St. Johns River Watershed in Jacksonville, Florida

Jacksonville sits at the downstream end of the St. Johns River, a 310-mile river that flows north from marshes in Indian River County to the Atlantic Ocean at Mayport (SJRWMD).

The St. Johns River Water Management District splits the river into upper, middle and lower basins, and the lower basin is the stretch from Lake George to the river mouth at Mayport (SJRWMD lower basin). Measured by drainage area, the Lower Basin covers more than 4,500 square miles, from the Florida-Georgia line in Nassau and Baker counties south through Clay, Duval, St. Johns, Putnam and Flagler counties, and it reaches into parts of Volusia, Alachua and Bradford counties because the boundary follows the watershed rather than county lines (SJRWMD, October 2, 2026).

FDEP groups the Duval County tributaries of the St. Johns into areas that include the Ortega and Cedar rivers, the Broward River and Dunn Creek, Julington and Durbin creeks, Pablo Creek, Mill Cove and Arlington, the downtown and Southside tributaries, and the Trout River (FDEP Duval Tributary Watch). Over its full length the river falls less than 30 feet, about one inch per mile, and the district calls the St. Johns one of the laziest rivers in the world (SJRWMD).

The incoming Atlantic tide reverses the flow of the St. Johns River twice a day past Jacksonville, and in low water the reverse flow can reach Lake Monroe, 161 miles upstream from the mouth at Mayport (SJRWMD).

Strong and sustained northeasterly winds can hold the river in reverse for many days, and the district says these conditions make it difficult for the river current to naturally flush pollutants (SJRWMD). NOAA station 8720218 at the Mayport Bar Pilots Dock, established August 1, 1995, measures the tide at the river mouth (NOAA CO-OPS). It reports a mean tide range of 4.53 feet and a diurnal range of 4.96 feet. Its highest recorded water level, 3.41 feet above mean higher high water, came on November 10, 2022, and its lowest, 2.55 feet below mean lower low water, on March 8, 2008. For anyone planning a launch at a Jacksonville ramp near the mouth, the station page shows the day's predicted highs and lows next to the observed water level.

The City of Jacksonville Environmental Quality Division samples about 100 tributary sites every quarter and 10 main-river stations every month, while FDEP, the Duval County Health Department and the City publish quarterly tributary reports together (City of Jacksonville, FDEP).

The city says its tributaries supply important littoral zone habitat and can show pronounced pollution impacts because they have a smaller dilution potential than larger water bodies (City of Jacksonville). The monthly River Run samples are meant to help establish Total Maximum Daily Loads for the lower St. Johns River in Duval County (City of Jacksonville). Questions about the tributary data go to the Ambient Water Quality Section, 214 N. Hogan Street, 5th floor, Jacksonville, (904) 255-7100.

The bacteria problem is old: FDEP says it was first documented in the St. Johns River in the 1950s, and the state has identified Duval County tributaries impaired by fecal coliform as federal law requires (FDEP Duval Tributary Watch). The Jacksonville water quality guide covers river health monitoring in more detail; this guide covers how the watershed works and who manages it.

The Eighteenth State of the River Report, released in December 2025, lists 49 impaired tributaries in the lower St. Johns basin, with human sources confirmed in 41 (UNF).

Produced by University of North Florida, Jacksonville University and Penn State Berks scientists, the report takes those counts from the 2022-24 FDEP biennial assessment and says chemical tracers or genetic markers identified the human sources (UNF). Its long-term trends show total phosphorus rising in parts of the mainstem and staying high in tributaries such as Deep Creek, the commercial blue crab catch still falling, and submerged aquatic vegetation severely depleted since 2017. Protected species were described as doing relatively well.

The December 2025 release said the research team would present its findings on February 13, 2026 at the Environmental Symposium organized by the City of Jacksonville Environmental Protection Board and the UNF Institute of Environmental Research and Education (UNF). The water management district lists an annual state of the river report among the investments that followed the 1998 to 2003 River Agenda and the 2006 River Accord, alongside a citywide no net-gain goal for septic tanks in Jacksonville and Duval County and research into why tributaries are filling with silt (SJRWMD).

JEA has finished septic tank phase-out construction in Biltmore C and Beverly Hills, has begun construction in Christobel and has moved Riverview into design (JEA).

Biltmore C was completed in 2022, Beverly Hills West in 2023 and Beverly Hills East in 2024; a March 2026 JEA update says Christobel construction has begun, and Riverview met the 70 percent participation requirement on November 10, 2025 (JEA).

The water management district names partially treated wastewater, agricultural runoff, urban and suburban stormwater, and nutrients entering in the upper and middle basins as the major contributors of pollution in the lower river (SJRWMD), and the 2025 river report singles out failing septic tanks as a key contributor to tributary bacteria (UNF). JEA works neighborhood by neighborhood, and each neighborhood must reach 70 percent property owner participation, with owners completing participation documentation, before a project moves forward (JEA).

A Christobel preconstruction town meeting was held March 19, 2026 at the FSCJ North Campus Auditorium, 4501 Capper Road (JEA). JEA marks its Christobel start date as highly subject to change, so the JEA page is the place to check the current schedule.

The St. Johns River Water Management District opened public comment on its draft 2026 Lower St. Johns River Basin Plan on October 2, 2026, and it accepts comments through October 23 using the online form at sjrwmd.com/documents/plans/#basin (SJRWMD).

The draft sets priorities and projects for surface water quality, river health, flood resilience and coastal protection across the Lower Basin, including Duval County, and the district held a public meeting on September 28 to walk through it (SJRWMD). Feedback received during the comment window will inform revisions before the plan is finalized.

As of this check the comment window closes eight days after the verification date, so Jacksonville neighborhood groups, paddling clubs and property owners along tributaries such as Deep Creek have a short window to put local concerns on the record. Last verified: October 15, 2026, on the St. Johns River Water Management District website.