Dry season puts another month in the books
SFL Weekly Watersheds Summary: March 26 to April 1

WEATHER. For historical book-keeping purposes, I calculate as the dry season as spanning the 6-month period from the beginning of November to the end of April. That means with March now in the books, we have only one month remaining on this year’s dry season. Keep in mind that just like a wet October can add a month to the end of the wet season, the same regularly occurs for the first couple weeks of May until summer rains start in earnest. For the Big Cypress area, May has averaged around 4 inches of rain over the past 10 years, in comparison to under 2 inches for the core dry season months and over 8 inches for the core wet season months. But the bulk of May’s 4 inches can fall toward the end of the month when the rain machine starts reving up. Anyhow, we are entering the nadir of our driest several weeks of the year — which will likely extend for some distance into May — on the low end of the spectrum. Since the start of November we’ve received around 6 inches of rain. At the beginning of April last year we had received a similar paltry 5 inches of dry-season rain. Our 10-year average for the first 5 months of the dry season has been 10 inches. In the El-Nino stoked dry season of 1997-1998 we received a whopping 22 inches for the first 5 months of the dry season.

BIG CYPRESS. Preserve-wide stage has been tracking at a new 5-year low for the past 4 weeks. Preserve-wide stage is 8 inches below April 1st of last year and 11 inches below the 5-year average for the start of April. The wetting front has pretty much full evaporated from the preserve’s surficial wetlands and descended into the top of the aquifer other than in the preserve’s southeast corner where surface water is still hanging around in its marshes and central sloughs. The clock has started to tick on how long the drydown for the preserve’s various wetland types will last this year. Back in the dry season of 2000-2001 the drydown for the preserve’s wet prairies lasted for 7.5 months. That was our driest year in recent memory. This year, the preserve’s wet prairies have been dry for 3 months with 2-3 months to go before they are predicted to rewet in mid June. But there’s no telling in any exactitude when the late spring sun will start cooking up rain worthy cloud masses.

EVERGLADES. Regulatory stage in 3A is about 8 inches below both the start of last year’s April and the 5-year average for the start of April. Historically speaking, regulatory stage in 3A is at a very similar level to early April of 2001 — the biggest drought of recent memory — but current 3A stage is still over a foot higher than the early April’s of 1989, 1990, and 1991 when severe drydowns plagued that area. Down in the Park, surface water stage at P33 has been just barely tracking at a new 5-year low for the past half year now, since the end of the meteorologic wet season. Slough depths at P33 are recording at below 0.5 ft deep in comparison to a 1.5 ft deep slough depth just north of US41 in 3A. Farther north in Loxahatchee, water depths at its interior sites (Sites 1-7 and 1-9) are showing 6-8 inches of water still in its sloughs. Keep in mind that sloughs typically hold surface water all year round in Loxahatchee, where sloughs in WCA 2 and northern 3A go dry in the spring.

LAKE O. As of Sunday, Lake O stage stood at 10.39 ft msl. Current Lake O stage is just around 4 ft below the start of last April and the 5-year average for the beginning of April. Lake stage has dropped about 1.5 ft since the end of December and 3 ft since September. Historically speaking, current lake stage is about 2 inches higher than April 1st of the Lake’s record plunge during the 2001 drought year. Lake stage bottomed out at 9 ft msl in late May of that year. Lake stage is approaching the magic number of 10.2 ft msl, below which forward pumps will be required to feed water through water control structures in order to meet downstream water supply obligations. Lake stage has now been below the bottom of the Lake’s interior-levee marsh (13.5 msl) since middle April of last year (almost 12 months).

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