Water district reports on high-water levels

By Mark Fulkerson, Ph.D., P.E.,
Southwest Florida Water Management District

The current high water is not isolated to the Withlacoochee River system.

The Peace, Myakka, Manatee, Alafia and Hillsborough Rivers (within our District) have already reached flood stage.

Flooding is also occurring in numerous low-lying areas near wetlands, swamps or other generally low areas throughout our 16-county region. This high water is a natural response to the rainfall our region has been receiving. Please take the necessary precautions to protect yourselves and your property, because its only mid-August and more rain is on the way.

Rainfall:

  • The National Weather Service is predicting heavy rainfall across our region through the weekend and our area is under a flood watch.
  • Our region’s soils are already saturated, swamps are full, and water levels are up due to above average rainfall over the past several months.
  • Additional high rainfall has the potential to cause flooding along rivers and lakes or in other low-lying areas.

Withlacoochee River:

  • River flows and water levels continue to rise in response to recent rains.
  • The Green Swamp is saturated and flows downriver are increasing.
  • Forecasted rainfall this week is expected to raise water levels on the Withlacoochee River to near flood stage.
  • You can follow changing NOAA forecasts for several locations along the river by clicking this link: https://www.weather.gov/serfc/ from NOAA’s Southeast River Forecast Center.

Little Withlacoochee River:

  • Over the past couple weeks, flooding has already occurred along the Little Withlacoochee River, due to localized heavy rainfall in early August.
  • Although levels had dropped over the past week, they are beginning to rise again from recent rainfall over the past couple days.
  • There are no structures in the Green Swamp that can control flow in the Little Withlacoochee and additional rainfall will continue to naturally raise river levels.

Tsala Apopka Chain-of-Lakes:

  • Rainfall has single-handedly raised lake levels again this year.
  • Structures are normally opened to bring water into the lakes, but this year they’ve been open to release water from the lakes.
  • The Floral City Pool is currently about 8 inches below high guidance level. The Inverness and Hernando Pools are 1.5 and 4 inches lower, respectively.
  • Today, the Brogden Bridge (Turner Camp Rd) and S-353 structures were opened to release water from the Inverness and Hernando Pools, respectively.
  • Our structures staff are closely monitoring water levels and will continue to operate structures to maintain storage in the lakes, because additional rainfall is expected.
  • Keep in mind that most of these are water conservation structures and many times flow out of a lake is counteracted by additional rainfall on that lake.
  • The attached map shows these three pools and the structures/canals that connect them between each other and the Withlacoochee River.

Lake Panasoffkee:

  • Water levels on Lake Panasoffkee, which are very high for this time of year, are still rising as rainfall continues to fill the aquifer and sustain high inflows from the surrounding creeks.
  • The lake is now 6 inches higher than it peaked after Hurricane Irma (2017) and only 9 inches lower than the flooding that occurred from the 2004 hurricanes.
  • The Wysong Structure has been fully lowered for the past couple weeks and has had no impact on lake levels.
  • There are no additional structures on the Withlacoochee River that are impacting water levels on Lake Panasoffkee.
  • Outflow from the lake to the Withlacoochee has not kept up with inflow, which is normal for this time of year, and the lake is expected to continue to rise.
  • Dense amounts of hydrilla (invasive vegetation) which have grown in the Outlet River this summer may be limiting outflows.
  • To address this, FWC and SWFWMD are coordinating a treatment next week to remove the hydrilla, and hopefully increase flows from the lake.
  • See the news release that was sent out today: https://content.govdelivery.com/accounts/FLSWFWMD/bulletins/258c30c

Lake Rousseau and the Lower Withlacoochee River:

  • Inflows to Lake Rousseau continue to rise as flows in both the Withlacoochee and Rainbow Rivers increase.
  • Outflow from the lake to the Lower Withlacoochee River has been maxed since June.
  • The Inglis Main Dam remains open, diverting excess river flows to the Barge Canal.
  • Lake Rousseau has been lowered a few inches to help keep water levels lower at Dunnellon.
  • The structures on Lake Rousseau can only impact river levels upstream through Dunnellon, but during higher water times, that impact is minimal.

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