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:            August 26, 2008

 

SUBJECT:     Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

No Lake Okeechobee regulatory releases to the south or estuaries are recommended.

 

Background

 

Showers and storms focused interior south on Tuesday, interior west Wednesday and west on Thursday.  Steering flow remains from the south this morning.  This is not a dry direction.  Look for seabreeze enhanced showers/storms to focus over interior areas south and around Lake Okeechobee this afternoon.  High pressure over the Bahamas should build a little more westward on Wednesday, so storms should focus interior southwest and west tomorrow afternoon.  Activity should then decrease and focus west Thursday and south on 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 7.46 inches of rainfall, bringing this month’s total rainfall to 9.46 inches (177% of normal).  The Lower Basin received 9.04 inches to bring this month’s total to an astounding 11.48 inches (239% of normal).

 

Water levels in all of the upper basin lakes are above their regulation schedules except for Lake Gentry.  Releases are being made from Lake Hart (500 cfs), East Lake Tohopekaliga (709 cfs), Lake Tohopekaliga (2,044 cfs), The Alligator Chain (319 cfs) and Lake Gentry (319 cfs).

 

According to the Florida Fish and Wildlife Cooperative Research Unit at The University of Florida, all known snail kite nesting in the Kissimmee Basin has ended.  This includes young birds being fed near nesting sites.

 

Due to the heavy rainfall associated with Tropical Storm Fay, discharge from Lake Kissimmee has been increased to approximately 7,000 cfs. Discharge at S65C is 11,000 cfs.

 

Water depths on the floodplain within the restoration project currently range from 2.5 – 6.8 feet.  The floodplain in the restored reach is completely inundated at this time.

 

From 08/19/08 to 08/26/08 dissolved oxygen (DO) concentrations in the Kissimmee River ranged from 4.8 mg/L to 0.36 mg/L and averaged 1.7 mg/L.  The highest DO readings occurred during and shortly after Tropical Storm Fay’s passage over the Kissimmee Basin.  The increase in DO concentration is likely due to re-aeration from heavy rainfall and high winds.  As flows through the restoration project increased over the past week, DO concentrations in the river channel decreased steadily and are currently below the 2 mg/L level of concern for fish.  However, the floodplain in the restoration area is completely inundated and there are likely areas on the floodplain with higher DO concentrations where fish can take refuge.  A similar phenomenon was observed during and after hurricanes Frances and Jeanne in 2004.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 13.63’ NGVD, which is 2.29’ higher than a week ago, 2.95’ higher than a month ago, and 4.10’ higher than it was a year ago.  The current stage is 0.62’ below the historical average for this date, and 0.49’ above the simulated historical average for the current regulation schedule (LORS2008).  Total reported inflows are 28105 cfs, with major contributions from the Kissimmee River (14398 cfs), S84 (3524 cfs), S71 (3373 cfs), S72 (1474 cfs), S191 (2453 cfs), and the L8 at canal point (997 cfs).  Back pumping from the Everglades Agriculture Area (EAA )is occurring through S4 at 821 cfs.  No outflows are reported and no flow data are available for the S77 or S308.  Total reported flows also do not include an estimated 4000 cfs entering the lake from Fisheating Creek as reported by USGS.

 

Field crews began conducting post-Fay assessments of water-quality, phytoplankton, and submerged aquatic vegetation (SAV) last Friday (8/22/08).  Initial reports show increased turbidity across most of the nearshore zone and an absence of algal blooms.  Underwater light conditions for SAV growth ranged from poor (secchi depth:total depth ratio of 0.1) to marginal (sd:td of 0.3-0.4), with the southern shoreline having the least turbidity and the northern shoreline having the greatest.  High flows in Fisheating Creek appear to be maintaining low turbidity across Fisheating Bay.  By contrast, high flows from the Kissimmee are contributing to the re-suspension of mud sediments deposited in that part of the lake in recent years.

 

Post-storm sampling at SAV sites surveyed just 2-3 weeks ago indicates that the SAV community remains largely intact despite maximum sustained winds near 60 mph along the western shoreline during the storm.  However, continued development of existing SAV beds will be slowed if deep, turbid water conditions persist.  Due to the rapid increase in water levels, many of these beds are now at water depths of 1.0-1.5 m or greater.  However, increased lake stage has also resulted in the re-hydration of shoreline areas that historically have contained extensive SAV beds.  An aerial survey conducted on Monday indicated that water clarity in these newly flooded areas is suitable for SAV germination and growth.

 

Emergent wetland vegetation along the shoreline also remains intact.  Water depths have increased to > 1 m along the outer wall of cattail and spikerush that developed during the drought.  Both of these species are tolerant of deep-water conditions in wetlands such as the Everglades but may not persist at these water depths in the high-energy wave environment of the lake shoreline.  Bulrush stands that form an outer wall along the western shoreline under normal lake stages have re-flooded.  Extensive areas of terrestrial herbaceous vegetation that established across the littoral zone during the drought have also flooded.  Transient water-quality problems including high nutrient levels, algal blooms, and low nighttime dissolved oxygen may occur in these areas as this upland vegetation dies and begins to decompose.

