Surface-water flow was measured at major creeks along the northeastern coast of Florida Bay as part of the South Florida Ecosystem Program. Water level, flow velocity, salinity, temperature, and periodic discharge measurements were collected at nine monitoring stations between US Highway 1 (US-1) and Terrapin Bay to determine the magnitude and spatial distribution of freshwater flow. Data were collected from October 1995 to present, and includes the El Nino event of 1997-98.

Mean monthly flows were used to evaluate surface-water flow patterns and to calculate net flow at the monitoring stations. About 80 percent of the measured freshwater flowing into the bay occurs during the May to October wet season. Increased precipitation associated with El Nino resulted in a 663 percent increase in total measured freshwater flow during the November to April dry season, increasing from 41 ft³/s (cubic feet per second) in 1996-97 to 273 ft³/s in 1997-98.

A comparison of flow at all monitoring stations suggests three distinct flow signatures. These flow signatures were determined as follows: (1) largest discharges occurred at Trout Creek, contributing about 60 percent of the total measured freshwater flow into northeastern Florida Bay; (2) following the El Nino event, McCormick Creek net flows were negative from October 1997 to April 1998, while the other creeks had net positive flow; and (3) net negative flows were absent at West Highway Creek during all seasons.

Evidence indicates that the greatest flow of freshwater from Taylor Slough into Florida Bay is not at Taylor River (as previously postulated), but farther east at Trout Creek. Analysis of flow data also shows that Trout Creek could be used as a long-term monitoring station to estimate total freshwater flow into northeastern Florida Bay, provided that the uncertain flow patterns at McCormick Creek and West Highway creek can be resolved.

Water level, flow velocity, salinity, temperature, and periodic discharge measurements are currently being collected at two newly installed monitoring stations that complement the existing network. The Stillwater Creek station is located in western Long Sound and the Upstream Taylor station is located about 2 miles north of an existing station at the mouth of Taylor River. Both stations will enhance the spatial resolution of flow and salinity trends and help to evaluate wind effects and storage factors in Long Sound and Taylor River.

The magnitude of discharge at Trout Creek and the water color variation along the left and right banks observed during high flows raises questions about the spatial distribution of freshwater flow entering Joe Bay. As part of a continuing effort to monitor flows in Florida Bay, discharge and salinity measurements were collected at eight creeks entering Joe Bay. Three western, one central, and four eastern creeks have been monitored on a monthly and storm-related basis since May 1999. Preliminary data suggest that greater discharges occur along the eastern and western creeks of Joe Bay as compared to the central creek. Salinity in the eastern creeks decreases rapidly and remains low after storm events or controlled-water releases; the western creeks appear to lag in salinity response time and seem to have greater fluctuations. Connection of the eastern creeks with the C-111 drainage south of structure S-18C is probable.