July 2022 – By definition, a river is a freshwater body flowing into a large water body such as a saltwater sea, ocean, gulf or bay. If you cut off this freshwater flow, the saltwater connection moves in, dramatically changing the ecosystem. Maintaining this flow of freshwater ensures a balanced habitat and estuary environment that is an important habitat transition and nursery for many fish and other wildlife species.
With the existence of a reservoir impoundment in the middle Hillsborough River and increasing water withdrawals due to higher demand from population growth, it was not long ago that the lower river degraded to a stagnant saltwater area for much of each year. Thanks to groups like the Friends of the River, an agreement was struck to ensure a minimum amount of flow was maintained to protect the river ecosystem. This agreement was memorialized in the Southwest Florida Water Management (SWFWMD) District’s 40-D rules, as required by Florida Statutes 373.042.
The current rules require that between 20 and 24 cubic feet per second (cfs) of freshwater flow must be maintained below the City of Tampa’s Dam depending upon the season. There is a provision in the rule that if the water used to maintain this flow contains salt and is not “fresh water” the amount of flow must be increased to account for a “freshwater equivalent.” It has been known for some time that the water used from Sulphur Springs to meet the freshwater flow is becoming saltier over time, largely because of water withdrawals from the spring. The last time this issue was studied, SWFWMD established that the appropriate freshwater flow equivalent was 23 and 27 cfs, seasonally.
Tampa staff, who operate the minimum flow regime, recently confirmed their commitment to ensuring that, at a minimum, this amount of freshwater equivalent flow will be maintained. This is an important step in efforts to maintain a healthy river for residents and visitors alike. Periodically SWFWMD will re-evaluate the effectiveness of the flow regime and the freshwater equivalent standard. In this way, the environment, residents’ quality of life, and the local economy will be maintained and improved.