pocket, close to historical levels. Biologists then added fluorescein, the same harmless dye injected into eyes during vision exams, and watched it spread. Within minutes, water that had only been moving at about .08 inches per second jumped to 1.2 inches per second. The gates will remain open until the end of December, although Rosen said scientists are hoping to extend the experiment into January. Gauges spread throughout the study area will also monitor water quality as well as measure the velocity and level of sediment.
Results of the experiment will “essentially inform what will happen later,” said Lt. Col. Tom Greco, the Corps’ deputy district commander for South Florida. “Before we spend millions on structures, you want to [know] as much as humanly possible.”