Demise of sheet and flow conditions in Big Cypress
SFL Weekly Watersheds Summary: Nov 13-20

RAINFALL. Dry conditions continue to prevail across south Florida. The past year has been a dry one relative to historic standards. All major basins have received less than 50 inches over the past 365 days, with the northern basins of the KOE system receiving less than 35 inches over past 365 days. To put that in perspective, over the past 5 years the Big Cypress and Southwest Coast basins have averaged around 50 inches in the wet season alone (May through Oct). Our most recent wet season was particularly dry for the northern-most basins in the KOE system. Less than 25 inches fell on Lake O and the Kissimmee River this wet season, which is about 10-15 inches below the average of the previous 5 wet season rainfall total for those basins. Southwest Florida and Big Cypress received around 42 inches of wet season rain in comparison, which is 7 inches below the 50 inches of wet season rain we’ve averaged over the past 5 years. This year’s rainless start to the rainy season hasn’t helped out matters. ENSOs upswing into an El Nino phase is anticipated to amplify dry season totals, but that hasn’t registered yet in our rain buckets.

BIG CYPRESS. Sheetflow is lossing both its “sheet” and “flow” status. Sheetflow conditions prevail in the preserve when there is a widespread presence of surface water at or above the wet prairie landscape type (forming more or less a continuous and shallow sheet of water), and the slow and steady downhill flow of this shallow water body towards the 10000 Island estuaries. The summer’s sheetflow regim has dropped down a notch to a patchy standing water regime where surface water are still present (in tall cypress, swamp forest, and marsh landscape types), … but are largely unconnected with one another and are no longer flowing. Flows under US41 have dropped to near zero. In comparison, last Thanksgiving nearly 4000 cfs were still flowing under the Trail in the wake of Wilma, … which also matches this year’s 4000 cfs peak US41 flow in September following Ernesto.

EVERGLADES. Interestingly, water depths in southern 3A have stayed steady (at 2.66 ft deep) since the start of November wherease during the same 3-week time period water depths farther upstream in 3A (at Sites 64 and 63) have dropped about a third of a foot. This difference in hydrologic response is caused by the recent closing and reduction of flows through the S12s, … which has causes water depths to pool at the southern end of 3A. About a combined 400 cfs are still flowing through the S12 C and D, … and around 300 cfs is being released down the S333 towards NE Shark River Slough culverts. In comparison, close to 3000 cfs were still flowing through the S12s November a year ago. This year’s low and early demis of wet season flows through the S12s is similar to 2002 and 2000. Also of interest, in the two months since Ernesto passed, water depths in northern 3A have dropped from 3 ft deep to 1.3 feet today. In comparison, water depths in southern 3A have only dropped a third of a foot from 3 ft deep to 2.66 ft today over the same time period.

LAKE O. Lake Okeechobee stage is currently at 12.39 ft msl. That places it 3 ft below the average stage for the past 5 Thanksgivings, 4 ft below Thanksgiving of last year, and 0.7 ft higher than Thanksgiving of the 2000 drought year. Incidently, Lake stage has been greater than 16 ft msl for the past 3 Thanksgivings, … and during Thanksgivings of 1994, 1995, and 1999 Lake stage was greater than 17 ft msl.

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