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The Water Channel

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Protecting Florida's Groundwater Supply

Florida's aquifer - the source of drinking water and water flowing from its springs - is vulnerable to overuse, pollution and drought. Protecting the aquifer is one of DEP's highest priorities. Learn about efforts in the Tampa Bay region to diversify water resources.

Protecting Florida's Water Supply

Hillsborough River Watershed Excursion

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Take a Virtual Trip Through the Hillsborough River Basin

Travel down the Hillsborough River from its beginnings in the Green Swamp to the mouth of Tampa Bay. (SWFWMD)

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Florida-Friendly Interactive Yard

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Learn about Florida-Friendly Landscaping Techniques

Fertilizers and pesticides used on residential and commercial landscapes are harming Florida's waterways. Find out how you can reduce your impact in your front and back yards.

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Learn About Your Watershed

Hillsborough River Watershed

Image of Rapids on the upper section of the Hillsborough River.
Rapids on the upper section of the Hillsborough River.

Watershed Stats

Size of Basin: More than 690 square miles

Counties: Hillsborough, Pasco, and Polk Counties

Major Towns: Portions of Tampa, Lakeland, Dade City, Plant City, and Land O'Lakes; all of Zephyrhills and Temple Terrace

Major Water Features: Hillsborough River and its associated tributaries, including Big Ditch, Flint Creek, Sixmile Creek (Tampa Bypass Canal), Indian Creek, New River, Two Hole Branch, Basset Branch, Hollomans Branch, Clay Gully, and Trout Creek; Clear Lake, Moon Lake, and Lakes Thonotosassa, Hunter, Iola, Pasadena, King, and Padgett; and Crystal and Sulphur Springs

Overview

The Hillsborough River begins east-northeast of Zephyrhills in southeastern Pasco and northwestern Polk Counties. Its headwaters originate in the southwestern portion of the Green Swamp, where it also periodically receives overflow from the Withlacoochee River. From the swamp, the river flows south westerly 54 miles to upper Hillsborough Bay.

Sixmile Creek was channeled to intersect the Hillsborough River in two places: at the confluence of Trout Creek and near the midpoint of the Tampa Reservoir, which supplies drinking water to the city of Tampa. The modified creek, renamed the Tampa Bypass Canal, comprises two canals: the Harney Canal (C-136) and C-135. Both canals control flooding in the city of Tampa.

Lake Thonotosassa, an 819-acre meandered lake averaging about eight feet in depth, is the largest lake in Hillsborough County. It discharges to the Hillsborough River, which provides the municipal water supply for the city of Tampa. Crystal and Sulphur Springs, located on the Hillsborough River, are second-magnitude springs with discharges of 6.46 to 64.6 million gallons per day.

Image of Wildlife is found in abundance on the Hillsborough River. The Hillsborough River Canoe Trail is officially designated as part of Florida’s Statewide System of Greenways and Trails.
Wildlife is found in abundance on the Hillsborough River. The Hillsborough River Canoe Trail is officially designated as part of Florida’s Statewide System of Greenways and Trails. Adam Baker

Large areas of undeveloped swamps and forested uplands remain along portions of the Hillsborough River and its principal tributaries. Together with other undeveloped lands, natural lands comprise 39 percent of the watershed, and urban and built-up lands make up 25 percent of the watershed's total area. Generally, the northern and central portions of the watershed are rural, primarily comprising rangeland, pasture, and agriculture, including citrus groves and row crops. They also contain the most extensive contiguous areas of natural lands remaining in the watershed. In the northern part of the watershed, urban and suburban areas appear as an east-west band encompassing Zephyrhills, Wesley Chapel, and Land O' Lakes.

The southern portions of the watershed, which include the urban and suburban areas of Tampa, Plant City, and Lakeland, are mainly urban and industrial. Tampa, the region's largest city in size and population, lies directly north of Tampa Bay in Hillsborough County. Suburban development radiating from major urban areas such as Tampa is spreading into rural areas.

