M E M O R A N D U M

 

TO:                 Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:            SFWMD Staff Environmental Advisory Team

 

DATE:            September 2, 2008

 

SUBJECT:     Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

Overall the Central and Southern Florida system continues to recover from rainfall associated with Tropical Storm Fay.  During the past week, inflows from the tributary basins have begun to taper off but remain in the very wet tributary hydrologic conditions.   Stages in Lake Okeechobee (Lake) have risen to within one foot of the intermediate band, which calls for discharges of up to 4000 cfs at S-77 and up to 1800 cfs at S-80.  The United States Army Corps of Engineers (USACE) indicated that the current volumes and anticipated duration of local runoff would be factored in to their discharge decision.  The District scientist have conducted site visits to monitoring stations within Lake Okeechobee and have indicated that the very rapid rise in Lake stages are impacting the Lake ecology.

 

Background

 

Drier conditions Tuesday, and Wednesday; followed by storms on Thursday.  Hurricane Gustav is spinning down over Louisiana and Tropical Storm Hanna is near the southeastern Bahamas.  Sinking air between the two systems should suppress shower development over the District the next couple of days.  Northeast winds will focus a few showers east as well as southwest each day.  Tropical Storm Hanna is forecast to track close to the eastern edge of the Bahamas and strengthen to Tuesday and Wednesday.  As Hanna moves through the northern Bahamas Thursday, winds and shower activity will increase over the District with possible Tropical Storm Conditions north and east.  A trailing trough will keep showers and thunderstorms mainly north and east Friday.  The next ten days precipitation outlook is near average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received approximately 1.5 inches of rainfall and the lower basin received approximately 1.7 inches (Seven Day Raindar Estimate 8/26/08 – 9/02/08).

 

Water levels in all of the upper basin lakes are at or slightly above their regulation schedules.  Releases are being made from Lake Myrtle (150 cfs), Lake Hart (415 cfs), East Lake Tohopekaliga (735 cfs), Lake Tohopekaliga (2,099 cfs), the Alligator Chain (399 cfs) and Lake Gentry (551 cfs).  Discharge from Lake Kissimmee is currently 7,272 cfs and discharge at S65C is 10,925 cfs.

 

Water depths on the floodplain within the restoration project have decreased by about 0.5 feet over the last week and currently range from 1.0 – 7.7 feet.  The floodplain in the restored reach is completely inundated at this time.

 

From 8/26/08 to 9/02/08 dissolved oxygen (DO) concentrations in the Kissimmee River ranged from 0.1 mg/L to 1.5 mg/L and averaged 0.5 mg/L.  DO concentrations are still below levels of concern, however, the overall trend shows a slight increase over the last few days.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 14.60’ NGVD, which is 0.97’ higher than a week ago, 3.69’ higher than a month ago, and 4.10’ higher than it was a year ago.  The current stage is 0.35’ above the historical average for this date, and 1.36’ above the simulated historical average for the current regulation schedule (LORS2008).

Total reported inflows are 19324 cfs, with contributions from the Kissimmee River (11895 cfs), S84 (1235 cfs), S71 (2287 cfs), S72 (781 cfs), S191 (1100 cfs), Fisheating Creek (1261 cfs),

and the L8 at canal point (485 cfs).  Back pumping from the EAA is occurring through S4 at 235 cfs.  Outflows of 265 are reported through S154.  No flow data are available for the S77 or S308.

 

Last week, field crews re-sampled 74 of the 154 annual mapping grid cells that had Submerged Aquatic Vegetation (SAV) prior to Tropical Storm Fay.  Plants were still present at all but three cells.  These three cells had very sparse plants initially and the lack of plants in the post sampling may be due to patchiness and not to wind and wave effects.  Crews reported very little floating or uprooted vegetation (submerged or emergent), and most of what was observed was cattail that had been dead prior to the storm.  No blooms or toxins were present during either the July phytoplankton sampling or immediately following Tropical Storm Fay.  A bloom was reported near Port Myacca on 8/29, but a crew sent out Tuesday found no blooms in that area.

