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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

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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

Tampa Bay Watershed

Image of Rowers ply the waters of Tampa Bay between Harbor and Davis islands.
Rowers ply the waters of Tampa Bay between Harbor and Davis islands. © Steve Tamargo

Watershed Stats

Size of Basin: 400 square miles of open water, with a 2,200-square-mile drainage basin

Counties: Bordered by Hillsborough, Manatee, and Pinellas Counties

Major Towns: Surrounded by the Tampa metropolitan area and portions of Clearwater, St. Petersburg, Largo, and Bradenton

Major Water Features: More than 100 tributaries and more than 40 meandering, brackish creeks and coastal streams flow into the bay, including the Hillsborough River, Alafia River, Manatee River, Little Manatee River, Palm River, Tampa Bypass Canal, Delaney Creek, Bullfrog Creek, Cross-Bayou Canal, Lake Tarpon Canal, Rocky Creek, Sweetwater Creek, Allen Creek, Alligator Creek, Bishop Creek, Wolf Branch, Cockroach Creek, Booker Creek, and Salt Creek

Overview

Image of Tampa Bay, the largest open-water estuary in Florida, extends approximately 35 miles inland from the Gulf of Mexico and is 5 to 10 miles wide along most of its length.
Tampa Bay, the largest open-water estuary in Florida, extends approximately 35 miles inland from the Gulf of Mexico and is 5 to 10 miles wide along most of its length. © Diana K Williams, DEP

Tampa Bay, the largest open-water estuary in Florida, extends approximately 35 miles inland from the Gulf of Mexico and is 5 to 10 miles wide along most of its length. Four segments make up the open-water section. Hillsborough Bay, the smallest of these segments, receives runoff from a large portion of the city of Tampa. The Hillsborough and Alafia Rivers drain into Hillsborough Bay, as do a number of smaller tributaries. Middle Tampa Bay receives runoff from the Little Manatee River and drainage from smaller tributaries along the Hillsborough and Pinellas County coastlines. Old Tampa Bay receives runoff from portions of Clearwater, St. Petersburg, and Tampa. Lower Tampa Bay, which has the largest volume of the four segments, connects the mouth of the bay to the Gulf of Mexico. The Manatee River, which receives runoff from the city of Bradenton, flows into the southern portion of this bay segment.

Four other segments constitute the drainage basins of coastal tributaries that flow directly to the bay: the Coastal Lower Tampa Bay area lies along the eastern side of Lower Tampa Bay, the Coastal Middle Tampa Bay area consists of the eastern and western shores of Middle Tampa Bay, the Coastal Hillsborough Bay area borders Hillsborough Bay to the northeast, and the Coastal Old Tampa Bay area surrounds the northern and western sides of Old Tampa Bay.

The Hillsborough, Alafia, Manatee, and Little Manatee Rivers contribute significant flows to Tampa Bay, including flows from at least three second-magnitude springs (with discharges of 6.46 to 64.6 million gallons per day): Crystal and Sulphur Springs on the Hillsborough River and Lithia Springs on the Alafia River.

Tampa Bay contains more than 200 fish species, including snook, redfish, and spotted sea trout. Its mangrove-blanketed islands support the most diverse colonial waterbird nesting areas in North America.

Because the bay averages only about 12 feet in depth, channels have been dredged to allow large ships safe passage to the Port of Tampa, Florida's largest port, and other harbors. The port consistently ranks among the top 10 ports nationwide in tonnage and contributes billions annually to the region's economy.

Tampa is the region's largest city in size and population. In 1995, the Greater Tampa Bay region contained about 3.6 million people, concentrated in the Tampa Bay metropolitan area. The population is expected to grow to about 4.6 million permanent residents by 2010, with the largest increase projected in the developed areas surrounding Tampa Bay (Hillsborough, Pasco, Manatee, and Pinellas Counties).

