Flow under the Tamiami Trail to Everglades National Park continued at around 2,200 cubic feet per second (cfs) the week of Sept. 16-22, according to information shared by Col. James Booth, commander of the U.S. Army Corps of Engineers (USACE) Jacksonville District during a Sept.  22 media briefing.

Since the start of the year, about Almost 917,000 acre feet of water has flowed Water Conservation Area (WCA-3A) into the park.  That's close to the equivalent to 2 feet of water on Lake Okeechobee.

Where did that water come from?

Flow into the park comes through Water Conservation Area 3-A under the Tamiami Trail. Flow into the WCA-3A is complicated.

Some of the water in WCA-3A is direct rainfall into WCA-3A. Some comes from the other WCAs.

Some of the water in the other WCAs comes from direct rainfall into those WCAs. Some comes from flow from the Everglades Agricultural Area (EAA) stormwater treatment areas (STAs).

Some of the water in the EAA STAs comes from direct rainfall into the STAs. Some comes from runoff from the EAA. Some flow comes via canal from Lake Okeechobee.

During the wet season, EAA farms are primarily watered via rainfall. When there is not sufficient rainfall, the farms are irrigated with water from Lake Okeechobee.

Some of the water in Lake Okeechobee comes from direct rainfall. Some comes from flow into the lake from the Kissimmee River, Fisheating Creek and Taylor Creek/Nubbin Slough. When the lake level is below 14 feet above sea level,  water may backflow into the lake from the C-44 canal at  Port Mayaca.

According to the South Florida Water Management District data, from May 1 to Sept. 4, Lake Okeechobee inflows totalled 747,800 acre feet and outflows totalled 160,200 acre feet of water.

While USACE tracks the volume of water flowing under the Tamiami Trail into Everglades National Park,  “it’s hard to tell you which drops of water those are at that point,” said Booth.

Water in the lake, the STAs and the WCAs also evaporates into the air, percolates into the aquifer and is used in plant transpiration.

According to information shared at the September meeting of the South Florida Water Management District (SFWMD)  Governing Board, from May 1, 2023 to Sept. 4, 2023, flow from the EAA STAs into the WCAs was about 642,500 acre feet. 

During that same period, flow south from Lake Okeechobee was 32,100 acre feet. During the wet season, the EAA STAs are usually full from direct rainfall and local basin runoff. They were built and designed to clean the water from the EAA, not to clean water from Lake Okeechobee. The EAA farmers pay a special tax per acre, which generates about $11 million a year to help with costs of maintaining the STAs.

The EAA reservoir and STA, currently under construction, will be designed to take water directly from Lake Okeechobee via the canals which cut through the EAA.  The reservoir completion date is estimated as 2030. Even before the reservoir is complete, the new STA will accept and treat water directly from Lake O.

USACE is currently making improvements to the Miami Canal and the North New River Canal to increase capacity to flow water out of Lake O to the EAA reservoir and STA.

(SFWMD has taken the lead on construction of the STA. The STA is expected to be completed in 2024 and should be able to accept and treat some water from the big lake before the EAA reservoir is finished. The initial vegetation planting in the STA is planned for this fall.

Before water can be released into Everglades National Park, it must meet treatment standards for phosphorus content. Too much phosphorus disrupts the balance of the natural ecology of the park because it encourages the overgrowth of plants like cattails which may push out other plants that require less phosphorus.

After the reservoir is complete, water will flow from the lake into the reservoir and then into the STA for treatment before flowing south under the Tamiami Trail to Everglades National Park.  As with the rest of the system, some of the water in the reservoir will come from direct rainfall.