U.S. Army Corps of Engineers begins pulse release from Lake Okeechobee to Caloosahatchee Estuary

JACKSONVILLE, Fla. – The U.S. Army Corps of Engineers, Jacksonville District, will begin a water pulse release from Lake Okeechobee to the Caloosahatchee Estuary at 7 a.m. Saturday, Feb. 13.

This pulse release is needed because the last release (flows ended Feb. 4) did not fully achieve the desired benefits to the estuary. That release did bring salinity levels in the upper Caloosahatchee Estuary closer to the desired target, but levels are still slightly above the target. The Corps anticipates this release will benefit the ecology of the upper Caloosahatchee Estuary by maintaining variability in desired salinity levels in that area.

The 14-day release has a target average flow over the period of 650 cubic feet per second (cfs) measured at the S-79 (W.P. Franklin Lock and Dam). This release schedule does not include releases to the St. Lucie Estuary through the S-80 structure. “A 14-day release is unique. We’ve designed the release to have two peaks of flow as opposed to the single peak we include in a seven or ten day release,” said Col. Al Pantano, Jacksonville District commander. “One of our concerns has been the ‘downtime’ between typical releases. Those periods of no-flow appear to undermine the gains we make during a release.”

The release will simulate the effect of two “back-to-back” short duration rainfall events. “We will take a close look at conditions and the effect of the first simulated rainfall event,” said Pantano. “We expect to see some improvement in salinity conditions in the Caloosahatchee River’s upper estuary. We’ll evaluate the success of the first flow and then determine the second flow curve depending on the conditions we see. It’s possible we could determine at that point that additional flows are not needed.”

Inflows to the lake and the lake water level have both continued to rise for the past several weeks. The near-term weather forecast predicts rain for several areas in the basin. Water managers are predicting that the lake level may enter the Low Sub-band in a matter of days.

“We will continue to monitor conditions closely, and we may modify our plan along the way to maintain a balance of benefits and adversity among all the interests,” Pantano said. “If we see significant rainfall and basin inflow upstream of S-79, we would rely on the natural rainfall event to provide the freshwater needed to lower salinity, not lake water. However, if we have significant inflows to the lake, and the lake level rises, we may have to increase flows to the estuaries. As always, we will coordinate closely with the South Florida Water Management District, and other agencies and interested parties.”

On Feb. 12, the lake stage (level) is 13.49 feet NGVD. The lake is within the Operational Band of the 2008 Lake Okeechobee Regulation Schedule (LORS). Specifically, the lake level is in the Base Flow Sub-band. In accordance with the LORS, releases may be made up to 450 cfs and 200 cfs to the Caloosahatchee and the St. Lucie estuaries, respectively. In addition, the regulation schedule allows these releases to be redistributed between the east and the west to minimize impacts and/or to provide additional benefits. Water managers will shift the 200 cfs allowance for the eastern outlet to the western outlet to achieve the environmental benefit 450 cfs is not likely to produce.

After the pulse release is complete, the Corps will reassess the conditions and coordinate closely with the South Florida Water Management District and other affected agencies, local governments and stakeholders regarding future actions.

A pulse-type release more closely resembles the naturally-occurring pattern of runoff into the estuary caused by rain, which normally leads to an increase in flow as rain continues to fall, followed by a gradual decrease as runoff comes to an end. Water managers expect these releases to help maintain salinity ranges that are conducive to the sustainability of estuarine organisms in the upper estuary. These releases also benefit the overall ecology of the area by promoting the mixing of salinity levels and nutrient concentrations from one water level to another.

For more information on water level data and flows for Lake Okeechobee and the Central and Southern Florida Project, visit the Corps’ water management page. Questions may be directed to Nanciann Regalado, 904.334.8954.