MEMORANDUM

 

 

TO:            Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:      SFWMD Staff Environmental Advisory Team

 

DATE:       April 15, 2008

 

SUBJECT: Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

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

 

Background

 

Limited light shower activity.  A low pressure system currently located about 500 miles east of Melbourne is expected to exit to the northeast by Thursday.  Some moisture and clouds are wrapping around the back side of this low and are generating scattered showers near the east coast of Florida.  Expect breezy conditions with some of these showers affecting northeastern portions of the District today.  High pressure will then build in behind this low bringing dry conditions Thursday and Friday.  The next cold front will have limited moisture as it moves into north central Florida Saturday evening resulting in widely scattered light showers Saturday night and Sunday.  The next ten days precipitation outlook is below average with moderate confidence.

 

Kissimmee Watershed

 

The 30 day rainfall total has increased to 4.20 inches (163% of average).  The large rainfall reported last week resulted in stage reversals in several lakes in the upper basin.  The largest reversal was 0.75 ft in Lake Toho, which has the potential to impact on apple snail reproduction and nesting by wading birds and snail kites.  In the upper basin, snail kites continue to nest on East Lake Toho, Lake Toho, and Lake Kissimmee.  A whooping crane continues to nest on Lake Kissimmee.   The discharge from Lake Kissimmee (S-65) continues at approximately 1500 cfs to provide flow to the Kissimmee River and to allow a gradual water level recession on the floodplain.  No other releases are being made in the upper basin.  Flow has been reestablished to the Kissimmee River for 265 days (S-65 re-opened on 07/18/07).   The inflow from the upper basin continues to inundate a portion of the floodplain in the Phase I area of the Kissimmee River Restoration Project.

 

Dissolved oxygen concentrations in the river channel of the Kissimmee River ranged from 1.8 mg/L to 4.7 mg/L with an average of 3 mg/L.  Hydrilla treatment began in Lake Cypress last week and continues this week.  It is anticipated that releases from Lake Toho will resume on Thursday (April 17).

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 10.48’ NGVD, which is the same as a week ago and 0.30’ higher than a month ago.  The current stage is 0.41’ higher than it was a year ago and 3.61’ below its historical average for this time of year.  Total reported inflows exceed 4800 cfs and include the Kissimmee River (~1900 cfs), S71 and S72 (~130 cfs), S84 (~40 cfs), S91 (~2160 cfs), and the L8 at Canal Point (~640 cfs).  Although not reported, additional inflows likely continue through the S77 as well.  No outflows are reported.

March water-quality monitoring results are now available.  Fifteen of the 25 monitoring stations had sufficient water for sampling.  Total P averaged 141 ppb lake wide (compared to 152 ppb in February) and 81 ppb at near shore stations (compared to 77 ppb in February).  Total suspended solids (TSS) averaged 33 ppm lake wide (compared to 54 ppm in February) and 25 ppm at near shore stations (compared to 26 ppm in February).

 

The monthly submerged-aquatic-vegetation (SAV) survey was completed last week.  Water clarity was generally conducive to plant growth with secchi depths greater than 50% of total depths at 26 of the 30 sites sampled.  The macroalga Chara remains the dominant SAV species and was found at 12 of the 30 sites.  One species of vascular SAV, Vallisneria americana, continues to be present in very low density at a few sites around King’s Bar on the northern shoreline and a few sites along the western shoreline. Potamogeton illinoensis (pondweed) was observed in very low density along the western shoreline near Observation Island.

 

St. Lucie Estuary

 

There were no releases through S-80 over the past week.  Discharge of 103 cfs occurred at S-97 on the C-23 canal and discharge at S-49 on the C-24 canal was unavailable this week.  The current weekly average salinities at the four monitoring sites in the St. Lucie are given below in parts per thousand (ppt).  Current weekly averages (in bold) may be compared to last week’s data (in parenthesis).