Image of Weedon Island Preserve is an approximately 3,164-acre preserve that extends along the west side of Tampa Bay in Pinellas County. It is the largest estuarine Preserve in the county, and is predominately comprised of aquatic habitats with mangrove swamps, shoreline, and seagrass beds.
Weedon Island Preserve is an approximately 3,164-acre preserve that extends along the west side of Tampa Bay in Pinellas County. It is the largest estuarine Preserve in the county, and is predominately comprised of aquatic habitats with mangrove swamps, shoreline, and seagrass beds. © Weedon Island Preserve

The Tampa Bay Basin contains some of the state's most productive agricultural lands. Other significant components of the region's economy include phosphate and other mining, industry and power generation, and tourism and recreation.

Tampa Bay contains more than 200 fish species, including snook, redfish, and spotted sea trout. Its mangrove-blanketed islands support the most diverse colonial waterbird nesting areas in North America. The bay contains 29 species of colonial waterbirds and allied species, totaling about 44,000 breeding pairs and their young (nearly 200,000 birds). Up to half of these are found in Hillsborough Bay. A number of listed bird species are found in the Tampa Bay system. Other listed species include the West Indian manatee and the green, Kemp's ridley, hawksbill, and loggerhead turtles.

Seagrasses are found in the bay's shallow waters. Because they require light to grow, anything that limits light penetration into the water causes them to decline. Sediments of sand or mud up to 65 feet thick cover about 80 percent of the bay, sheltering benthic organisms such as worms, crustaceans, clams, mollusks, tunicates (or sea squirts), and larvae. Both seagrasses and benthic species are important indicators of the system's ecological health.

The principal factors affecting species and natural communities baywide are water temperature, water clarity and color, nutrients, water quality, dissolved oxygen (DO) levels, wind, freshwater flows, tidal flows, salinity levels, sediment characteristics, and the bay's physical structure. Almost all of these are significantly influenced by contributions that the bay receives from upstream, such as organic and inorganic matter, freshwater flows, and stormwater runoff.

The following waterbodies in the basin have been given additional protection through designation as Outstanding Florida Waters (OFWs):

  • Hillsborough River State Park, Hillsborough Bay;
  • Cockroach Bay Aquatic Preserve, Coastal Middle Tampa Bay;
  • Little Manatee River, Middle Tampa Bay;
  • Terra Ceia State Aquatic Preserve, Coastal Lower Tampa Bay;
  • Boca Ciega State Aquatic Preserve, Lower Tampa Bay;
  • Pinellas County Aquatic Preserve, Lower Tampa Bay, which encompasses all submerged sovereign lands in the county; and
  • Lake Manatee State Recreation Area, Manatee River.

The bay's four state Aquatic Preserves (Cockroach Bay, Terra Ceia, Boca Ciega, and Pinellas County) encompass more than 370,000 acres.

Human Impacts

Image of The Tampa Bay region is one of the most heavily developed and urbanized areas of Florida. During the 1950s to the 1970s, extensive habitat destruction and water quality impacts occurred in the bay, caused by industrial. commercial and residential shoreline development. Today, stormwater runoff carrying fertilizers, chemicals and other pollutants continues to threaten the bay.
The Tampa Bay region is one of the most heavily developed and urbanized areas of Florida. During the 1950s to the 1970s, extensive habitat destruction and water quality impacts occurred in the bay, caused by industrial. commercial and residential shoreline development. Today, stormwater runoff carrying fertilizers, chemicals and other pollutants continues to threaten the bay. © DEP

Runoff from the basin's 10 major drainage areas provides essential fresh water to Tampa Bay. However, the runoff also contains excess nutrients and other pollutants from nonpoint sources, atmospheric deposition, point sources, ground water, septic tank lechate, and wastewater residual solids. Excess nitrogen accelerates algae growth, limiting the amount of light reaching seagrasses and reducing DO levels. Urban and agricultural nonpoint sources contribute almost half of the bay's annual nitrogen load.

