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LOSOM Pre-Optimized Plan CC

Plan CC has since been optimized but this information remains useful in understanding the work being done by the Army Corp.
LOSOM Pre-Optimized Plan CC

For history contextualizing the importance of the Lake Okeechobee System Operating Manual ("LOSOM"), click here. The LOSOM process leading up to November 16, 2021 is set forth below, mainly centering on the initial preferred alternative model selected by the Army Corp of Engineers ("Army Corp") on August 9, 2021. This model has since been optimized (click here to read about LOSOM post-optimization) but the information remains useful for understanding the work being done by the Army Corp and where LOSOM stands currently.

The Army Corp is  developing LOSOM, in part to account for progress made under Comprehensive Everglades Restoration Plan ("CERP") plans and infrastructure improvements (click here to read about an example of a CERP plan, the EAA Reservoir, though LOSOM will have to be revised to account for the EAA Reservoir specifically, as it will not be complete for about two years).1 LOSOM will determine what specific schedule the Army Corp follows in determining when, to where, and roughly how much water flows from Lake O.2 Unpredictable factors such as hurricanes require a level of flexibility, but LOSOM will contain guidelines with optimal ranges of seasonal water flows.3 The conceptual goal of LOSOM is to create a more balanced water management plan for all stakeholders.4

LOSOM has been in development since early 2019, with many public meetings and opportunities to provide feedback.5 Substantive work began with the development of conceptual plans, in which the Army Corp “simulat[ed] ~120,000 variations of conceptual schedules using a subset of sensitive and representative criteria to guide the analysis.”6 During “Iteration 1” of the process, eight single-objective plans were developed, in which models focused specifically on algal bloom risk, navigation, recreation, water supply, and the ecology of the major individual water bodies.7 The goal of Iteration 1 was not to pick a plan, but to see what worked.8

Next, during Iteration 2, elements of the single-objective plans were combined, modified and narrowed down to six, more balanced, plans (AA, BB, CC, DD, EE1 and EE2) that varied in performance across different metrics.9 These plans were scored against a no-change alternative based on their impact on Lake Okeechobee, navigation, recreation, ecology of both the St. Lucie and Caloosahatchee estuaries, algal bloom risk in both the St. Lucie and Caloosahatchee estuaries, south Florida ecology generally, and water supply for each of the Seminole Tribe of Florida, Lake Okeechobee Service Area, and Lower East Coast Service Area.10

Among conservation non-profit organizations, the general consensus was in support of Plan CC, subject to revision and optimization during Iteration 3.11 However, the consensus was also that Plan CC was unacceptably harmful to the Caloosahatchee’s ecology.12

As part of Iteration 2, the Army Corp selected Plan CC as its starting point and conducted a roadshow designed to hear feedback as to how various stakeholders wanted to see Plan CC optimized, or revised, during Iteration 3.13 The chart below,14 showing Plan CC pre-optimization, has since been optimized to address follow up stakeholder concerns and comments.  

Modeling for Plan CC prior to optimization (pre-November 16, 2021)15

The vertical axis shows the water level, measured at a listed lock and dam in each respective river. The relevant locks and dams are listed in the outside columns of arrows, which show allowable flows to each river, depending on water level and the time of year, shown on the horizontal axis. Each Zone is comprised of the area between its respective line and the line for the Zone 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 13 feet. The chart also notes that when Lake levels fall into the Water Shortage Management Band (ranging from 10.5-13 feet),16 releases are determined by the State of Florida, and that when water levels are extremely high (roughly 17 feet), maximum releases are allowable.

Flows to the Caloosahatchee are measured at two different locks, the S-77 Moore Haven Lock by the Lake and the S-79 Franklin Lock by the estuary. On the other hand, as seen above, flows to the St. Lucie are measured only at the S-80 lock by its estuary. Naturally, measurements of water level at the estuary factor in watershed runoff from upstream, while measurements by the Lake upstream do not. As such, by measuring the water level near the Lake, Plan CC under-represents how much water the Caloosahatchee estuary is authorized to receive.

Stakeholders raised issues with pre-optimized Plan CC, mainly centering on the high volume of allowable flows, measured in cubic feet per second (“cfs”), to the Caloosahatchee.17 Stakeholders advocated for flows within the Optimal Flow Envelope (which was 750–2100 cfs in 2020), especially in Zone D, likely to be the most prominent zone,18 and also in Zones B and C, which allowed for releases up to 7,200 cfs. Stakeholders also called to remove Zone F, allowing more beneficial dry season releases to the Caloosahatchee19 and to consider and improve upon modeling done by SFWMD.20

On November 16, the Army Corp released the optimized model run (the "Optimized Model")21 on which the substantive drafting of the LOSOM Lake Regulation Schedule, Water Control Plan, and Environmental Impact Statement will be based:

Substantive LOSOM drafting will be based on this near finalized Optimized Model.22

Click here to read more about the Optimized Model.

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Table of Citations:

1EAA Water Reservation FAQ, South Florida Water Management District (2020).

2-3Lake Okeechobee System Operating Manual (LOSOM), a Component of the Central & Southern Florida (C&SF) System Operating Plan, U.S. Army Corp of Engineers (2021).

4Lake Okeechobee System Operating Manual, Leslye Waugh, South Florida Water Mangement District (April 8, 2021).

5Lake Okeechobee System Operating Manual (LOSOM), a Component of the Central & Southern Florida (C&SF) System Operating Plan, supra.

6Lake Okeechobee System Operating Manual (LOSOM) Preferred Alternative, U.S. Army Corp of Engineers (August 9, 2021).

7-8Lake Okeechobee System Operating Manual, supra.

9-10Lake Okeechobee System Operating Manual (LOSOM) Preliminary Preferred Alternative, U.S. Army Corp of Engineers, (July 19, 2021) (see page 8).

11LOSOM Update: Army Corps Selects Preferred Alternative, The Everglades Foundation (2021); Leaders Unite to Call on Corps to Send Water South, Sanibel-Captiva Conservation Foundation (2021).

12Tell The U.S. Army Corps LOSOM Must Be Balanced For All Stakeholders, The Conservancy of Southwest Florida (2021); Leaders Unite to Call on Corps to Send Water South, Sanibel-Captiva Conservation Foundation (2021).

13-16 Lake Okeechobee System Operating Manual (LOSOM) Preferred Alternative, supra.; Central and Southern Florida Project: Water Control Plan for Lake Okeechobee and Everglades Agricultural Area, U.S. Army Corp of Engineers (2008). Lake Okeechobee System Operating Manual (LOSOM), a Component of the Central & Southern Florida (C&SF) System Operating Plan, supra; Lake Okeechobee System Operating Manual (LOSOM) Preliminary Preferred Alternative, supra.

17Tell The U.S. Army Corps LOSOM Must Be Balanced For All Stakeholders, The Conservancy of Southwest Florida (2021); Leaders Unite to Call on Corps to Send Water South, Sanibel-Captiva Conservation Foundation (2021); Letter from Byron Donalds to Colonel Andrew Kelly (August 3, 2021); LOSOM Update: Army Corps Selects Preferred Alternative, The Everglades Foundation (2021).

18RECOVER Northern Estuaries Performance Measure: Salinity Envelope, U.S. Army Corp of Engineers (2020).

19-20Lake Okeechobee System Operating Manual (LOSOM) Preferred Alternative, supra.

21-22Lake Okeechobee System Operating Manual (LOSOM), U.S. Army Corp of Engineers (Nov. 16 2021)