Lake Okeechobee Geology

Lake Okeechobee is a massive, but shallow, freshwater body of water in south-central Florida. It covers 730 sq mi (1,900 sq. km) which is approximately half the size of the state of Rhode Island. It is the largest body of fresh water entirely within the United States. 1 However, its median depth is only 6 feet (2 m.) Its maximum depth is 13 feet (4 m.) Many areas of the lake near the shore are less than knee deep.

Much of the lake is less than six feet (2 meters) deep. 2 The Everglades are essentially a section of the original lake, which over time has filled with sediment and vegetation. The lake is fed by springs and small rivers flowing out of an aquifer originating in northern Florida. Its primary outlet is the Caloosahatchee River, which flows to the Gulf of Mexico.

Okeechobee is the Anglicization of the Itsate Creek (Miccosukee) words Oka chopi, which mean “Water Big.” 3 Its aboriginal inhabitants called the lake either Maya-imi, which apparently means “Maya Water or Mayakaa, which means Maya People in several northern South American tongues. 4 The Spanish called it Laguna de Mayaco or on some maps Laguna de Espiritu Santo. However, that name more typically applied to the Apalachicola-Chattahoochee River. In 1821, when Florida was ceded to the United States, the earliest English language maps generally retained the Mayaco name, but some called it Macaco.

A shallow geological trough underlies Lake Okeechobee, the Kissimmee River Valley and the Everglades. Compacted clay is located underneath the water, but over Eocene limestone strata. 5 The trough was dry land until about 6,000 years ago. The Atlantic Ocean continued rising because of the melting glaciers. Florida’ water table rose commensurately.

From 6,000 to 4,000 years ago, wetlands formed and started building up peat deposits. 6 The wetlands were eventually drowned by water flowing into the trough. A consistent trait of Lake Okeechobee during the eons was that it would expand and contract in response to swings in the region’s climate.

Along what is now the southern edge of Lake Okeechobee, the wetlands built up the layers of peat rapidly enough to form a dam, until the lake overflowed into the Everglades. Because of this natural dam, the lake holds 1 trillion gallons of water and is the main source of water for the Everglades.

The center of Lake Okeechobee is approximately 87 miles northwest of Downtown Miami. The center of the Lake is 128 miles southeast of the mouth of Tampa Bay and 522 miles southeast of Atlanta, GA. The eastern edge is only 26 miles from the Atlantic Ocean. The western edge is 60 miles from the shore of Charlotte Harbor. 7

During wet weather, Lake Okeechobee was considerably larger and slightly deeper prior to the mid-1800s. As soon as the Seminoles and Miccosukee were driven either to the Indian Territory or to Florida reserves, engineers began constructing canals to drain the swampy areas of Florida. These canals proved ineffective during a series of catastrophic hurricanes in the 1920s that killed several thousand people around Lake Okeechobee. Most of the deaths were caused by the tidal surges of the hurricanes. Water sufficiently deep to drown humans and livestock was swept on to normally dry land.

The US Army Corps of Engineers afterward began constructing a network of large drainage canals, most notably the Okeechobee and Caloosahatchee Canals to quickly drain off surges. 8 The COA also built a dyke around the lake to help hold back floodwaters. They were later expanded and improved. The most recent severe hurricanes in South Florida did not cause significant casualties near Lake Okeechobee.

Canals are still draining that section of Florida, but are being more closely regulated by the US Army Corps of Engineers and State of Florida to insure that the region is not drained excessively. In the late 20^th century, it was discovered that excessive drainage was damaging the ecological health of the Everglades. The COA now seeks to maintain a fine balance between human safety and the health of South Florida’s ecology. The effort requires constant adjustments as more is learned about nature.

Citations:

1. Article on Lake Okeechobee, Wikipedia.[↩]
2. Article on Lake Okeechobee, Floripedia[↩]
3. Author is of Itsate (Hitchiti) Creek heritage like the Miccosukee.  Most references state that the word for “big” in Itsate is Chobe, but there is no “b” in the Creek alphabet.[↩]
4. Floripedia.[↩]
5. Everglades Forever.  Web site sponsored by the State of Florida.[↩]
6. Everglades Forever.  Web site sponsored by the State of Florida.[↩]
7. Calculations by author using ERSI GIS software.[↩]
8. Everglades Forever.  Web site sponsored by the State of Florida.[↩]