First half of October dry so far
SFL Weekly Watersheds Summary: Oct 2 – 8

Big Cypress NP. October has been pretty rainless in the Big Cypress to date, as it has been throughout the rest of South Florida. If that trend continues it could give us a head start to the upcoming Dry Season. October can be a pivotal rainfall month by merit of its hit-or-miss nature. The presence or absence of tropical storms tends to be the difference maker; either turning October into the final wet-season month, as it did in 1995, 1999, and 2005, or else front-ending the impending dry season with an additional 2-4 weeks of low rainfall, as it did in 2003 and 2004. Last year’s October took the former path. It was bookended by steady rainfall accumulations in the first part of the month, followed by a mid-month dry spell, and then bookended with an exclamation point of 3-5 inches from Wilma; adding up to a October 2005 rainfall total of 8 inches, and a 2005 wet season rainfall total of 53 inches. This year’s October in the Big Cypress has been rainless so far, and the current 2006 wet season total is tracking at 42 inches (since the start of May). Wetland water stage has already dropped down about a half foot from this year’s September high water mark. Preserve-wide water stage has dropped down into the hydric pinelands, with wet prairies, tall cypress, and swamp forest remaining flooded with water.

Lake O. Lake stage is at 13.2 ft msl, dropping about a third of a foot from its post-Ernesto high water mark in mid-September, which now places it slightly below the bottom of the Lake’s interior-levee littoral zone. Structural inflows and outflows from the Lake were fairly neglible for the week. The spike of freshwater that discharged through the S79 as a result of +10 inches of rainfall on the East Caloosahatchee Basin in late August has come to an end. Over the past 5 years, freshwater discharge through the S79 and S80 have averaged 5k and 2k cfs, respectively, for the month of October. This October’s lack of flow through those structures is largely the result of Lake stage being around 2.5 ft below the 5-yr average October stage and low rainfall in the Kissimmee and the Istokpoga watersheds over the past couple weeks.

Everglades. The S10s are closed, and are currently pooling water +3.5 ft higher in Loxahatchee than in the downstream WCA2. The S11s were closed this week, and are currently pooling water 1.5 ft higher in WCA2 than in the downstream WCA3A. Of interest, water stage at Site 63 (just downstream of S11s) has dropped about a half foot since late September, whereas further downstream in 3A (at Sites 64 and 65) water levels have only dropped an inch or so. Water levels in 3B (Site 71) have risen a few inches over the same period. Discharge through the S12s peaked at around 2,500 cfs in late September, and is now flowing at a combined rate of 2,000 cfs, which is around 1,000 cfs below October’s 5-yr average flow rate for the S12s. Water levels in southern 3A are their lowest mid-October level since October 2002. In the big picture, October water depths in southern 3A have been consistently deeper since 1990, after which they have routinely exceed a 3 ft depth. In comparison, the October high-water mark throughout the 1970s and 1980s only very rarely exceeded a 3-ft water depth (as occurred in October 1976 and October 1983). Total inflows under US41 into Everglades National Park are now evenly split between its headwater preserve (2k cfs) — feeding the Park’s western arm — and the S12s (2k cfs) — discharging into the western banks of Shark River Slough — for a total inflow rate of around 4k cfs.

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