Lake suffering from lack of rainfall

WEST PALM BEACH — Water Year 2020, which started on May 1, 2019 ,and runs through April 30, 2020, has set records twice, with the driest September on record and the driest March in 89 years.

Lake Okeechobee News/Richard Marion
OKEECHOBEE – This photo, taken April 13 at the Clif Betts Memorial Lakeside Recreation Area (aka Lock 7) on the lake’s north-ern shore, shows the level of Lake Okeechobee receding, allowing bright green vegetation to grow under the pier. The trees show the normal high water mark.

Most of the South Florida Water Management District (SFWMD) is in moderate drought, according to the water conditions report given by John Mitnik at the April 9 SFWMD governing board meeting.

He said the month of March was described as “exceptional long-lived unprecedented dryness.

“By the end of month we set a record for the driest March on record in the last 89 years,” he explained, with less than 30 percent of average rainfall throughout the entire district. Less than one-fourth of an inch of rain fell on the district.

Mr. Mitnik said the largest rainfall deficits are in Water Conservation Area (WCA) 3A and Everglades National Park.

He said the increased recession rate of Lake Okeechobee was associated with the lack of rainfall in month of March combined with the higher rates of evapotranspiration (ET) due to the hot, sunny days. For example, he said, according to the U.S. Army Corps of Engineers data, on one hot, cloudless day in March the loss of water by ET was the equivalent to an outflow of 7,000 cubic feet per second. Flow to the Caloosahatchee River is currently averaging a target of 457 cfs.

Another complication has come from the COVID-19 pandemic. Due to the pandemic, there have been fewer commercial airline flights.

“On average on any given day there are roughly 50,000 to 100,000 different data points the National Oceanic and Atmospheric Administration (NOAA) and National Weather Service (NWS) receive from commercial aircraft criss-crossing the country. With the decline in air travel there is less data flowing into the models the NWS uses to make predictions,” he explained. “The less data that you have, the performance of that model and reliability of that model takes a hit.”

Even with good data, predictions are just that, he warned. “Mother Nature doesn’t abide by these predictions, and she will do as she sees fit.”

South of the lake, the Water Conservation Areas (WCAs) are also suffering from a lack of rainfall.

If a WCA falls below its “floor,” no water can move south from the WCA unless an equal amount of water is flowing into the WCA from Lake Okeechobee.

He said WCA -1, which recharges the aquifer for Palm Beach County, has a floor of 14 feet and is currently just over 16 feet.

WCA 2 is already below its floor.

“WCA 3A, two days ago was just slightly above its regulatory floor,” Mr. Mitnik said. “Should WCA 3 cross below its floor, in order to move water to the lower east coast, we would have to start bringing in water from Lake Okeechobee prior to those types of operations.”

He said they want to keep the water as high in the system as possible because that provides the greatest flexibility to address rain deficits. They rely on gravity flow to move most of the water. Once water flows south, they can’t move it north again.

He said 96 percent of the public water supply in the district comes from groundwater. “The vast majority of utilities along lower east coast pull groundwater as their source of water.”

The lake and WCAs serve as the primary recharge for the aquifers. The water management district has a network of water monitoring wells. The monitoring sites show the water levels are in their average or slightly below average levels for this time of year, he said.

He said if the groundwater levels decline, it increases the chance of saltwater intrusion.

Lawrence Glenn, who provided the environmental conditions report for the governing board, said the system is “pretty much dried out.”

When Lake Okeechobee’s water level is below 12 feet (above sea level), approximately 80 percent or more of the lake’s marshes are dry, he explained.

This affects animals that use the marsh habitat.

Conditions are very good for submerged aquatic vegetation (SAV) growth, he said, which is good for the ecology of the lake. While it is beneficial to the SAV, the low water level will impact in a negative way other organisms that use that marsh, he said.

He said there has been an increase in foraging water birds from about 6,000 to 9,000 because as the marsh dries out, it concentrates prey in the drying pools.

Birds that were using areas outside of the marsh to forage are moving into the Lake O drying ponds to feed.

While the wading birds are foraging, they are not nesting, he added. He said there are only 250 nesting pairs of wading birds in lake marsh this year because the marsh is just too dry.

There are no snail kites nesting in the lake marshes, he continued. This year has brought the slowest start to snail kites since 2010.

“When it is very dry, birds are looking to maintain their energy for their own survival. They are not going to invest that into young,” Mr. Glenn said.

He said the lake has less potential for a cyanobacteria blooms this year.

He said there is some potential for a blue-green algae bloom on the east side of the lake. He said they took samples on April 6 and 8 and sent them to Florida Department of Environmental Regulation for testing.

Overall the bloom potential is looking low, he added. Algae is a normal part of the lake’s ecosystem, he said. It’s always there as it is in all lakes.

Mr. Glenn said the increase in SAV will help reduce algae blooms in the lake because the SAV competes for the same nutrients as the algae.

He said the algae on the east side of the lake might have been wind blown against that shore. Cyanobacteria has the ability to rise and fall in a water column, but is moved from one area on the lake to another by wind and wave action.

While no water from the lake has been released to the St. Lucie River, some water from the C-44 basin has backflowed into Lake Okeechobee. This is common when the lake falls below 12 feet. According to the University of Florida Water Institute study, the water from the C-44 basin is higher in phosphorus and nitrogen than is the lake water. During the public comment period, Nyla Pipes of One Florida Foundation pointed out that the nutrients in the backflow feed algae blooms on the east side of the lake.

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