Freshwater flows are essential to the lower Hillsborough River

November 2017 – Per Chapter 86‐335, Laws of Florida, the Hillsborough River Interlocal Planning Board and Technical Advisory Council monitors development and other activities associated with the river to maintain the health and integrity of the river for the benefit and enjoyment of the residents of Hillsborough County. Rivers are dynamic systems that carry water downstream to a sea or bay.  They are freshwater systems with an estuarine area where the fresh water meets saltwater.  These areas are critical habitats for many marine fish that use the estuarine area for a portion of their lifecycle.

Historically, the City of Tampa Dam on the Hillsborough River at Rowlett Park was originally constructed to produce electricity to power Tampa’s street car system. The streetcars were later replaced with buses, and the power generation plant was later decommissioned. As Tampa’s growing population needed additional drinking water supplies, the City of Tampa used the water held behind this dam for public supply.

Over the years, increasingly more water was withdrawn annually from this reservoir.  Subsequently, the number of days each year fresh water flowed downstream to the lower river and Tampa Bay began to dwindle. With little, or no, fresh water in the lower river for much of the year, the estuary suffered and this part of river became more of a stagnant bay. Citizens began to take notice and worked to urge the City and State to establish a minimum amount of freshwater flow to keep the lower river a healthy estuary.

In 2007, a minimum flow for the river was established. The recovery strategy adopted with the minimum flow rule for the Lower Hillsborough River in 2007 required that in 2013, and for each five-year period through 2023, the Southwest Florida Water Management District (SWFWMD) would evaluate the hydrology, dissolved oxygen, salinity, temperature, pH and biologic results achieved from implementation of the recovery strategy for the previous five years, including the duration, frequency, and impacts of the adjusted minimum flow.

In March of 2015 the report “A Hydrobiological Assessment of the Phased Implementation of Minimum Flows for the Lower Hillsborough River” was released by SWFWMD. This report concluded that the establishment of the minimum flow was successful, and no additional changes to flow were recommended at that time. The report and its data were reviewed by the River Board & Technical Advisory Council to ensure the minimum flow and recovery plan are sufficient.


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