Seagrasses in the bay-especially in the upper portion-decreased as much as 80 percent between the late 1800s and the late 1900s because of dredging, pollution, and reduced water clarity. Nitrogen pollution was most serious from the late 1960s to the early 1980s, when partially treated sewage was discharged to the bay, leading to algal blooms. By 1982, only 21,600 acres of seagrasses remained, and Hillsborough Bay's 2,700 acres had almost completely disappeared. Nitrogen loading continues to be a major concern. Baywide, it is expected to increase 7 percent by 2010, or about 17 tons per year, as a result of population growth.

Seagrasses in the bay-especially in the upper portion-decreased as much as 80 percent between the late 1800s and the late 1900s because of dredging, pollution, and reduced water clarity.

From the 1950s to the 1970s, extensive habitat destruction and water quality impacts occurred in the bay, caused by shoreline development-primarily dredge-and-fill projects to develop navigational channels, waterfront communities, and industrial sites. The dredging of navigational channels and the underwater disposal of dredged material affected almost 15,000 acres of bay bottom, mostly in deep-water areas. Another 1,200 acres were filled to create spoil islands and causeways.

Both historically and in recent years, Hillsborough Bay has had the poorest water quality of the major bay segments. The bay and its drainage basins have the highest number of point source facilities in the region, including 16 domestic wastewater facilities and 32 industrial facilities, primarily involved in phosphate mining and fertilizer manufacturing. Historically, the stations on the Alafia River had high phosphorus concentrations from phosphate mining and processing operations in the upper reaches that influenced phosphorus levels in Hillsborough Bay.

Other issues in the basin include elevated levels of fecal coliform bacteria from agricultural and urban stormwater runoff, sewage treatment plants, septic systems, and sewer overflows; and decreased levels of DO from the breakdown of organic matter.

During heavy rains in 1997, a dike broke at Mulberry Phosphates in Polk County; 55 million gallons of acidic wastewater flowed into the Alafia River, killing more than 1 million fish. In 2001, the bankrupt Mulberry Corporation abandoned both the Mulberry facility and the Piney Point Phosphates fertilizer plant in the Coastal Lower Tampa Bay region. DEP assumed the responsibility for cleaning up a 1.2 billion gallon acidic wastewater spill and the management of the 70-foot phosphogypsum stacks. It is attempting to implement a phased closure plan at Piney Points by treating and removing the wastewater on site.

While populations of most of the bay's coastal bird species have increased, the numbers of wading birds that forage in freshwater wetlands have declined. Of particular concern is a recent sharp decline in white ibis populations. Manatee deaths increased between 1985 and 1997. This species is extremely vulnerable to injuries from boat propellers; entrapment or crushing in locks, dams, and culverts; surface water pollution and the associated loss of seagrasses as a food source; and entanglement in fishing nets and lines. Turtle populations were depleted from overhunting by the end of the 19th century.

More than four billion gallons of oil, fertilizer products, and other potentially hazardous materials pass through Tampa Bay each year, creating the potential for spills. In large urban centers, ports, and marinas along the shoreline, a number of potentially toxic substances have been found in relatively high concentrations in sediments. Most enter the bay through urban runoff and atmospheric deposition. Other issues include fish consumption advisories for mercury, invasive exotic species such as the Asian green mussel, and periodic blue-green algae blooms.

In recognition of these impacts, DEP, the Southwest Florida Water Management District (SWFWMD), and local governmental, scientific, educational, and citizen organizations are working to develop strategies for protecting and restoring water quality in the Tampa Bay watershed.

Interesting Facts:

  • Tampa Bay's mangrove-blanketed islands support the most diverse colonial waterbird nesting areas in North America, ranging from the familiar white ibis and great blue heron to the black skimmer, royal tern, and reddish egret-the rarest heron in the nation.
  • The coastal portions of the Tampa Bay system contain the only known nesting colony of Caspian terns in Florida.
  • Gulf sturgeon were briefly fished commercially in Tampa Bay beginning in 1886, when about 1,500 fish were caught. By 1889, the catch was only seven fish.
  • More than 500 types of macroinvertebrates have been found baywide, and each square meter of sediment contains an average of 10,000 animals.
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