LAKE OKEECHOBEE – “Getting the water right” is a phrase often used by water managers and U.S. Army Corps of Engineers.
Another phrase they often repeat: “most of the time, Mother Nature is in charge.”
With Lake Okeechobee at 15.73 feet above sea level on Jan. 8, the corps is taking a break to review the latest weather forecasts, talk to the scientists and do the math in an attempt to make their best guess on how to manage lake releases between now and the start of the wet season. But corps officials don’t have a crystal ball to predict the actual rainfall and they admit “sometimes, we guess wrong.”
While the “wet season” traditionally runs June 1 through Nov. 30, this is one of those times “Mother Nature is in charge.” The wet season sometimes starts in May. Sometimes the heavy rains start later in the summer. The end of the wet season also varies. In 2019, the wet season was over by September.
Getting the water right is a challenge this year because extremely heavy rainfall in November, with the help of Tropical Storm Eta, dropped 300% of average rain in some areas south of Lake Okeechobee. The water conservation areas (WCAs) south of the Everglades Agricultural Area (EAA) and north of the Tamiami Trail were flooded, and moving that water off the WCAs was difficult due to flooding on the coasts and in the area south of the Tamiami Trail. There was nowhere for the water to go.
By the start of the year, some water was starting to flow under the trail, but the WCAs are still 1-2 feet above schedule. With the WCAs – and the stormwater treatment areas that feed them - already full, water can’t move south from Lake O past the EAA. December brought average rainfall.
Some water will still go south, as needed for water supply, both for the farms of the EAA and for the utilities on the east coast. But on average, that dry season flow south accounts for just about 1 foot of water on lake Okeechobee.
Some water will evaporate into the air or percolate into the earth. Evapotranspiration rates are higher when the weather is hot. For the period from November to June, evapotranspiration accounts for about 1 foot of water on Lake Okeechobee, according to the corps.
That means, unless they can find a way to move more water, Lake Okeechobee will be at 14 feet at the start of the 2021 wet season. That’s a dangerous place to be, with little capacity to hold the wet season rainfall. It’s also not good for the lake’s ecology.
Water managers try to keep the big lake between 12 or 12.5 feet and 15.5 feet above sea level. Nature intended the lake level to slowly fall during the dry season and slowly rise in the wet season. The fluctuation of the lake level is good for the up to 150,000 acres of marshes around the edges of the lake which help clean the water. Lower lake levels allow the submerged aquatic vegetation (SAV) to germinate and grow. If the lake level rises faster than the SAV can grow, it can damage or kill the vegetation.
Thanks to the flood control system that makes it possible for humans to live in areas that were once flooded much of the year, water does not drain slowly into the lake. Before the Kissimmee River was channelized, water that fell just south of Orlando took about six months to sheet flow slowly down into the lake according to the U.S. Geological Survey. Now that hydrological trip takes just weeks.
The integrity of the Herbert Hoover Dike is also a consideration. The corps tries to keep the lake level below 17 feet due to concerns about the safety of the earthen berm that encircles the Big O. Work is underway to strengthen the dike – due to be complete by 2022. Should the dike breach, not only would it flood the towns south of the lake, it would also endanger the integrity of the East Coast Protection Levee, which separates the east coast from the Everglades.
When you think about the lake level, consider the elevations. The City of Okeechobee, which sits on the northern shore of the lake, is 26 feet above sea level. Elevation of cities south of the lake are:
• Clewiston 16.4 feet above sea level;
• Belle Glade, 16 feet above sea level;
• Moore Haven, 13 feet above sea level;
• Pahokee, 13 feet above sea level;
• Canal Point, 13 feet above sea level.
If the dike should ever breach, remember the water runs downhill. Water from the dike could impair the East Coast Protection Levee (which runs from West Palm Beach to Miami), and should that levee fail, consider the elevations of the cities on the other side:
• West Palm Beach, 13 feet above sea level;
• Delray Beach, 8.8 feet above sea level;
• Fort Lauderdale, 9 feet above sea level;
And, just in case you are wondering, the elevations for cities east and west of the lake are:
• LaBelle, 13 feet above sea level;
• Fort Myers, 10 feet above sea level;
• Stuart, 10 feet above sea level;
• Palm City, 7 feet above sea level.
Starting the wet season with a lake level of 14 feet increases the risk the lake could go above 17 feet during the wet season. The drainage from a single hurricane can raise the lake more than 3 feet in a matter of weeks.
In addition, Audubon studies have found: “A Deeper Lake Okeechobee is more dangerous, dirtier, and unhealthy.” An Audubon article by that title published on the Audubon Florida website found “Advocating to hold more water in Lake Okeechobee once repairs are done under the guise of sparing the estuaries and helping the environment is a false and dangerous solution. It’s bad for people, birds, and the environment.”
For now, the corps has halted lake releases to the St. Lucie River and limits releases to the Caloosahatchee to the freshwater flow needed to maintain ideal salinity in the estuaries. That means if it rains in the basin, less or even no water will be released from the lake.
In February, the corps will announce the plan for the rest of the dry season.