Hillsborough River Dam and Reservoir in Tampa, Florida

The Hillsborough River Dam is the City of Tampa's water supply dam in Sulphur Springs, holding back the reservoir that is the city's primary drinking water source.

The Hillsborough River Dam is the City of Tampa's water supply dam on the lower Hillsborough River in Sulphur Springs. Behind it lies what the City of Tampa Water Department calls the 1.2 billion gallon Hillsborough River Reservoir, the city's primary drinking water source. The dam turns the river above Sulphur Springs into a long, narrow pool from which the David L. Tippin Water Treatment Facility, on the riverbank near 30th Street, draws its raw water.

A federal study gives the engineering outline. The U.S. Geological Survey Water-Resources Investigations Report 78-29 describes the Tampa Reservoir Dam as built in 1945 on the lower Hillsborough River 10 miles above its mouth, holding 12.5 miles of the natural river channel as storage. The present structure replaced an earlier hydroelectric dam at the site owned by the Tampa Electric Company, which a 1933 flood breached.

Tampa built its own water plant on the Hillsborough River in the 1920s after the early private water company could not reliably supply a growing city.

Tampa began with private water. The City of Tampa history slideshow records that the town's population in 1882 was 499 and that its first water company was Tampa Water Works, a private company, with published water rates and rules dating to 1892. According to the Water Department's 1926 production plant page, after that early privately owned company had difficulty giving a growing city a reliable supply of drinking water, city leaders built a municipal water treatment plant on the banks of the Hillsborough River in an area that was then remote.

The river was the obvious source because of where it comes from. The Tampa Water Department treatment process page explains that by the time Hillsborough River water reaches the plant it has traveled over 50 miles southwest from the Green Swamp, and that its tea-like color comes from natural organic matter released by decomposing vegetation in the swampy flatlands. The department reports delivering 82 million gallons of water a day to close to 717,000 people, which is the demand the Sulphur Springs dam and reservoir are built to meet.

A September 7, 1933 flood washed out the Tampa Electric Company dam, and the City of Tampa rebuilt and expanded it between 1944 and October 1945.

The site was a power dam long before it held Tampa's water. A Tampa Water Department Engineering Division timeline of key dates, attached to a 2014 city solicitation, records that Consumers' Electric Light and Street Railroad Co. bought the site in April 1895 and finished a wood crib hydroelectric dam in 1897, and that the Tampa Electric Co. bought those assets on October 2, 1899. On September 7, 1933, a flood of record with a peak flow of 16,500 cubic feet per second washed away the south embankment; Tampa Electric suspended operations and later abandoned the dam, and the loss of reservoir storage significantly affected the city's Water Works.

The same timeline traces the handover. On May 26, 1944, Tampa Electric deeded the dam and related properties to the City for $1, with a proviso that the City would owe Tampa Electric $42,222 if it ever generated electricity there. The City awarded a $148,000 contract for the dam expansion on August 30, 1944, broke ground on October 4, 1944, and completed the reconstruction and expansion, without a hydroelectric component, in October 1945.

The City of Tampa's water history slideshow gives shorter, slightly different dates. Its caption for the TECO Dam says the dam was rebuilt in 1944, and it adds that 1960 flooding in Tampa damaged the dam and that new crest tainter gates were installed in 1963 and 1964. The engineering timeline instead records flash boards at the crest failing on August 2, 1960, and a crest superstructure with a walkway and fifteen crest gates completed on March 7, 1962, so the two city sources do not agree on the gate dates. The timeline also lists later work: the dam was the first in Florida inspected by the U.S. Army Corps of Engineers under the federal program, in January 1978; crest gates were replaced and the south abutment strengthened by 1999; the north and south tainter gates were replaced in October 2001; and walkway and electrical upgrades were completed in June 2013.

