SFWMD managers battle severe drought
SFL Weekly Watersheds Summary: April 2 – 8

WEATHER. As we continue our descent deeper into this year’s heart of the dryness, its worthwhile pointing out that this year’s swing back into severe drought management conditions (reminiscint of 2001) is actually the culmination of 3 consecutive seasons of below-average rainfall. It was just 18 months ago that Wilma flushed the system full of water at the tail end of a very rainy 2005 wet season. But as the pendulum swings in SFL — the wettest hour is always just before the next drought begins. Wilma’s drenching has been followed by consecutive dry, wet, and dry seasons of below-average rain. In the 18-months that have elapsed since Wilma’s passing in November 2005, the Big Cypress area has received only 55 inches of rain. Stunningly, the preserve received 52 inches in the 6-months prior to Wilma alone. Over the past 10 years, the preserve has averaged 68 inches of rain over consecutive 18-month dry-wet-dry season periods. And the Big Cypress has been one of the wettest areas of the District over the past 18 months. Conditions are even more severe in the Kissimmee Valley and Lake O where only around 40 inches of rain have fallen since Wilma passed through. Again, these numbers are very similar to the 18-month period that led up to severe drought conditions in Spring of 2001. What’s interesting is that we started off this year’s dry season thinking that a burgeoning El Nino would wetten the winter outlook. Obviously that never happened. In 2001 the climatic backstory was the unexpected La Nina that dessicated south Florida’s summer rain machine for most of the 2000 rainy season — and which unserendipitously arrived on the heals of the water management community’s decision to artificially lower Lake O for ecological reasons. This year’s drydown has been more or less naturally ET driven process in comparison, and lack of inflows from the Kissimmee. Suffice it to say that the weather pendulum has once again swung to an extreme, this time in the dry direction. The obvious fix is to get it swinging back in the other direction with some rain. Hopefully an early and abundant wet season is on the way.

BIG CYPRESS. Preserve-wide stage has been tracking at a new 5-year low for the past month. Preserve-wide stage is 1.5 ft below our 5-year average for mid April, and about 8 inches below middle April of last year. Even the remnants of surface water in the southeast corner of the preserve have begun to vanish. The clock continues 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 already been dry for over 3 months with a solid 2 months, if not 3, before those scenic vistas start reflooding in mid June.

EVERGLADES. Regulatory stage in 3A is about a foot lower than mid April of last year, and also about a foot below the 5-year average for mid April. There is still about a foot deep of water in the sloughs of southern 3A, but sloughs in 3A north of I75 are dry, as are the sloughs in WCA 2. Down in the Park, water depths of a few inches are hanging on in the central parts of Shark River Slough. Loxahatchee is also showing water depths of around a few inches in its sloughs (at Site 1-7 and Site 1-9); but keep in mind that these sloughs typically hold water all year round. This year they appear to stand a good chance of going dry. Gates have been closed in all parts of the Everglades plumbing system to mitigate drought effects. Historically speaking, water depth in southern 3A is at a very similar level to mid April of 2001 — the biggest drought of recent memory — but current water depth in southern 3A is still a foot higher than the early April’s of 1989, 1990, and 1991 when severe drydowns plagued that area.

LAKE O. As of Sunday, Lake O stage stood at 10.09 ft msl. Current Lake O stage is over 4 ft below mid April of last year and the 5-year average for mid April. Lake stage has dropped about 2 ft since the end of December and over 3 ft since this year’s September high-water mark of 13.5 ft msl. Historically speaking, current lake stage is tracking at the same level of mid April 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 has now dropped below the magic number of 10.2 ft msl, below which forward pumps are required to feed water through water control structures in order to meet downstream water supply obligations. The District has installed 100 cfs pumps is the bays of S-351 (6 units) and S-352 (4 units) and will be installing at S-354 this week (4 units) for that reason. Lake stage has now been below the bottom of the Lake’s interior-levee marsh (13.5 msl) since middle April of last year (12 months).

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