A number of publicly owned tracts protect the Hillsborough River, its associated floodplain swamps, and the headwaters. These include lands managed by the Southwest Florida Water Management District (SWFWMD) in the Lower and Upper Hillsborough Flood Detention Areas, Alston Tract, Green Swamp Wilderness Preserve, Hillsborough River State Park, and Cone Ranch. These areas contain natural floodplain forests and swamps as well as mature hammocks and other natural uplands, forming a diverse landscape of wetland and upland habitats. Wildlife populations supported within these areas are significant and of regional importance. Lake Thonotosassa is designated as a Surface Water Improvement and Management (SWIM) Program priority waterbody for restoration and protection. Hillsborough River State Park is designated as an Outstanding Florida Water (OFW).

Privately owned lands form a nearly unbroken forest corridor along the Hillsborough River and include several miles of the spring-fed portions of the river created by the discharge of Crystal Springs in Pasco County. Other important areas include the cypress and mixed hardwoods swamps associated with Cypress Creek and other tributaries to the Hillsborough River.

Human Impacts

The scope and rapid rate of population growth throughout the watershed have imposed widespread changes on the landscape, as natural lands were cleared and developed. Natural vegetation communities, which provide essential habitat for fish and wildlife, are permanently altered in many areas, particularly in the lower and middle reaches of the Hillsborough River. The proliferation of exotic (nonnative) invasive plant species threatens both native plant communities and wildlife populations.

Downstream from the river's headwaters in the Green Swamp, increased concentrations of nitrate-nitrogen from fertilizers in the ground water flowing from Crystal Springs have increased nutrient levels to the Hillsborough River. Water quality in Big Ditch, which enters the river two miles below Crystal Springs, has historically been poor due to rangeland runoff. The largest tributary to Blackwater Creek, Itchepackesassa Creek, is a channelized stream with a history of poor water quality; it has experienced low concentrations of dissolved oxygen (DO) and periodic fish kills.

Image of The river's character changes dramatically as it approaches Tampa Bay. Throughout the watershed, rapid population growth has imposed widespread changes on the landscape, as natural lands were cleared and developed.
The river's character changes dramatically as it approaches Tampa Bay. Throughout the watershed, rapid population growth has imposed widespread changes on the landscape, as natural lands were cleared and developed.

Water quality in the New River, Two Hole Branch and Hollomans Branch has been affected by livestock, stream channelization, and aquatic weeds. Basset Branch has been affected by land disposal, urban and construction runoff, and hydrologic modification. Periodic episodes of elevated bacteria have closed Hillsborough River State Park to swimming. Mill Creek and Spartman Branch historically had poor water quality due to their urban nature and the former influence of the Plant City wastewater treatment plant, which contributed up to 40,000 pounds of phosphorus per year to Mill Creek.

The upper Cypress Creek drainage area, which is undergoing residential development, has poor water quality. In other reaches of the lower river, including the Tampa Reservoir, poor water quality remains a concern. The reservoir has changed the free-flowing character of portions of the lower river since the 1920s.

During the excavation of the Tampa Bypass Canal in the early 1960s, the upper Floridan aquifer was breached at several points, resulting in hydraulic connections between the canal waters and the aquifer; these periodically affect water quality in the canal. The lower segment of the Hillsborough River has water quality problems from urban runoff and significant habitat loss caused by hardening of the riverbanks with seawalls.

Before 1970, water quality in Lake Thonotosassa and its tributary streams was degraded over a period of several decades by nutrient-enriched effluent from the Plant City wastewater treatment plant, agricultural and urban stormwater runoff, and industrial wastewater generated by food-processing facilities. The lake is highly eutrophic, with frequent blooms of algae, low levels of DO, and periodic fish kills. Large volumes of flocculent muck in the deeper areas of the lake may contribute to poor water quality. Lake Thonotosassa is drained by Flint Creek, which also has poor water quality.

Sulphur Springs has been closed to swimming since 1986 due to high bacteria levels. The contamination may be caused by direct connections to at least two sinkholes that were converted to stormwater detention ponds by the city of Tampa.

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 Hillsborough River watershed.


Interesting Facts:

  • Just north of U.S. Highway 98 near the Pasco/Polk County line, a portion of the Withlacoochee River's flow is periodically conveyed to the Hillsborough River across a broad expanse of swamp. This area of "shared flow," called the Hillsborough/Withlacoochee Overflow, and the surrounding forested swamps are essential to maintaining the natural hydrology and wetlands of both rivers.
  • The Hillsborough River contains Class II rapids; although closed to boating, they can be viewed from a location in Hillsborough River State Park.
  • During the drier times of the year, little or no water is released from the Tampa Reservoir.
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