Lake rises above 9 ft

SFWJ: July 2 – 8.
Lake rebounds above 9 ft

Rainfall. Lake Okeechobee’s rise back above 9 ft msl was the hydrologic story of the week. Back in late May water managers had speculated on the possiblity of Lake stage dropping below 8 ft msl before summer rains kicked in. Fortunately, that worst-case scenario never materialized. Instead, Lake O dipped only very shallowly below the 9 ft benchmark, even though the Lake only received 5.5 inches of June rain — 2 inches below its long-term June average — and inflows from the Kissimmee still have not begun. Even more fortunately, meteorological predictions for sea-breeze fed storms over the Lake and Upper East Coast did materialize this past week. Those storms brought a long-awaited weekly deluge of 4 inches over the Lake, Lower Kissimmee, Palm Beach Coast, and Martin-St Lucie. East Caloosahatchee Basin led all other basins with 5 inches. District-wide, that made last week the rainiest week of the rainy season to date, chiming in at just above 3 inches of rain District wide. The last time we had a 3-plus inch weekly rain total was last September 2006 in the wake of Ernesto when 4-plus inches of weekly rain fell District-wide. The tables were switched on that one: the majority of Ernesto’s rain fell on the District’s southwest Corner.


How did this year’s Lake plunge compare to recent years. Although this year’s lake stage bottomed out at a slightly lower low-water mark than 2001, dropping a few inches below the 9 ft barrier for a full month in comparison to 2001’s momentary touchdown below 9 ft to 8.97 ft, Lake stage as late as March 2001 was tracking over a half foot lower than March of this year. A year ago today, Lake stage was 3 ft higher at 12 ft msl (see above).

Big Cypress: Big Cypress National Preserve ,Corkscrew and OK Slough . The rise of preserve-wide stage has hit a mid-season snag. Steady rains in early June had our preserve-wide stage rising in tune with our 5-year average, but a drop in rainfall has caused the wetland wetting front to retreat back into the tall cypress. Currently, preserve-wide stage is tracking about 9 inches below the 5-year early July average, and about 9 inches below early July of last year.

Everglades: Everglades National Park ,WCA3,WCA12. Headwater flows are entering Everglades National Park through the S12D and S333; the later of which feeds water into the L29 feeder canal that discharges water into the Park’s northeast Shark River Slough. Flow rates through both structures are small at this point, both totaling under 50 cfs. The rest of the S12s will be sequentially opened starting July 15th in accordance with the rainfall plan for delivering flows to the park. The rainfall plan was first developed in 1985 as an interim measure to find ways to re-introduce headwater flows into the Park’s northeast Shark River Slough with the caveat of not causing flooding concerns in residential and agricultural lands on the unprotected east side of the urban east coast L31 Levee. That plan remains in effect today as part of the Interim Operations Plan, with similar interim measures being applied for routing water into Shark River Slough’s smaller eastern counterpart Taylor Slough. Over the past 5 years, the S12s typically peak in October with a combined flow rate of around 3000 cfs. However, last year S12 flows did not rise above 1500 cfs until September, and did not exceed a weekly average of 3000 cfs all year. The year before that (in 2005) the S12s flowed at 3000-plus cfs for 4 consecutive months, briefly peaking at 4500 cfs. But its 1994-1995 that tops the charts with 5 consectutive months of 3000-plus cfs, peaking at 7000-plus cfs in January 1994. The S332s (B,C,D) have been releasing water into the Park’s Taylor Slough headwater wetlands since mid June, and are currently flowing at around 500 cfs.

Slough water depths in southern Water Conservation Area 3A have rebounded back to a 1.5 ft depth. That’s the same depth as mid-July of last year. Sloughs in northeast 3A, downstream of the S11s, have been dry now for 4 consecutive months. Just upstream across the levee in Water Conservation Area 2A, water is currently pooling up 2.5 ft behind the S11s, where sloughs are flooding at a 1.5 ft depth. However, slough water depths in 2A’s interior are shallower (0-0.5 ft deep), indicating that canals are stacking water up against the S11s. This is supported by review of regulatory stage levels in 2B showing a current stage of 8 inches below the 5-yr early July average, and at the same level as early July of last year.

Regulatory stage in Loxahatchee is tracking in unison with both the 5-yr average for early July and early July of last year. That places slough water depths at just under a foot, which means that the edges of the wetting front are rising up into the slough’s slightly higher ridge counterparts.

Lake O: Lake O ,Kissimmee . Since the start of the new millenium, lake levels have fluctuated widely: covering a 9 ft range from its high to low-water extremes. Numbers in that range to remember (in ft msl): 8.8 ft: historic low-water mark, 10 ft: elevation below which lake’s southern gates do not gravity feed, 13.5 ft: bottom elevation of lake’s interior-levee marshes, 15.5 ft: elevation above which lake’s interior-levee marshes are flooded, 17 ft: elevation above which levee integrity becomes jeoparidized, 20 ft: approximate elevation above which lake spilled over southern rim into the historic Everglades.

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