Rainfall in September slightly below average Districtwide

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Map and table showing rainfall in August 2021
Map and table showing rainfall in August 2021

A map illustrates rainfall conditions in September across the St. Johns River Water Management District.

PALATKA, Fla., Oct. 12, 2021 — While it is still storm season around the St. Johns River Water Management District, September brought rainfall slightly below the long-term average.

A full report outlining September’s hydrologic conditions was presented at the District’s Governing Board meeting Tuesday. Highlights include:

Rainfall

  • Districtwide, September rainfall averaged 6.14 inches, which is 0.60 inches below the long-term average for the month.
  • Counties with the highest rainfall totals are Seminole, with 8.3 inches of rain, followed by Marion, with 8.25” and Alachua, with 7.9”
  • The counties with the least rainfall in September were Nassau County with 4.45 inches, and Duval County with 4.5 inches.
  • Districtwide, the cumulative rainfall total for the past 12 months is 51.48 inches, which is 0.47 inches above the long-term average.

Groundwater 

  • Upper Floridan aquifer conditions (groundwater levels) at the end of September were either in the high or normal range throughout the District. Water levels in many of the wells used for this report increased more than 10 percentile points during the month.
  • Groundwater levels are at the 87th percentile Districtwide. This means that since 1980, aquifer levels have been higher than they currently are about 13 percent of the time.

Surface water flows

  • On Oct. 1, flow in most stations across the District was in the average range. The two exceptions were the St. Johns River at Jacksonville station, which had flow in the low range, and the St. Johns River at DeLand station which exhibited high flow on Oct. 1.
  • On Oct. 1, flow in the St. Johns River’s headwaters at the Melbourne station was 662 million gallons per day (mgd) (40th percentile).
  • Flows in the Econlockhatchee River near Chuluota were in the average range at 486 mgd (73rd percentile).
  • Flows in the Wekiva River near Sanford were in the average range at 203 mgd (57th percentile).
  • Flows at the DeLand station were in the high range at 4.7K mgd (76th percentile).
  • Flows in the Ocklawaha River, the largest tributary to the St. Johns River, were in the average range at 693 mgd (62nd percentile).
  • Flows at the St. Johns River near Satsuma station were in the average range at 6.4K mgd (73rd percentile).
  • Flows in the St. Marys River near Macclenny were in the average range at more than 632 mgd (75th percentile).

Lake levels

  • Lake Brooklyn water levels increased 0.7 foot to 100.8 feet in September.
  • Lake Weir increased by 0.2 foot to 53.8 feet.
  • Lake Apopka’s water levels remained steady at 65.7 feet. Lake Apopka’s water levels are being maintained at its regulation schedule. Lake Apopka is part of a system with water control structures that are operated by the District to reduce flood impacts, and the lake level is regulated according to a specific schedule.
  • Blue Cypress Lake levels increased to 22.2 feet, slightly above the regulation schedule for this time of year. Blue Cypress is also part of a system with water control structures that are operated by the District. During April and May, the regulation schedule levels begin to drop in preparation for the summer wet season.

Spring flows

  • The mean monthly flow at Silver Springs increased to 803 cubic feet per second (cfs), or 519 mgd, which is a 42 cfs increase from August’s mean.
  • At the Blue Spring station in Volusia County, the mean monthly flow was 140 cfs, or 90 mgd.
  • At Rock Springs, the monthly mean flow increased 1 cfs to 65 cfs (42 mgd), which is in the high range for September.
  • Mean monthly flow at Wekiwa Springs increased slightly to 67 cfs (43 mgd), which is in the normal range for the time of year.

To learn more about rainfall totals and other hydrologic data collected, visit sjrwmd.com.

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