The dam sits beside an older city investment. The Water Department's plant history records that in 1924 construction began on a water treatment plant on the Hillsborough River near 30th Street, while the engineering timeline dates the start to 1923 and places the plant about 1.5 miles upstream of the dam; and that the original filter house, completed in 1925, is still in use after several expansions. The plant is designated an American Waterworks Landmark, and the city notes that its original high speed pumps, once driven by steam turbines, now run on electric motors.

The City of Tampa puts the Hillsborough River Reservoir at 1.2 billion gallons, while a 1976 USGS study calculated 2,000 million gallons of usable capacity.

Figures differ by date and method. The 1976 USGS study calculated that, excluding dead storage, Tampa Reservoir capacity is 2,000 million gallons at a maximum stage of 22.5 feet above mean sea level. The City of Tampa's current description, on a Water Department page updated October 1, 2023, gives the Hillsborough River Reservoir as 1.2 billion gallons.

USGS also measured how reliable the reservoir is in drought. Flow of the lower Hillsborough River and storage behind the Sulphur Springs dam become deficient during annual dry periods, the report found, and in any year at full capacity Tampa Reservoir and the river have a 5 percent chance of failing to supply at least 66 million gallons of water per day and a 2 percent chance of failing to supply at least 59 million gallons per day.

Those limits explain the backups described on the Tampa Water Department About Us page. The Tippin plant can produce up to 120 million gallons a day at peak and averages 82 million gallons a day over a year. When excess water is available, up to 1.2 billion gallons is stored in the city's Aquifer Storage and Recovery System, and when the river cannot meet demand in extended dry periods, Tampa buys treated groundwater, surface water and desalinated seawater from Tampa Bay Water.

SWFWMD can divert Hillsborough River runoff through the Harney Canal into the Tampa Bypass Canal, a few miles north of the city's dam.

The dam holds water for drinking, but it sits downstream of the Four Rivers flood control system, whose Tampa Bypass Canal component the engineering timeline says became operational in November 1978, and which the Southwest Florida Water Management District (SWFWMD) operates. SWFWMD's WaterMatters magazine for November to December 2004 explains that the Harney Canal and Structure 161 were built to divert runoff from the 192-square-mile drainage area between the Lower Hillsborough Flood Detention Area and the Hillsborough River Reservoir Dam. District staff work with the City of Tampa to decide how much water to divert, striking a balance between flood protection and keeping appropriate levels in the city's water supply reservoir.

The SWFWMD Tampa Bypass Canal System page places the Harney Canal a few miles north of the City of Tampa's dam and says the canal is opened when inflows below the District's earthen dam cause river flooding. SWFWMD adds that this route is especially useful when discharges from the city's dam are impeded by storm surge from a hurricane.

The dam has had recent repair work, and since April 3, 2026 Tampa's water shortage status tied to the reservoir has been Modified Phase III Extreme.

The structure needs periodic repair. The City of Tampa Contract Administration office posted bid 21-C-00012, Hillsborough River Dam North Embankment Remediation, on January 27, 2021, with bids opened on March 16, 2021, and posted an award document on the same project page.

Drought puts the reservoir at the center of Tampa water rules. The city's watering days page states that Tampa's water use restrictions have been in place and enforced year-round since 1992, and that a Modified Phase III Water Shortage Order was passed by SWFWMD on March 24, 2026. On October 18, 2026, the page, last updated July 22, 2026, still showed the current water shortage status as Modified Phase III Extreme, effective April 3, 2026.

Low, warm reservoir water also shows up at the tap. The City of Tampa water FAQs explain that a lack of rainfall combined with rising daytime temperatures can cause algae blooms in the Hillsborough River Reservoir that temporarily give Tampa's water an earthy taste and odor while it is being treated. The same FAQs report that hardness of water drawn mainly from the Hillsborough River ranges from about 140 to 300 parts per million, lower in the wet season and higher in the dry season.

Last verified: October 18, 2026, by re-reading the Tampa Water Department history, plant, treatment, About Us, FAQ and watering pages, the department's 2014 dam timeline, the 2021 embankment bid page, two SWFWMD pages and the USGS 1976 report.