Withlacoochee River System Update - 5/1/2023

Recent Rainfall Temporarily Halts Declining Water Levels

 

Rainfall:

• After a very dry start to the year, we’ve finally experienced some decent rain showers in recent days.
• Our region received about 2.5 inches of rain last month, close to the historical average for April (2.8 inches).
• These recent rains have been a welcome sight, but we’re still playing catch up in 2023.
• So far this year (January through April) our region has received just 5.8 inches of rain, less than half the historical average (12.3 inches) for the first four months of the year.
• Region-wide aquifer (groundwater) levels are currently in the 40^th percentile, below average, and much lower than they were a year ago (82^nd percentile).
• Our wet season begins in June, and historically May can be very dry or very wet.
• If the recent rainfall trends continue, we could see our water resources start to bounce back.
• But, if this next month is hot/dry, water levels and flows could continue the sharp declines we saw from January through March.

 

 

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

• The Withlacoochee River had been dropping sharply in recent months due to the lack of rainfall throughout the region.
• Increased rains over the past couple weeks have temporarily halted that downward trend.
• River levels and flows are essentially back to where they were a month ago thanks to decent rainfall in recent days, resulting in very little net change over the month of April.
• We could see the downward trend pick up again in May, unless our region continues to receive significant rainfall.
• Water levels along the Withlacoochee River remain about 1-2 feet lower than they were a year ago.
• River flows are 73% lower than they were last year at this time.
• There is currently no measurable flow leaving the Green Swamp (beginning of the river) and the recent rains aren’t expected to make a lasting difference on river conditions.

 

 

The Withlacoochee River near Halpata Preserve in Marion County (April 2023)

 

 

Tsala Apopka Chain of Lakes:

• If you live along the Tsala Apopka Chain of Lakes in Citrus County, you’ve noticed lower water levels this spring.
• In fact, lake levels are about 17 inches lower than they were this time last year.
• The reason is significantly less rainfall this year.
• The lakes, canals and marsh areas rely on rainfall and when it’s scarce, water levels will naturally decline.
• All three pools of the Tsala Apopka Lake Chain dropped about 5 inches in April…
• …and if it weren’t for the rainfall last week, water levels would be even lower.
• The Withlacoochee River remains lower than the lakes, and river inflows won’t likely occur again until sometime this summer.
• The water control structures, aka “locks”, which were closed in early November, remain closed helping to conserve water in the lake chain.
• Concrete repairs are continuing at the S-353 structure so that it will be operational again for this upcoming wet season.

 

Concrete Repairs Continue at the Tsala Apopka Outfall Structure (S-353)

 

 

Lake Panasoffkee and Wysong:

• Rainfall is also important to Lake Panasoffkee.
• Water levels rise when rain falls directly on the lake and when flows to the lake increase from higher aquifer levels (indirect result of rainfall).
• Water also naturally flows out of the lake into the Withlacoochee River.
• This year, Lake Panasoffkee water levels have dropped lower than we’ve seen in 6 years (since 2017), due to minimal rainfall in recent months.
• Flows into and out of Lake Panasoffkee are also currently much lower than they were a year ago.
• Flow in the Withlacoochee River is only a fraction of what it was last year at this time.
• When the Withlacoochee River is low, the Wysong Structure helps to limit how fast water can exit Lake Panasoffkee, but it cannot keep lake levels from dropping if rainfall is scarce.
• The 230-foot-wide main gate at Wysong remains fully raised, while the 19-foot-wide independent gate is partially raised.
• Even with recent rains and the help of Wysong, Lake Panasoffkee water levels fell another 2 inches in April and are currently about 14 inches lower than they were 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.
• Lake Rousseau water levels don’t typically fluctuate much, except during periods of very high or low flows along the Withlacoochee River upstream.
• In April, as river flows declined to some of the lowest levels we’ve seen in several years, Lake Rousseau also began dropping.
• Over the past month, Lake Rousseau water levels fell between 3 to 6 inches, with the latter amount occurring closer to Dunnellon.
• Recent rains have slighted boosted water levels, but if those rains don’t continue, we could see Lake Rousseau drop further.
• Overall, inflows to Lake Rousseau are about 45% lower than they were a year ago.

 

• The primary outlet from Lake Rousseau is through the Inglis Bypass Spillway to the Lower Withlacoochee River (see maps below).
• The Inglis Main Dam, which discharges excess flows to the Barge Canal, was closed in early January and remains closed.
• All flow is still passing downstream through the Bypass Spillway, which is currently flowing at about 41% of its capacity.
• Less rainfall in recent months has also resulted in about 58% less flow exiting Lake Rousseau to the Lower Withlacoochee River, as compared to a year ago.

 

Hope you have a wonderful week!

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