Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida

Why Releases from Lake O Would Cause Harm Now

September 30, 2020

By Chad Gillis

Consistent with recommendations in SCCF’s weekly Caloosahatchee & Estuary Condition Report, the U.S. Army Corps of Engineers (USACE) last week held off on releasing water from Lake Okeechobee, with the surface of the lake approaching 15 and a half feet above sea level. 

Under the current Lake Regulation Schedule, the Army Corps tries to maintain the lake between 12.5 and 15.5 feet to maintain a healthy lake ecology, provide flood protection, and water supply to agriculture, urbanized areas, and natural systems like the Caloosahatchee and its estuary. 

The surface of the lake is currently at 15.52 above sea level, according to the Army Corps.

Excess water is already flowing off the Caloosahatchee River watershed, the lands and creeks, and streams that flow into the river and estuary. 

Flows measured at the W.P. Franklin Lock and Dam have been above the harmful threshold for weeks now and for the past week flows averaged more than 3,080 cubic feet per second, according to Army Corps data. 

 Flows at this level fall within the ecological “harmful threshold” identified by scientists and water managers, the point at which damage starts to occur in the estuary. 

The lock is the eastern edge of the brackish estuary, which extends west to Sanibel and Captiva Islands. Water released from Lake Okeechobee at this point in the 2020 rainy season would compound the impacts of stormwater runoff from the Caloosahatchee watershed. 

Not only would the extra freshwater flows further disrupt salinity conditions in the estuary, but releases could also deliver nutrients that can fuel harmful algal blooms within the estuary or along the Southwest Florida coast.

Barring any major storm or hurricane, Lake Okeechobee may soon stop rising as the rainy season typically ends in mid-October. Looking at water levels now and how much time is left in the rainy season, there may be just enough room left in Lake Okeechobee to make it through the next three weeks without releasing water to the estuaries. 

That would certainly be a good thing for our river, estuary, and islands. 

Blue-green algae blooms, which have the potential to produce toxins harmful to human health, are common on Lake Okeechobee during the warmer summer months.

A particularly nasty bloom exploded in Lake Okeechobee in 2018 after heavy rains in May of that year. Water was released down the Caloosahatchee River during the bloom and toxic blue-green algae showed up soon after in the estuary.

The blue-green outbreak came at a particularly bad time as there was already a red tide event occurring in the Gulf of Mexico. Coastal Lee County was at the heart of both the blue-green algae and red tide outbreaks, and the two combined crippled the local fishing, tourism, and real estate economies. 

The Army Corps has taken a different approach in recent years, releasing water down the river during the dry season to help manage lake levels instead of waiting until the rainy summer months.

The Corps’ action has resulted in additional storage capacity within the lake to absorb incoming freshwater flows and minimize the need for freshwater flows to the estuaries.

The idea was to lower levels before the rains started so that the Army Corps wouldn’t have to conduct releases when there was a blue-green algae bloom on the lake.

And it worked, for the river and estuary as well as Okeechobee itself. The lower levels actually helped the ecology of the lake. Thousands of acres of aquatic plants that were destroyed by Hurricane Irma in 2017 regrew and that vegetation acts as a water filter as well as wildlife habitat.

Allowing the surface of the lake to fall below 12 feet above sea level was good for the health of the lake, and it was good for the Caloosahatchee River and its estuary.

Agriculture interests want to see the lake higher later into the year to ensure there will be enough water for irrigation.

Representatives from the Florida Farm Bureau Federation said last week at a Florida Department of Transportation meeting that they want the lake kept above 12.5 feet, which has been the standard operating procedure for more than a decade.

Allowing the lake to occasionally fall below 12.5 feet, however, is good for the health of the lake and the estuaries.

Here, on the Southwest Florida coast, we should advocate for lower lake levels during the end of the dry season with the lake level building throughout the rain season to approximately 15 feet above sea level.

That scenario helps ensure there’s enough water the Caloosahatchee ecosystems during the following dry season and minimizes conditions for the development of blue-green algae blooms in the lake.

As we transition from rainy season to dry season hopefully those conditions will allow the Army Corps to continue to hold off on releases.

The Army Corps will make its decision later this week on whether or not to release water to the estuaries. 

Video Credit: Nick Adams Photography, Friday, Sept. 18.


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