 

St. Lucie Estuary

 

During the last week, an average discharge of 1753 cfs occurred at S-80 from C-44.  Average discharge values through S-48 from C-23 and through S-49 from C-24 are unavailable over the past week.  The current weekly average salinities (in bold) at the four monitoring sites in the St. Lucie are given below in parts per thousand (ppt), along with the previous week’s (in parenthesis) and the preferred range (envelope) at the two downstream sensors.  HR1 values are estimated from two days at the beginning of this week.

 

 

Weekly Average Salinity (ppt)

 

Sampling Site

Surface

Bottom

Envelope

Palm City Bridge (S. Fork)

0.17 (1.43)

0.17 (1.44)

 

HR1 (N. Fork)

0.15 (0.92)

0.17(1.20)

 

Roosevelt Bridge

0.20 (1.89)

0.20(1.96)

8.0 – 25.0

A1A Bridge

2.87 (3.82)

9.75 (4.48)

20.0 – 31.0

 

Compared with salinities of the previous week, average salinity in the estuary decreased about 0.8 to 1.8 ppt., except for bottom salinity at A1A Bridge which increased by 5.3 ppt.  All four monitoring stations are reporting salinities below the preferred range.  Salinity conditions in the estuary are considered to be poor based on the salinity preference of the oyster, Crassostrea virginica, and location in the estuary.

 

Caloosahatchee Estuary

 

An average weekly discharge of 10,311 cfs occurred at S-79.  The concentration of chlorides at the Olga Plant was 30 ppm yesterday, up from 22 ppm at the beginning of this reporting period. 

Prior to Tropical Storm Fay, S-78 remained closed with no discharge since June 30th.  S-78 average discharge during the last week was 3993 cfs.  The gates at S-77 have remained closed over the past week.

 

The current weekly average salinities (in bold) at the six monitoring sites in the Caloosahatchee Estuary are given below in parts per thousand (ppt), along with the previous week’s (in parenthesis).

 


 

Weekly Average Salinity (ppt)

Sampling Site

Surface

Bottom

Franklin Locks (S-79)

0.16 (0.16)

0.15 (0.16)

Rt. 31 Bridge

0.16 (0.16)

NR (NR)

I-75 Bridge

0.20 (0.19)

0.18 (0.18)

Ft. Myers Yacht Basin

0.19 (0.28)

0.19 (0.28)

Cape Coral Bridge

0.54 (NR)

1.13 (NR)

Shell Point

7.69 (5.29)

11.45 (7.35)

 

In the estuary, freshwater conditions extend from S-79 downstream to Cape Coral Bridge.  Salinity conditions in the upper estuary east of Ft. Myers are good (30 day average at Ft. Myers = 0.63 ppt).

 

Salinity at Cape Coral Bridge is below the preferred ranges for both oyster, Crassostrea virginica, and seagrass, Halodule wrightii.  Salinity at Shell Point is oscillating with the tide between about 26 ppt to 0 ppt.  Therefore, conditions in the lower estuary between Cape Coral and Shell Point are considered poor.

 

No Karenia brevis, the Florida red tide organism, was detected this week in water samples collected alongshore between Pinellas and Collier counties.

 

Water Conservation Areas

 

Rainfall did not keep up with evapotranspiration everywhere and water depths increased (ft) in some areas and decreased in other, such that:

 

WCA-1:           -  0.06 ft           WCA-3A:         + 0.25 ft

WCA-2A:         + 0.50 ft           WCA-3B:         + 0.07 ft

WCA-2B:         + 0.19 ft           ENP:               -  0.02 ft

 

June through September is usually the time of year when the Greater Everglades (GE) is expected to continuously rise at the rate of some 0.1 to 0.2 feet per week.  However, with the arrival of Tropical Storm Fay it is no longer necessary or appropriate to track this re-hydration rate.  The GE has now reached a state where most of the sentinel gages are at least 2 feet deep and large areas of the GE are currently over 2.5 feet.  This 2.5 foot depth is a generalized threshold for tree island inundation where continuous inundation of more than 120 days is a potential health hazard for islands.  Thus, Inundation Days are now being tracked and some areas of WCA-3A are now 35 days above the tree island threshold.