 

St. Lucie Estuary

 

During the last week, an average discharge of 915 cfs occurred at S-80 from C-44.  Monday’s discharge was 1,451 cfs.  An average discharge of about 3,000 cfs occurred last week through S-49 from C-24.  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.


 

 

Weekly Average Salinity (ppt)

 

Sampling Site

Surface

Bottom

Envelope

Palm City Bridge (S. Fork)

1.43 (8.07)

1.44 (9.56)

 

HR1 (N. Fork)

0.92 (7.71)

1.20 (12.81)

 

Roosevelt Bridge

1.89 (11.13)

1.96 (13.80)

8.0 – 25.0

A1A Bridge

3.82 (19.69)

4.48 (24.63)

20.0 – 31.0

 

Compared with salinities of the previous week, average salinity in the estuary decreased about 8.12 to 20.15 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 14,457 cfs occurred at S-79.  Yesterday’s discharge was 13,556 cfs.  The concentration of chlorides at the Olga Plant was 22 ppm yesterday, down from 50 ppm at the beginning of this reporting period.

 

Based on the USGS flow meter located just below S-77 there was an average weekly discharge of 433 cfs.  Prior to Tropical Storm Fay, S-78 remained closed with no discharge since June 30th.  S-78 opened on Aug. 18th with an average discharge during the last week of about 5,920 cfs.  Monday’s discharge was 4,987 cfs.

 

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 (0.25)

0.15 (0.25)

Rt. 31 Bridge

0.16 (0.26)

NR (NR)

I-75 Bridge

0.19 (0.33)

0.18 (0.30)

Ft. Myers Yacht Basin

0.28 (0.87)

0.28 (1.08)

Cape Coral Bridge

NR (NR)

NR (NR)

Shell Point

5.29 (22.17)

7.35 (23.57)

 

In the estuary, freshwater conditions extend from S-79 downstream to Shell Point.  Salinity conditions in the upper estuary east of Ft. Myers are good (30 day average at Ft. Myers = 0.84 ppt).  However, this morning’s reading from the Sanibel Captiva Conservation Foundation’s (SCCF) dissolved oxygen sensor was < 3 mg/l near Ft. Myers.

 

Salinity at Cape Coral Bridge (based on other recorders) 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 20 ppt to 0 ppt and Tuesday morning’s reading for D.O. was < 4 mg/l (SCCF sensor).  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 or in offshore samples collected west of Sanibel Island (Lee County).


Water Conservation Areas

 

June through September is usually the time of year when the Greater Everglades (GE) is expected to continuously rise at the rate of approximately 0.1 to 0.2 foot 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 deep.  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.

 

All the WCA stages are above regulation.  WCA-2A has been above regulation since October 1, 2007 (i.e., the last 11 months).

 

Everglades National Park

 

Tropical Storm Fay delivered some significant rainfall to the southern Everglades and Florida Bay last week.  However, there was a large amount of spatial variability (rain at the marine and wetland platforms ranged from 1.7” to 6.9”).  Water levels were up by approximately 5” last week in Shark River Slough (station P33) and by just over 3” in the Everglades National Park (ENP) panhandle (station EVER6).  In Taylor Slough, a part of the system where water levels had been below average so far this wet season, water level increased by 11.6” at Taylor Slough Bridge and by 10.3” downstream at Craighead Pond in just one week, allowing both areas to actually surpass their respective seasonal averages.

 

Salinity trends across Florida Bay remained mixed last week, with concentrations holding above average in many areas, but with some sign of declining salinity.  In the eastern Bay (Duck Key, L. Madeira Bay mouth) salinity held in the mid-upper 30s for much of the week.  Taylor River pond salinity dropped into the mid-20s by the end of the weekend.  The Taylor River (TR) 30 day moving average salinity (FL Bay MFL criterion = 30 psu) decreased slightly from last week’s reading (33.9 psu), down to 32.6 psu as of Sunday, 8/24.  Salinity also dropped to just below 30 psu in McCormick Creek.  The central Bay platform at Whipray Basin also posted declining salinity for the week, falling to the lower 40s by Sunday, 8/24.  Salinity held near seasonal concentrations in upstream reaches of Shark River, where salinity is nearly fresh (close to 1 psu).

 

Water Supply

 

Water levels across the District generally benefited as a result of Tropical Storm Fay.  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 at or above their historical averages.  Water levels in the Lower East Coast are now substantially above their historical averages and approaching their highest.  Water levels in the Upper East Coast are now significantly above their historic averages.  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.

 

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)

 

Rainfall from Tropical Storm Fay significantly increased Lake Okeechobee inflows during the past week.  The Lake Okeechobee stage increased by a record 2.3 feet during the past week.  Stages in Lake Okeechobee  have risen above the water shortage line and base flow discharges are now allowed.  However, given the volume of water still being discharged due to local runoff, no releases are recommended at this time.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CC:      George Horne