156B—Southern Florida Lowlands

This MLRA (shown in blue in the figure above) is entirely in Florida. It makes up about 1,835 square miles (4,750 square kilometers). It has no major cities or towns. It lies between Lake Okeechobee and the eastern coast. Interstate 95 parallels the eastern boundary of the area.

Physiography

This area is in the Floridian Section of the Coastal Plain Province of the Atlantic Plain. It is on nearly level lowlands. Agricultural canals drain this area. A few hummocks rise 3 to 6 feet (1 to 2 meters) above the general level of the landscape. Elevation is approximately 80 feet (25 meters).

The extent of the major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA is as follows: Southern Florida (0309), 56 percent, and St. Johns (0308), 44 percent.

Geology

This area is a young marine plain underlain by Tertiary-age rocks, including very fine grained shale, mudstone, limestone, and dolomite beds. A sandy marine deposit of Pleistocene age occurs at the surface in much of this area.

Climate

The average annual precipitation in this area is 46 to 60 inches (1,170 to 1,525 millimeters). About 60 percent of the precipitation occurs from June through September. Most of the rainfall occurs as moderate-intensity, tropical storms that produce large amounts of rain during the summer. Spring, fall, and winter are relatively dry. The average annual temperature is 71 to 74 degrees F (22 to 24 degrees C). The freeze-free period averages 360 days and ranges from 360 to 365 days.

Water

Following are the estimated withdrawals of freshwater by use in this MLRA:

Public supply—surface water, 0.2%; ground water, 5.6%
Livestock—surface water, 0.1%; ground water, 0.4%
Irrigation—surface water, 49.0%; ground water, 32.7%
Other—surface water, 2.8%; ground water, 9.3%

The total withdrawals average 305 million gallons per day (1,155 million liters per day). About 48 percent is from ground water sources, and 52 percent is from surface water sources. Rainfall and surface and ground water sources provide an abundance of water. The surface water is of good quality. Unless the water level in naturally wet areas is controlled, shallow water covers the surface during much of the rainy season. Canals and ditches control the ground water level for crops and pasture. Excess water is pumped out during the rainy season, and irrigation water is applied during the growing season.

Domestic water is obtained mainly from wells in a shallow, nonartesian aquifer. This aquifer provides limited quantities of water that is hard but of good quality. The water is dominantly a calcium bicarbonate type. High-capacity irrigation wells are usually drilled down to the artesian Floridan aquifer, which consists of deep limestone and dolomite beds. The water in this aquifer is a calcium bicarbonate type but has high amounts of total dissolved solids in this area. In some areas the artesian water is too salty for direct application on salt-sensitive citrus crops. The shallow aquifer is susceptible to contamination from surface activities.

Soils

The dominant soil orders in this MLRA are Alfisols, Entisols, and Histosols. The soils in the area dominantly have a hyperthermic soil temperature regime, an aquic soil moisture regime, and siliceous mineralogy. They generally are deep or very deep, poorly drained or very poorly drained, and loamy or sandy. Glossaqualfs (Pineda, Riviera, and Winder series), Endoaqualfs (Felda series), and Argiaquolls (Floridana series) formed in loamy marine sediments on flats and flood plains and in depressions. Psammaquents (Basinger series) formed in sandy marine sediments on flats and in depressions. Haplosaprists (Terra Ceia series) formed in organic deposits in marshes.

Biological Resources

This area supports “hummock and slough” swamp vegetation. Slash pine and cabbage palm are the dominant species. Saw palmetto, cordgrasses, and bluestems make up the understory.

Some of the major wildlife species in this area are white-tailed deer, feral hog, gray fox, raccoon, opossum, armadillo, rabbit, tree squirrel, wild turkey, bobwhite quail, mourning dove, Florida mallard, and woodpecker.

Land Use

Following are the various kinds of land use in this MLRA:

Cropland—private, 24%
Grassland—private, 37%
Forest—private, 6%
Urban development—private, 15%
Water—private, 4%
Other—private, 14%

Most of this area is in farms or ranches. Citrus fruits, the chief crops, are planted in beds between shallow ditches that are part of the water-control system. The vegetation on the rangeland in the area consists of native grasses, forbs, sedges, and a few scattered pines. The forestland in the area consists of mixed pine and cabbage palm or cabbage palm and hardwoods.

The major soil resource concerns are wind erosion, maintenance of the content of organic matter and productivity of the soils, and management of soil moisture. Conservation practices on cropland generally include conservation crop rotations, cover crops, nutrient management, pest management, water-control structures, surface drainage systems (field ditches, mains, and laterals), pumping plants, and irrigation water management (including microirrigation systems and surface and subsurface irrigation systems). Conservation practices on pasture and rangeland generally include prescribed grazing, brush management, pest management, prescribed burning, and watering facilities.

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