 

WCA-1 has dropped below the regulation schedule.  All the other WCA stages are above regulation, especially WCA-2A, which has been above regulation since Oct. 1, 2007 (i.e., the last 11 months). It is not possible to restore drowned tree islands in WCA-2A under this hydrologic regime.

 

Everglades National Park

 

For the most part, stages in Everglades National Park (ENP) increased.  Water levels rose over two feet in Shark River Slough (station P33) and nearly 1.5 feet at the Taylor Slough Bridge last week, while water level was unchanged in the ENP panhandle.

Salinity declined slightly across Florida Bay.  In the eastern bay, salinity held steady in the upper 30s at Duck Key but declined slightly to under 31 psu at the Little Madeira Bay mouth platform.

Creek salinity continued to decline last week, although there was a marked pattern of flashy reversals likely due to the prevailing southerly outflow winds from Hurricane Gustav.  Trout Creek. salinity decreased into the middle-upper teens during the week but briefly spiked to over 25 psu on Sunday, 8/31 before dropping back into the middle-upper teens by Monday morning (9/1).  Taylor River pond salinity decreased steadily to under 15 psu throughout the week (NOTE: this is still high, as average concentrations here are in the single digits by August).  The Taylor River (TR) 30 day moving average salinity (used for tracking the Florida Bay MFL criterion) decreased relative to last week’s reading (32.6 psu, 8/24) to 28.6 psu as of 8/31.  Terrapin Bay held steady in the upper 20s throughout the week.  The central Bay platform at Whipray Basin saw salinity holding steady in the low 40s throughout the week.  Salinity held at seasonal concentrations in the upstream reaches of Shark River Slough, measuring below 1 psu at the Tarpon Bay platform.

 

Water Supply

 

Water levels remained largely unchanged across most of the District.  After enjoying a substantial rise (increase) as a result of Tropical Storm Fay two weeks ago.  Water levels in the upper and lower Kissimmee Basin are now above their average conditions for their respective periods of record, although water levels in the lower Kissimmee Basin recorded the most substantial increases during the past week.  Water levels in the Lower West Coast are mostly above their historical averages and are now above levels that were recorded in 2006.  Water levels in the Lower East Coast are now substantially above their historical averages.  Water levels in the Upper East Coast are now significantly above their historic averages and close to their highest recorded values.  Surface and groundwater levels in Water Conservation Areas 1, 2 and 3 are now slightly above their historic averages this week.

 

Eight out of the eleven water supply risk indicator parameters are now in the “low” risk category, including the CPC Precipitation Outlook, Palmer Index for Tributary Conditions, the Lake Okeechobee Seasonal and Multi-seasonal Net Inflow Forecast, and Water Conservation Areas 1, 2A and 3A.  The projected Lake Okeechobee Stage is now in the “low” risk category.

 

Eight out of the eleven water supply risk indicator parameters are now in the “low” risk category, including the CPC Precipitation Outlook, Palmer Index for Tributary Conditions, the Lake Okeechobee Seasonal and Multi-seasonal Net Inflow Forecast, and Water Conservation Areas 1, 2A and 3A.  The projected Lake Okeechobee Stage is now in the “low” risk category.

 

Three out the eleven water supply risk indicators are now in the “medium” risk category, including LEC Service Areas 1, 2 and 3.

 

LORS2008 (Lake Okeechobee Regulation Schedule)

 

Stages in Lake Okeechobee have risen to within one foot of the intermediate band, which calls for discharges of up to 4000 cfs at S-77 and up to 1800 cfs at S-80.  The United States Army Corps of Engineers (USACE) indicated that the current volumes and anticipated duration of local runoff would be factored in to their discharge decision.

 

 

 

 

 

CC:      George Horne