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Protecting Florida's Water Supply

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Learn About Your Watershed

Little Manatee River Watershed

  • Overview
  • Restoration News
  • Watershed Maps
  • Photos & Graphics
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Image of Little Manatee River winds through Hillsborough County to Tampa Bay.
Little Manatee River winds through Hillsborough County to Tampa Bay.

Watershed Stats

Size of Basin: 222 square miles

Counties: Manatee and Hillsborough Counties

Major Towns: Sun City, Ruskin, Palmetto, Parrish, and Wimauma

Major Water Features:
Little Manatee River, South Fork, North Fork, Lake Wimauma, Carlton Lake, and Lake Parrish

Overview

The Little Manatee River watershed extends from eastern Tampa Bay to the southeastern corner of Hillsborough County. Originating in a swampy area east of Fort Lonesome in southeastern Hillsborough County, it flows generally westward for about 32 miles towards its discharge point into Tampa Bay near Ruskin. At the headwaters, near Fort Lonesome, the river channel flows down a relatively steep gradient that eventually flattens out in the middle and lower reaches.

The Little Manatee River has 18 major tributaries. South Fork, located almost entirely in northeast Manatee County, is the largest, followed by North Fork. Both of these join the river about 22 miles above its mouth.

Image of Little Manatee River is designated as an Outstanding Florida Water.
Little Manatee River is designated as an Outstanding Florida Water.

The principal natural lakes in the watershed are Lake Wimauma and Carlton Lake. Lake Parrish is a man-made reservoir covering 6,000 acres, constructed just downstream from where the South Fork joins the Little Manatee River. The watershed also contains numerous intermittent, shallow ponds.

The watershed is largely undeveloped-particularly the eastern portion-compared with other areas draining to Tampa Bay. In 1995, urban development comprised about 10 percent of the watershed, while 63 percent was used for agriculture. In the western quarter, near the coast, urban development is prevalent in a north-south band and in areas near the major north-south transportation corridors (i.e., Interstate 75 and U.S. 301). Small urban areas such as Sun City, Ruskin, Palmetto, Parrish, and Wimauma are supported by local agriculture. Agricultural activities include citrus, dairy operations, row crops, and aquaculture.

In the eastern half of the watershed, the phosphate industry has large holdings that are either being mined or slated for mining in the near future. Areas of past, current, and future mining include the headwaters region of the Little Manatee River along the North Fork and the vicinity of the South Fork in Manatee County.

The rest of the watershed contains large expanses of undeveloped swamps and uplands. These lands are the most prevalent along the riverine corridors, including the North and South Forks up to the headwaters. In 1995, natural lands (i.e., upland forests and wetlands) comprised 26 percent of the total acreage. Water quality in the river's headwaters and the South Fork is the least affected in the watershed, corresponding to higher percentages of land in native land covers and pasture/rangeland, instead of citrus and row crops.

The Little Manatee River and Lake Manatee State Recreation Area are designated as an Outstanding Florida Water. Another feature of interest is the Little Manatee River State Park.

Human Impacts

Currently, about one-third of the Little Manatee River watershed's historical ecosystem remains, with almost two-thirds developed to some extent. Habitat loss, alteration, and fragmentation are the most critical threats throughout the watershed. Existing and proposed development (industrial, agricultural, suburban, and urban) will continue to be major agents of change. Phosphate mining continues to expand outward from the central Florida region into unmined areas of the watershed. Although agricultural activity is projected to remain constant, urbanization is projected to increase, meaning that natural areas will become smaller and/or fewer in number compared with present acreages.

Elevated nutrient and bacteria levels in the watershed are caused by runoff from agriculture (citrus and row crops) and rangelands in the upper river reaches; and agriculture, septic tanks, package wastewater treatment plants, and fish farms in the downstream reaches of the Little Manatee River. The highest loadings of total nitrogen (TN) originate in the North Fork drainage area, where agricultural land use is most extensive.

Pieces of black plastic sheeting, used extensively in row crop operations (e.g., strawberries and tomatoes) to stabilize beds and reduce the use of agricultural chemicals, end up in tributaries to the Little Manatee River or the river itself. The plastic can eventually be carried to estuarine portions of the river before drifting into Tampa Bay, and can entangle or be consumed by wildlife.

In recognition of these impacts, DEP, the SWFWMD, and local governmental, scientific, educational, and citizen organizations are working to develop strategies for protecting and restoring water quality in the Little Manatee River watershed.

Interesting Facts:

  • Lake Parrish was built by Florida Power and Light Corporation for power plant cooling.
  • Fort Lonesome was never a fort but is thought to be the site of an agricultural station set up in 1929 to inspect fruit from south Florida during a Mediterranean fruit fly outbreak. One of the inspectors reportedly hung a sign that said, "Fort Lonesome."
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