U.S. Army Corps of Engineers officials often remind the public that “most of the time, Mother Nature is in charge.” That has certainly been the case this summer, with sporadic rainfall unable to compensate for the searing summer heat. The heat and the unusual weather patterns mean a lot of water is moving into the air via evapotranspiration (a combination of evaporation and plant transpiration).
During what should be the “wet season” when the lake level should be rising, it is instead falling. The inflows have not kept up with water lost.
According to the SFWMD environmental conditions report issued Aug. 24, total lake releases to the Flow Equalization Basin (FEBs) and Stormwater Treatment Areas (STAs) in WY 2023 (which started May 1) inflows to the STAs were approximately 420,000 cubic feet including lake releases of 12,400 acre feet.
That means approximately 407,000 acres began as rain that fell on the Everglades Agricultural Area flowed into the STAs, which clean the water and feed flow into the Water Conservation Areas. Without the flow from the EAA, the STAs would have been very dry this year.
For that same period, according to the U.S. Army Corps of Engineers, approximately 267,136 acre feet of water was delivered across Tamiami Trail to Everglades National Park. That flow include water from the STAs that flowed into the WCAs as well as direct rainfall into the WCAs.
So what happened to the rest of the water? If water continues to flow into the STAs and WCAs as well as fall as direct rainfall into the WCAs, where is it going?
Most of the water that leaves the WCAs goes into the atmosphere via evapotranspiration.
For example, for the week of Aug. 15 to Aug. 21, WCA 2A and 3A received direct rainfall of 28,280 acre feet of water and inflows of 6,720 acre feet. For that same period, WCA 3A lost 61,350 acre feet of water to evapotranspiration. That’s about 17 billion gallons of water lost to evapotranspiration (the equivalent of 1.4 inches on Lake Okeechobee).
That same week, Lake Okeechobee received direct rainfall of 13,310 acre feet of water and inflows of 3,430 acre feet, but lost 31,530 acre feet of water to evapotranspiration. That’s about 8.8 billion gallons of water lost to evapotranspiration (the equivalent of 0.73 inches on Lake O).