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LOSOM Optimized Model

The Optimized Model is expected to guide LOSOM drafting that will govern Okeechobee releases for years to come.
LOSOM Optimized Model
Cover page of the Army Corp's slideshow presentation on November 16, 2021.¹ 

For historical context on the importance of the Lake Okeechobee System Operating Manual ("LOSOM"), click here.

The Army Corp of Engineers ("Army Corp") released details on its optimized model run (the "Optimized Model") on November 16, 2021, which is expected to guide substantive drafting of LOSOM and related documents.2 LOSOM and related documents will likely govern freshwater releases from Lake Okeechobee (the "Lake") for the coming decade.

Substantive LOSOM drafting will be based on this Optimized Model, which is near finalized.3

The Optimized Model is noticeably different than pre-optimized Plan CC (to read about pre-optimized Plan CC and other context, click here).

The vertical axis shows the water level of the Lake, measured at a listed lock and dam in the Caloosahatchee and St. Lucie Rivers respectively. The relevant locks and dams are listed in the outside columns of arrows, which show allowable flows to the respective river, depending on the water level and time of year, shown on the horizontal axis. Each Zone is comprised of the area between its label and the line above it (except Zone A does not have an upper limit). In sum, the Zones demonstrate a range of releases allowable to the estuaries depending on water levels of the rivers’ locks and dams and the time of year. The pink arrow demonstrates releases south could occur when the Lake level is above roughly 11.5 feet. The chart also notes that when Lake levels fall into the Water Shortage Management Band (ranging from 10.5-13 feet),4 releases are determined by the State of Florida, and that when water levels are extremely high (roughly 17 feet), maximum releases are allowable.

The most prominent improvement in the Optimized Model from pre-optimization Plan CC is to Zone D, where the Lake is expected to sit about 76% of the time.5 Up to roughly 17 feet, the Final Model does not allow more than 2,000 cubic feet per second of releases to the Caloosahatchee and allows none to the St. Lucie. Zone F from the pre-optimized Plan was also removed, facilitating low volume beneficial releases to the Caloosahatchee. Flows south to the Everglades are also authorized at significantly lower Lake levels than in pre-optimization Plan CC. These are major successes.

Note, however, that the Optimized Model allows high and even unlimited volume flows when the Lake level is high enough in Zones A-C and is not much of a change from the pre-optimized Plan CC in this regard. The Lake is expected to be in Zones A-C roughly 4.7% of the time, during which these high volume releases are allowed.6 However, these expectations are mere estimates and also do not consider the quantity of times the Lake level enters into a particular Zone.7

There seems to be a misunderstanding among media outlets that harmful discharges were reduced by a certain percentage in the Optimized Model. The Optimized Model does guarantee a set percentage of freshwater releases, though it seems that it will result in a substantial reduction.

Conditions are also expected to worsen as to Lake Okeechobee's ecology.8 The Army Corp has indicated on many occasions that any improvement requires a tradeoff. This is not a satisfying justification and does not sound very creative. Land acquisition, restoration projects, and local government laws are a few examples of other factors that may play a role in the Lake's ecology and restoration generally. Understandably, the Army Corp's comments are based off of its limited scope in modeling tradeoffs between stakeholders while it develops LOSOM. It Is important to note that the Army Corp's modeling is only one factor affecting Everglades and coastal restoration and ecology.

There also seems to be a misunderstanding among media outlets that the LOSOM process is over.

The Army Corp actually indicated during its presentation that it still needs to "merge [the] selected model run with all of the other feedback and lessons learned."9 As such, the Optimized Model may not be the final model, though it seems close. Once this vague merging is done, substantive drafting will begin on the actual Lake Regulation Schedule, Water Control Plan, and Environmental Impact Statement.10

In other words, the drafting of the language behind LOSOM and documents that must be approved to implement it have not begun. Scientific and mathematical modeling have been done, and estimations made. However, the Record of Decision marking the conclusion of the LOSOM process is not projected to be approved until 2023 after the above mentioned documents are revised and commented on extensively.11 As such, no one has the ability to tell what percentage of discharges will be reduced in the coming years, because that depends on what Zone the Lake will be at years down the road. There are also no guarantees the Optimized Model will not change.

So, LOSOM is not and should not be considered finalized until the necessary drafting is completed. The Optimized Model sounds promising, but the LOSOM process is not over, and this is not a time for complacency.

Having said all of that, the Optimized Model seems like a major improvement over the pre-optimized Plan CC and existing Lake Okeechobee Regulation Schedule from 2008. It should be supported as such. GHL commends the Army Corp, SFWMD, and other stakeholders for their diligent effort in getting to this point.

The final slide In the Army Corp's November 16, 2021 slideshow presentation.12

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Table of Citations

1-3Lake Okeechobee System Operating Manual (LOSOM), U.S. Army Corp of Engineers (Nov. 16 2021)

4Central and Southern Florida Project: Water Control Plan for Lake Okeechobee and Everglades Agricultural Area, U.S. Army Corp of Engineers (2008).

5-12Lake Okeechobee System Operating Manual (LOSOM), supra.