Withlacoochee River System Update - 5/1/2024

Water Levels/Flows Decline from Less Rainfall

 

Rainfall:

• A wetter than average winter gave our water resources a nice boost over the past several months of the dry season.
• Last month, however, was the first time since October that our region’s rainfall was below average, and water levels are now dropping as a result.
• In April, we averaged 1.9 inches of rain, less than the historical average (2.8 inches) for the month.
• So far this year (January through April), our region has received 13.0 inches of rain, slightly higher than the historical average (12.3 inches) for the first 4 months of the year.
• Less rainfall this time of year equates to lower water levels because stream flows are decreasing, and evaporation is higher.
• Trees and plants are also starting to grow, using more water from the surface and ground.
• Aquifer (groundwater) levels are declining and are currently in the 43^rd percentile, below average for our region, and very close to this date last year (40^th percentile).
• The figure below shows how much rainfall different areas received last month.

 

 

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

• After defying normal trends and rising during much of the dry season (winter/spring), river levels are now steadily declining.
• Over the past four weeks, water levels along the upper half of the Withlacoochee River, from the Green Swamp past Hwy 50, have dropped about 16 inches.
• Farther downstream, from Nobleton past Hwy 200, river levels have declined about 7 inches over the past month.
• There is essentially no flow leaving the Green Swamp (start of the river) as wetlands begin to dry up from minimal rainfall.  
• In fact, there is very little flow along much of the river now, until you reach Hwy 44 and 200, where several spring-fed tributaries join the Withlacoochee.
• If you enjoy kayaking or canoeing the river, it’ll take a little more effort right now, with less natural flow.
• The table below compares current river levels and flows to what they were last month and last year.

 

 

Withlacoochee River past Hwy 200 (April 2024)

 

 

Tsala Apopka Chain of Lakes:

• For the first time in months, water levels have dropped on all three pools of the Tsala Apopka Chain of Lakes.
• In April, the Floral City Pool fell about 6 inches, while the Inverness and Hernando Pools declined 4 inches.
• Despite these declines, lake levels remain quite a bit higher than they were a year ago at this time.
• Water control structures were closed in early April as river levels have fallen and inflow is no longer available to the lake chain.
• Structures will likely remain closed, helping to conserve water in the lakes, until summer rains increase regional water levels again.
• All three pools are currently about a foot below their normal high levels, a target not typically reached until late in the wet season (Aug-Sept).

 

 

Lake Panasoffkee and Wysong:

• Lake Panasoffkee also peaked in early April and has been steadily dropping over the past few weeks.
• Last month, water levels fell nearly 6 inches, due to low rainfall and less inflow from the spring-fed creeks to the east.
• Stream flows in Shady Brook and Little Jones Creek, which provide continuous inflow to the lake, declined by 40% in April but remain higher than a year ago.
• Lake Panasoffkee is currently 12 inches higher than it was last May, due to above average rainfall from November to March.
• Outflow from Lake Panasoffkee to the Withlacoochee River also declined last month but is still higher than a year ago.
• A few miles downstream along the Withlacoochee River, the Wysong Structure remains partially inflated.
• The main gate (230-ft-wide) at Wysong is fully raised.
• The independent gate (19-ft-wide) remains partially raised, allowing river flows to pass downstream.
• Flow in the Withlacoochee River at Wysong is currently twice as high as it was a year ago.

 

 

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

• Downstream from Dunnellon, the Withlacoochee River is influenced by water control structures on Lake Rousseau.
• Inflow to Lake Rousseau includes combined flows from the Withlacoochee and Rainbow Rivers.
• Rainbow River flow (which reflects changes in aquifer levels) fell 3% in April but is currently 9% higher than a year ago.
• Withlacoochee River flow (which depends on rainfall and runoff from adjacent lands) fell 32% last month but is still nearly double what it was a year ago.
• Overall, inflows to Lake Rousseau are 27% higher than they were last year, due to higher rainfall this past winter.
• The Rainbow River is currently providing nearly two-thirds the total flow entering Lake Rousseau.

 

Great blue heron guards the Lake Rousseau backwaters (April 2024)

 

• The primary outlet from Lake Rousseau is through the Inglis Bypass Spillway to the Lower Withlacoochee River (see maps below).
• When the Bypass Spillway reaches its capacity, the Inglis Main Dam is opened to discharge excess flows to the Barge Canal.
• Currently, the Bypass Spillway is flowing at around 60% of its 900 MGD capacity, which is 41% more flow than a year ago.
• The Inglis Main Dam remains closed and won’t be open again until the Bypass Spillway reaches its capacity.
• Freshwater flow from Lake Rousseau to the Lower Withlacoochee River declined by 24% in April.

 

 

Best regards,

Mark

 

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

Chief Professional Engineer

Water Resources Bureau

Southwest Florida Water Management District

 (352) 269-6073 (office)

(352) 279-4493 (cell)

Mark.Fulkerson@WaterMatters.org

 Withlacoochee River Watershed Initiative