OKEECHOBEE — How much additional storage would it take to prevent harmful freshwater flows from Lake Okeechobee to the coastal estuaries?
Let’s do the math.
During the 2018-2019 dry season, when the corps was actively trying to lower the lake in order to allow the submerged aquatic vegetation (SAV) to recover from the damage left by Hurricane Irma, the extra dry season flow released was about one foot on Lake Okeechobee. (This amount was in addition to the freshwater releases already in the schedule to prevent salt water intrusion in the Caloosahatchee River.)
It’s a big lake. That’s a lot of water. One inch on the lake is about 12 billion gallons. So, that’s 144 billion gallons of water or 514,248 acre feet.
The UF Water Institute study called for about one million additional acre feet north and south of the lake, taking the history into account, not just the most recent years. Average rainfall years are not the problem in terms of water storage. The storage is needed to manage flood years and drought years.
Could the ASR storage in LOWRP tip the balance and prevent the need to release freshwater east and west?
The storage in the C-44 reservoir is primarily for local basin runoff from the Caloosahatchee Basin. It can take additional lake water if there is capacity, but in a heavy rainfall year it is likely to be filled with local basin runoff. The same goes for the C-43 and the St. Lucie watershed.
South of the lake, the EAA reservoir is anticipated to provide 240,000 acre feet of storage, but in the wet season some of that capacity will be filled with direct rainfall and local basin runoff. For example, in June 2017, so much rain fell south of the lake water managers backpumped billions of gallons water from the south of the lake into Lake Okeechobee to protect the wildlife in the Everglades. At the time FWC officials reported the wildlife could no longer find refuge from the rising water on the Everglades tree islands, because the islands were under water. Had the EAA reservoir been in place, that water would have gone into the reservoir. So not all of the 240,000 acre feet capacity can be used to store excess lake water.
Lake Okeechobee Watershed Restoration Plan (LOWRP) includes 448,000 acre feet of storage per year via aquifer storage and recovery (ASR) wells and about 43,000 acre feet of storage in a large, shallow reservoir.
Lake area residents have opposed the shallow reservoir on the grounds that they believe it simply will not store water as water moves through the earth there. They have seen water in impoundments rise and fall with the lake level. But even without the shallow reservoir, the corps estimates 448,000 acre feet of storage could be achieved with ASR wells. Combined with the other CERP projects already in progress, it could significantly reduce harmful discharges to coastal estuaries.