The winds and outer bands of Hurricane Irma are long gone, but as rainwater drains south through Florida’s rivers and watersheds, the storm still presents a slow-moving crisis headed right for Lake Okeechobee.
The hurricane dumped a lot of rain upstream of the lake--according to the National Weather Service in Melbourne, the two-day total in Ft. Pierce alone was more than 21 inches. As Irma’s rainfall reaches Lake Okeechobee, the increasing water level could cause problems with the aging Herbert Hoover Dike--a 143-mile earthen dam that surrounds the lake, parts of which were built in the late 1940s.
According to Mark Perry, the executive director of the Florida Oceanographic Society in Stuart, the water levels in Lake Okeechobee are already on the rise from Irma’s rains. “We’re going to still see that effect for several weeks going forward,” says Perry.
Nearly $900 million has been spent to reinforce the dike since 2001. That work includes installing a partial cutoff wall along the southeast part of the dike and removal and replacement of water control structures such as culverts. A Lloyds of London analysis shows more than 400,000 residents and their homes and businesses would be at risk if the dike were to fail.
It’ll be a few weeks until the water that fell in north and central Florida travels through the Kissimmee River into lake Okeechobee.
“Irma dumped an awful lot of precipitation not only over the lake but in the watershed to the north and west of the lake,” says John Campbell, a public affairs specialist with the Army Corps of Engineers in Jacksonville, which maintains the dike and manages the lake.
Campbell says there was little damage due to Irma’s pounding, “just a little bit of minor erosion in some areas that you would see with any heavy rain event. The dike is fine, we are keeping our eyes on the water levels in the lake.”
For that reason, Campbell says the Army Corps has started releasing water into the St. Lucie River. The Corps is trying to time these releases to coincide with low tide so flooding doesn’t result for residents downstream of the St. Lucie lock and the dam west of the turnpike in Martin County.
Before the hurricane, says Campbell, Lake Okeechobee’s water level was at just under 11 feet. Now it’s up to 14 feet.
“We think it’s going to, just from this event alone, it’s gonna go up to 17 feet or close to it--and if it got to 17 feet, that will be the highest it’s been in over 10 years,” says Campbell.
“Let’s look at it this way, one foot on Lake Okeechobee is 152 billion gallons,” says Perry of the Florida Oceanographic Society. “Take five days at 30 billion gallons a day, you’ve raised the lake by one foot.”
There may be other big problems says Perry. Irma’s rains decreased the salinity levels in the Indian River Lagoon to zero. Lake Okeechobee water releases keep those salinity levels from returning to normal.
“If that continues for more than 28 days for oysters, or nine days [to] 12 days for seagrass habitat,” says Perry, “then we’re going to see some damage to the habitat itself.”
But there are risks to not releasing the water off Lake Okeechobee. For each foot the lake rises above 15 feet, the chance of the dike failing increases. Should it ever reach the 21-foot mark, the probability nears 100 percent. Perry says there are mitigation programs in progress to help keep the water from reaching that mark, but they are years from being ready to institute. For now, water releases from the lake are the only option.