Water Log 7/29

Flows resume in Kissimmee
Week of July 23-29

Lake Okeechobee continues to dominate the news reels. After a nine-month hiatus, flows into the Lake from the Kissimmee River have resumed. During a normal year, the Kissimmee accounts for around a quarter of the Lake’s inflow. Inflows from the Kissimmee grounded to zero in October 2006, having previously flown more or less continuously into the lake 365 days per year from July 2001 to October 2006. Flow in the Kissimmee is an important criteria for maintaining the ecological health in the river. It helps boost dissolved oxygen (DO) levels in the river channel (DO levels below 2 mg/L are a concern) and also keeps algal blooms in check.

So it’s good to have flow back in the river. Last week’s average flow rate through the Kissimmee’s southernmost lock before it spills into the Lake (S65E) was around 1300 cfs. Last summer, discharge through the Kissimmee’s S65E peaked at just over 3000 cfs in September following the wake of Ernesto, but other than that brief spike in flow, one has to go back in time 17 months to March 2006 when Kissimmee inflows to the Lake consistently stayed above the 1000 cfs mark. In the water-drenched summer of 2005, weekly-averaged inflows through the S65E touched up above 10,000 cfs in July (following a wet June) and early November (following Wilma).

As of Sunday, Lake stage had nosed up to almost 9.2 ft msl. In comparison, during the most recent comparable drought year of 2001, Lake stage was around 10.5 ft msl at the end of July, and rose above 11 ft msl during the first week of August of that year.

Big Cypress: Big Cypress National Preserve ,Corkscrew and OK Slough . Preserve-wide stage is tracking right at the 5-yr average for late July, and also tracking at a similar level as late July of last year. That puts the wetting front well up into the preserve’s wet prairies and at the base of our hydric pineland communities. If you’re a coastal dweller traveling through the preserve by car, the southern half of the preserve by US41 remains about 4 inches higher than wetland water depths along I75 to the north. Just a few weeks ago in mid July wetland water depths were a foot higher in the south than the north. That means that wetland water depths in the north have risen a half foot over the past 2-3 weeks, while water levels in the south have pretty much held steady. The northwest corner of the preserve fed by Okaloacoochee Slough remains perplexingly dry compared to rest of the preserve. Wetland stage has yet to break above ground surface even in the deeper slough communities.

Everglades: Everglades National Park ,WCA3,WCA12. Regulatory stage in Water Conservation Area 3A is still low, keeping the S12s — the main outlet gates for releasing freshwater flows in Everglades National Park — closed. 3A’s regulatory stage — one of the primary guidance tools that water managers use to determine flows from 3A — is calculated as an average stage from three hydrologic monitoring stations: Site 65 (near US41), Site 64 (US41-I75 midpoint), and Site 63 (north of I75 near S11s). 3A’s current regulatory stage just nosed up above 9 ft msl. That puts this current year a month behind last year’s late-June rise above the 9 ft threshold. The year prior, in 2005, 3A regulatory stage never dropped below 9 ft, even during the spring dry down. During the drought year of 2001, 3A stage was already above 10 ft by late July. By any measure, 3A stage is currently on the low-end of the spectrum, thus explaining the absence of flows through the S12s.

The good news is that freshwater flows continue to feed into the western arm of the Park courtesy of the Park’s friendly headwater preserve (Big Cypress National Preserve). Freshwater flows have been discharging through the bridges that underlie the Tamiami Trail, from Carnestown to 40 Mile Bend at 500 cfs for the past month and a half. That’s about 1500 cfs short of the 5 year late July average. Over half of the 500 cfs flow through 4 consecutive bridges on the preserve’s western end that feed water into Turner River and Barnes Strand. The main Barnes Strand Bridge (Bridge #86) accounts for 30 percent of the flow across the 30 stretch of US41, and leads all other US41 structures (including the S12s) for moving water south across the Trail. Way to go Bridge 86! Your the unsung hero of getting flows into the Park.

Water is also moving into the Park from the S332s that feed water into Taylor Slough’s headwaters, at a weekly-averaged rate of around 4oo cfs. Discharges of this magnitude have been flowing on and off since late June.

If your driving along US41 through the Everglades, around a foot of water is pooling behind the S12s. If you take the detour down to Shark River Tower, wetlands are holding around 8 inches of water. As far as the eye can see to the east, in central Shark River Slough (at P33), water depths are twice as deep (1.3 ft deep), but even that’s a few inches below the 5-yr late-July average of 1.6 ft deep. Farther to the northeast, in the Park’s headwater portion of Shark River Slough, slough water depths are several inches shallower at around 0.75 ft deep, due in part to lack of inflow under US41 through the L29 culverts. Water levels will remain seasonally low until we get more water directly from rain, or headwater releases from the north.

If you take Hwy 27 towards Belle Glade, over 3ft of water is pooling behind the S11s. Those gates remain closed, as they have been since October 2006. Slough water depth in downstream Site 63 has finally reflooded with a few inches of water. Assuming water stays above surface for the upcoming weeks, and/or the S11s open soon, that puts this year’s spring drydown at Site 63 at 4.5 months. The previous year only had a 2 month spring drydown in the sloughs as Site 63, with continuous flooding occurring for all of 2005. In the Everglades’ Northeast corner in WCA1 (Loxahatchee NWR), the S10 outlet gates are also closed. Over 3.5 ft of water is currently pooling up behind the S10s. That means the wetland wetting front has risen above the slough and ridge landscape, into the bayhead zone in southern Loxahatchee, but farther north in central Loxahatchee at Site 1-7, the wetting front is a notch lower, still hanging around in the ridge landscape communities.

Lake Okeechobee: Lake O ,Kissimmee. Other news with the Lake are minor discharges of around 400 cfs being discharged down the Caloosahatchee through the S79 WP Franklin lock. The S79 was maintained at a no flow condition through the spring as a result of the drought, but has been discharging at a few hundred cfs sporadically in June, and more continuously in July. Average weekly flows into the lower St Lucie through the S80 have remained below 20 cfs for the past 4 months since the start of April, and has not discharged over 1000 cfs in a sustained pattern since December 2005. Currently, reverse flows are backflowing into the Lake at St Lucie’s Port Mayaca lock (S308), L8 Canal Point lock, and the upper Caloosahatchee’s S77 Moore Haven lock.

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