PORT MAYACA — For most of the rainy season, water from the St. Lucie Canal, also called the C-44 Canal, “backflowed” into Lake Okeechobee. The U.S. Army Corps of Engineers tries to keep the C-44 at 14 to 14.5 feet above sea level. When the canal level is higher than the lake level, if the Port Mayaca gate is open, water from the C-44 backflows into the lake.
Historically, according to South Florida Water Management District data, the runoff from the basin that drains into the C-44 has been about twice as high in phosphorus as the lake water. If there is an algae or cyanobateria (called blue green algae) bloom in the lake, the nutrient load will help to feed the algae.
This year, there is another factor to consider. Last week, Florida Department of Environmental Regulation documented streaks of what appear to be blue green algae in the C-44 Canal near the St. Lucie Lock.
The recent rapid rise of Lake Okeechobee could harm the newly grown submerged aquatic vegetation. Nature intended the water to sheetflow slowly into the lake from the north. Thanks to flood control measures, canals now send the water quickly into the big lake. The backflow from the C-44 Canal contributes to that flow.
With the lake now rapidly rising, the corps has stopped flow at Port Mayaca, although boat traffic through the lock continues. For the most recently seven-day period, the backflow at Port Mayaca averaged 91 cubic feet per second, down from an average over 300 cfs the previous week.
With the report of an algae bloom starting in the C-44 Canal, coastal residents do not want the water released into the St. Lucie River.
Heavy rainfall is predicted to continue, as Floridians watch tropical storms approach the peninsula.
What’s the best solution for dealing with the C-44 water?
Dr. Paul Gray of Audubon Florida offered an idea: Pump the water and the algae from the C-44 Canal into the reservoir at Caulkins Water Farm.
Because of the soil composition and the hydrology of the area, water pumped onto the water farm percolates into the earth.
If there is blue green algae in the water, it would be broken up by the action of pumps that draw water onto the shallow reservoir on the former citrus grove, then the plants that grow in the water there would compete with the algae for nutrients.
The problem: The existing plan with the South Florida Water Management District and the U.S. Army Corps of Engineers has restrictions that limit the use of the water farm. The water farm can’t pump water into the shallow reservoir on the former orange grove unless authorized by SFWMD and the corps. Certain conditions are required to trigger that authorization.
It would make a lot of sense, explained Dr. Gray, for water managers to make that contract more flexible.
Caulkins Water Farm
Caulkins Citrus Co., once home to orange groves, is the site of a public-private partnership to reduce harmful freshwater flows to the St. Lucie Estuary.
The 3,200-acre site is adjacent to the C-44 Canal just east of Indiantown. Water from the canal is pumped into bermed reservoirs on the property, where it stays until it evaporates or percolates through the earth into the aquifer. As the water level on the water farm drops naturally, more water can be pumped onto the property.
About 2,800 acres can hold water up to 4 feet deep.
The property is divided into cells with interconnecting pipes to move the water between the cells. The smaller cells are safer than one large reservoir because they reduce the potential pressure on the berms from storm surges. Thick mats of aquatic vegetation cover much of the water surface, helping to clean and purify the water.
George Caulkins said back in February and March, when the corps decided to open the Port Mayaca Lock in an attempt to lower the lake level during the dry season, they pumped about 8,000 acre-feet of water onto the water farm, preventing that additional freshwater flow from going through the St. Lucie Lock into the estuaries.
Since March, the pumps have stayed off most of the time. In July, when water managers sought to lower the level of the C-44 Canal in anticipation of a heavy rainstorm, they pumped about 4,500 acre-feet of water out of the C-44 Canal. At that same time, water from the C-44 Canal also backflowed into Lake Okeechobee.
With the lake rising, the corps has stopped the backflow at Port Mayaca. Mr. Caulkins said they would like to turn the pumps on to help prevent nutrient-rich freshwater flow (which could contain algae) from flowing into the St. Lucie estuaries.
“We’d love it if they sent it to us,” he said. “It’s what we do. Once it comes to us, none of the bad stuff goes anywhere. We try to be as helpful as we can.”
The current protocols for use of the water farm limit what they can do. Caulkins Water Farm cannot turn on the pumps without permission from the district. The district also tells them when to turn the pumps off. He said they usually turn off the pumps when the water farm’s reservoir is within an inch or two of capacity.
Mr. Caulkins said he would like to come up with a protocol that would allow the water farm to take in water from the C-44 and, under certain conditions, release clean water back to the C-44, using the farm for some storage and treatment instead of just for water disposal.
“If they let us release water, it is always going to be cleaner than what we pump in,” he said. The vegetation within the water catchment area naturally removes nutrients from the water.