Big Cypress National Preserve enters heart of dry season.
SFL Weekly Watersheds Summary: March 5 – 11
WEATHER. The first third of March has been rainless district-wide. March has actually been the rainiest of our six dry season months in recent years. Over the past 10 years the preserve has averaged 2.7 inches of rain in March. Our next highest dry season month is November at 2.4 inches (but that number is skewed by the 10 inches of November rain from Mitch in 1998) and April at 2.2 inches. In comparison, all the other dry season months are under 2 inches. Our rainiest Marches of recent past were in 2004 and 1997 when approximately 5 inches were recorded in those years. Like much of last year’s dry season, last March was a dry one, with only 0.3 inches falling. In terms of the big “dry season” rainfall picture, the preserve has received around 5.3 inches to date (from Nov 1 to present). Last year we had 5.3 inches over the same time period, but don’t forget that last year water levels got a late wet-season last hurrah from Wilma. This year our wet-season fizzled out early, launching us into the dry season mode a month early in early October.
BIG CYPRESS. Preserve-wide water levels have officially dropped below the swamp forest (and marsh) wetland landscape type. Our swamp forest and marsh wetlands are the first to wet at the onset of the wet season and the last to go dry at the back end of the dry season. This year the swamp forest and marsh wetlands held water for almost 9 consecutive months. In comparison, last year was slightly wetter, holding water in our swamp forest and marsh habitats for 10 months. The shortest season of swamp forest flooding in recent memory was the drought year of 2000-2001 when the preserve’s swamp forest and marsh wetlands only held water for 7 months. Some years the swamp forest and marsh habitats hold water all year round. That condition most recently occurred from June 2003 to May 2004 when the preserve’s swamp forest and marsh wetlands remained flooded for a whopping 23 consecutive months, or almost 2 years straight. But usually there’s a couple month dry down period in the late winter and spring where even for our deepest wetlands. That’s where we’re at now.
The drop of preserve-wide water levels below the swamp forest and marsh wetland communities marks an important milestone in the annual water cycle of the preserve. Water will increasingly become a scarce resource in the ecosystem, leaving only the deepest holes of natural refugia (plus our canals and borrow pits) with water. Water levels have also reached an inflection point where they have begun to drop more precipitously and will continue to do so for the remainder of the dry season. For example, preserve-wide stage dropped about 4 inches per month for the first 5 months of the dry season. However, for the remainder of the dry season (barring significant rains) the drop in water levels will accelerate to around 12 inches per month due to a combination of increased evapotranspiration and the physical displacement of the water surface into the top of the aquifer. Suffice it to say we’ve entered into the heart of the dry season that won’t reach its bottom or slow in its descent until the rainy season heats back up.
Keep in mind that its not uniformly dry in all parts of the preserve. The southeast corner remains the wettest. That area is still holding water at the tall cypress and slough wetland communities.
TURNER RIVER. Sadly, the Turner River stage has dropped to the point where it is no longer navigable to its tailwaters. River stage is too low to paddle a canoe through the first set of mangrove tunnels. The entire river length was navigable this year for a 5-month period from mid October (when river stage first dropped low enough to fit canoes and kayaks between the water surface and top of the mangrove tunnels) to early March (when river stage became too shallow in the mangrove tunnels). River depth is still slightly above 1 ft deep at the US41 bridge, so its still possible to paddle the quarter mile upstream to the river’s famed headwater pools. But even that stretch will be too shallow to paddle in just a few weeks. Turner River is currently around 7 inches lower than middle March of last year and 7 inches below the 5-year mid March average.