A report in some coastal media that the C-44 reservoir was holding “80% less water than it should,” seems to have missed the point of the C-44 reservoir.
A story published Oct. 9 by T.C. Palm and Oct. 10 by the Palm Beach Post stated: “The C-44 reservoir’s water level has been kept at 3 feet instead of 15 feet since March, meaning it’s holding about 3.26 billion gallons of water instead of 16.5 billion gallons – about 13.2 billion gallons less than it should be.”
Water managers never intended to try to keep the reservoir at full capacity. How much water the reservoir “should” be holding depends on how much rain falls in that basin. During the past wet season, the reservoir had more than enough capacity to handle the excess rainfall.
Unlike the EAA reservoir and the Lake Okeechobee Component A Reservoir (LOCAR), the primary purpose of the C-44 reservoir is not to store water for use in the dry season. The primary purpose of the C-44 reservoir is to protect the St. Lucie Estuary, by preventing nutrient-rich C-44 basin runoff from being released through the St. Lucie Lock. How much water it “should” be storing depends on how much runoff there is.
If they filled the C-44 reservoir to capacity – which they could easily do, using water from Lake Okeechobee – the reservoir could not fulfill its primary purpose of protecting the estuary. While 16.5 billion gallons seems like a big number, it’s less than 2 inches on the Big O. One inch on Lake Okeechobee is about 12 billion gallons.
Before the reservoir was built, if Lake Okeechobee’s level was below 14 feet above sea level, excess water from the St. Lucie Canal (C-44 canal) could backflow into Lake Okeechobee at Port Mayaca. If the Lake O level was above 14 feet, that was not an option as the water control structure is gravity flow. So if the lake level was 14 feet or higher, runoff from heavy rainfall in the C-44 basin had to be released east through the St. Lucie Lock. This disrupted the salinity balance in the St. Lucie estuary. The runoff from the C-44 basin is also high in nutrients. Data in the South Florida Environmental Report shows the C-44 runoff is higher in phosphorus and nitrogen than the water from Lake Okeechobee. That nutrient load was disruptive to the St. Lucie River’s ecology and could contribute to cyanobacterial blooms (commonly called blue-green algae).
U.S. Army Corps of Engineers (USACE) keep the C-44 canal between 14 and 14.5 feet above sea level for navigation, flood control and water supply. The minimum level is around 12.6 feet – this would only happen in a drought when Lake Okeechobee is that level or lower.
With the reservoir in place, when heavy rainfall in the C-44 basin threatens to push the C-44 canal above 14.5 feet, the excess water is pumped into the C-44 reservoir. From the reservoir, it can be cleaned in the C-44 reservoir stormwater treatment area (STA) and returned to the canal when water levels drop.
During the past wet season, the reservoir was used for this purpose. It worked. The reservoir is currently rated to go up to 10 feet. It had plenty of capacity. The reservoir’s highest level during the 2023 wet season was around 7 feet.
The original design for the reservoir would allow water levels up to 15 feet. During the testing phase, using lake water to fill the reservoir for the tests, USACE discovered a few spots on the bank of the seepage canal which surrounds the reservoir were “muddy,” making them hard to mow when the water level was above 10 feet. Their research into this issue uncovered unexpected differences in the geology of those areas. While they had taken core samplings before the work started, they could not sample every inch of the project area. Unique geological conditions meant the ground water levels rose in the “muddy” areas. They plan to address this problem by installing seepage wells.
In the meantime, they will keep the reservoir at 10 feet or below. If a heavy rain event occurs when the reservoir is at capacity, they can let the excess water out the St. Lucie Lock, as they did before the reservoir was built.
One thing to remember: This is not a natural system. Mother Nature did not connect Lake Okeechobee to the St. Lucie River and Mother Nature did not connect the St. Lucie River to the ocean. Those connections are manmade. These manmade water control systems brought unexpected consequences in the past, and despite modern technology, there will likely be unexpected consequences in the future. Fortunately, it appears the engineers are getting better at identifying and dealing with these problems.