Withlacoochee River System Update - 3/1/2021

February Rainfall Boosts Water Levels and River Flows

 

Rainfall:

• Over the past few months, river flows and water levels have been dropping, which is normal during Florida’s dry season (October to May).
• That trend came to a temporary halt in February.
• Over the past month, our region received 4.3 inches of rainfall, which is higher than the historical average (3.0 inches).
• Higher rainfall in February provided a slight boost to our region’s water resources.
• Over the past 12 months, we’ve received about 49.5 inches of rain, which is 4 inches below average (53.6 inches) for that time.
• Aquifer (groundwater) levels are currently in the 50^th percentile, exactly average for March but lower than where they were a year ago (68^th percentile).

 

Withlacoochee River (from the Green Swamp downstream past Hwy 200):

• Water levels and flows along the Withlacoochee River rose in February thanks to some much-needed rainfall.
• River levels are currently 2-3 inches higher than they were a month ago.
• River flows increased by an average of 14% over the past month.
• Despite these recent gains, water resource conditions along the Withlacoochee River are expected to continue to naturally decline over the next few months as our dry season continues.
• Currently, river levels and flows remain lower than they were a year ago, as seen in the table below.

 

 

Withlacoochee River at Iron Bridge Recreation Area (State Forest) 

 

Tsala Apopka Chain of Lakes:

• From November through January, water levels throughout the Tsala Apopka lake chain had fallen 6-8 inches.
• In February, however, there was enough rain to hold lake levels steady.
• As a result, water levels in all three pools of Tsala Apopka are currently about 4 inches higher than they were a year ago.
• The next few months (March to June) are when we typically see sharp declines in water levels due to warmer temperatures and higher evaporation.
• How far the lakes drop this spring will depend on how much rainfall we get in the coming weeks.
• The water control structures (aka “locks”) remain closed, helping to conserve water in Tsala Apopka.

 

Tussock Lake - Floral City Pool 

 

Lake Panasoffkee and Wysong:

• Lake Panasoffkee provides flow to the Withlacoochee River, thanks to a continuous supply of water from the aquifer and adjacent spring-fed creeks.
• Over the past month, water levels in Lake Panasoffkee rose about 3 inches, due to increased rainfall and creek inflows.
• Lake Panasoffkee is currently a few inches lower than it was a year ago.
• Inflows to the lake from Little Jones Creek and Shady Brook increased by 17% in January.
• Outflows from the lake to the Withlacoochee River slightly decreased over this time.
• The main gate of the Wysong structure remains raised, helping to conserve water immediately upstream and in Lake Panasoffkee.
• The boat lock at Wysong is operational again (via self-service).

 

Lake Rousseau and the Lower Withlacoochee River (from Dunnellon to the Gulf of Mexico):

• Lake Rousseau is an in-stream reservoir, created 112 years ago (1909) when the original Inglis Dam was built on the Withlacoochee River.
• Upstream of Lake Rousseau, flow from the Rainbow River combines with flow in the Withlacoochee River near Dunnellon.
• Over the past month, contributing Withlacoochee River flows increased by 8% while Rainbow River flows remained fairly steady.
• Flow in the Rainbow River is about 12% lower than it was a year ago, due to less overall rainfall the past 12 months.
• The Rainbow River is currently providing more flow to Lake Rousseau than the Withlacoochee River is, a common occurrence during the dry season.
• Overall, inflows to Lake Rousseau have increased by about 3% over the past month but are 13% lower than they were a year ago.

• Outflows from Lake Rousseau are controlled by the Inglis Main Dam (to the Barge Canal) and the Inglis Bypass Spillway (to the Lower Withlacoochee River).
• The Inglis Main Dam is only open when flow leaving Lake Rousseau exceeds the capacity of the Inglis Bypass Spillway.
• Currently the Inglis Dam is closed, and all flow is passing from Lake Rousseau to the Lower Withlacoochee River.
• Rainfall in February effectively increased freshwater flow to the Lower Withlacoochee by around 7%.
• Work is set to begin in March to collect better bathymetry (bottom elevations) along the entire Lower Withlacoochee River.
• These new data will help support the ongoing MFL study.

 

As always, let me know if you have any questions or concerns. Take care and have a great week!

Mark

 

Mark Fulkerson, Ph.D., P.E.

Chief Professional Engineer

Water Resources Bureau

Southwest Florida Water Management District

 (352) 796-7211, ext. 4410

(800) 423-1476 (FL only)

(352) 279-4493 (cell)

Mark.Fulkerson@WaterMatters.org

 Withlacoochee River Watershed Initiative