Direct rainfall into Lake Okeechobee was sufficient to raise the lake level more than 6 inches according to data from the South Florida Water Management District.

According to the SFWMD Weekly Water Level Report for June 10-16, heavy rains that week contributed 239,760 acre feet of water. One acre foot is the amount of water to fill one acre of land with water 1 foot deep.

That same period, rainfall north of the lake was not as heavy. Surface inflows from the north accounted for 58,230 acre feet of water.

Outflows for the week were just 4,150 acre feet west to the Caloosahatchee River. Most of the week, no lake water was released as there was heavy rainfall in the basin.  During and following the storms, flow at the W.P. Franklin Lock averaged 13,000 cubic feet per second (cfs) with no flow from Lake O.

Lake O water is only released to the Caloosahatchee River when local basin runoff fails to meet the 2,000 cubic foot per second (cfs) flow target, measured at the W.P. Franklin Lock, which is more than 43 miles from Moore Haven, where the lake water enters the river. When there is little local basin runoff, the river needs freshwater flow from the lake to maintain optimal salinity levels in the estuary.

During that same seven-day period, water from the St. Lucie Canal (C-44 canal) backflowed into Lake Okeechobee. Most of the excess local basin runoff in that basin was pumped into the C-44 reservoir, but the rain came down so quickly they could not pump it fast enough to keep the canal level in check, Col. James Booth, commander of the U.S. Army Corps of Engineers (USACE) Jacksonville District, explained in a June 14 media briefing. Instead of releasing the excess water through the St. Lucie Lock into the St. Lucie River, USACE opted to prioritize the health of the St. Lucie estuary and allowed the excess water to backflow into Lake Okeechobee.

USACE tries to keep the St. Lucie Canal at 14 to 14.5 feet above sea level for navigation and water supply. When Lake O is below 14 feet, water can backflow through the water control structure at Port Mayaca.

Evapotranspiration (a combination of evaporation and plant transpiration) removed 22,030 acre feet of water from Lake O.

No lake water flowed south during that period, as heavy rainfall south of the lake flooded the Everglades Agricultural Area (EAA), the stormwater treatment areas and the water conservation areas (WCAs) south of the lake. Between June 12 and June 15, EAA farms received nearly 15 inches of rainfall. The flood control system provides drainage of just ¾ inch of water per day for the EAA.

WCA 2A and WCA 3A received 504,850 acre feet of direct rainfall – the equivalent of more than 1 foot of water on Lake Okeechobee. Flows south under the Tamiami Trail totaled 13,600 acre feet.

On June 10, Lake Okeechobee hit the lowest lake level for the year at 12.63 feet. On June 16, the lake level was 13.39 feet.

Booth said the federal flood control system performed as intended after the recent rain storms. He said flooding in the urban areas was due to lack of capacity in the smaller canals that fall under the jurisdiction of cities and counties. “They don’t have the capacity to handle more than a foot of rain in just a few hours,” he explained.