 

 

Weekly Average Salinity (ppt)

 

Sampling Site

Surface

Bottom

Envelope

Palm City Bridge (S. Fork)

10.13 ( 11.55)

10.41 (12.64)

 

HR1 (N. Fork)

9.19 (12.09)

13.40(13.45)

 

Roosevelt Bridge

13.08 (16.22)

15.03 (16.98)

8.0 – 25.0

A1A Bridge

23.60 (25.35)

27.52 (27.56)

20.0 – 31.0

 

During the past week, average salinity decreased about 1-2 ppt throughout the estuary.  Both the surface and bottom salinity are in the preferred range at the Roosevelt Bridge, and at the A1A Bridge.  Based on the salinity tolerances of the oyster, Crassostrea virginica, salinity conditions in the estuary are good.  The current surface salinity of 13 ppt at the Roosevelt Bridge is 15 ppt below the maximum weekly average of 28 ppt achieved in May 2001 during the 2000 – 2001 drought.

 

Caloosahatchee Estuary

 

Discharge of 364 cfs occurred at S-79 last week.  Discharge from S-77 into Lake Okeechobee averaged 393 cfs last week.  The concentration of chlorides at the Olga Plant is 155 mg/l.  Weekly average salinities for specific sites are given below in parts per thousand (ppt).  Current weekly averages (in bold) may be compared to last week’s data (in parenthesis).

 

 

Weekly Average Salinity (ppt)

Sampling Site

Surface

Bottom

Franklin Locks (S-79)

9.03 (14.45)

9.60 (14.50)

Rt. 31 Bridge

9.39 (15.06)

9.58(16.15)

I-75 Bridge

NA (NA)

16.04 (20.17)

Ft. Myers Yacht Basin

19.95 (23.19)

21.16 (23.32)

Cape Coral Bridge

26.87 (28.06)

27.74 (28.77)

Shell Point

33.44 (34.33)

34.25 (35.22)

 

Average salinities decreased ~ 5 ppt in the upper estuary and 1 to 2 ppt in the lower estuary.  Salinity at the Ft. Myers surface sensor fell just below the 1-day MFL criterion of 20 ppt.  The current surface salinity of 9 ppt at S-79 is 11 ppt below the maximum weekly average of 20 ppt achieved in May 2001 during the 2000 – 2001 drought.  Salinity at the Cape Coral Bridge is near the upper limit of the optimal range for the oyster, Crassostrea virginica.  Conditions in the upper estuary east of Ft. Myers are poor due to high salinity.  Conditions downstream of Cape Coral are fair considering the salinity tolerances of oysters.

 

FWRI reports that a bloom of the marine cyanobacteria Trichodsmium was reported in the Pine Island Sound area of Lee County, however no impacts have been reported.  Very low concentrations of Karenia brevis, the Florida red tide organism, were detected this week alongshore of Sarasota County and southern Collier County.

 

Water Conservation Areas

 

Recession rates were high in WCA-1 due to the movement of water north to Lake Okeechobee, the water deficit, and the movement of water south through the S-10’s.  Continued recessions may bring the water levels in WCA-1 below the one foot mark in time for Ibis to attempt a late season nesting.  For the rest of the system water levels continue to stay level or actually increase.  This environment does not concentrate fish into shallow sloughs, as prey for wading birds.  Depths continue to be too high in the WCA’s for wading bird foraging.  Stages in WCA-1 first increased and are now declining, and approaching the Regulation Schedule, WCA-2A marsh remains well above regulation, and WCA-3A stages are slightly above the zone E1 of the regulation schedule, for protection of the Cape Sable Seaside Sparrow.

 

Everglades National Park

 

Everglades National Park (ENP) wetland water levels showed mixed trends last week, but were generally higher as a result of rainfall some 10 days ago.  Water level climbed by nearly 1foot at Taylor Slough Bridge.  The southern part of Taylor Slough (at Craighead Pond) also posted a weekly water level increase of 2.4”.  To the north, in the Shark River Slough. system, water level was up by 1.8” at station P33 over the week.  Water level in the panhandle (station EVER6) responding differently to the rainfall, showing only a short increase before dropping back by the week’s end to where it measured last Sunday (4/6, at 0.2’ below ground surface).  This may be a result of the station’s proximity to the C-111 canal (acting to drain nearby wetlands in which stage was higher than that in the canal just after the rain event).

 

Salinity in Florida Bay declined in response to rain events from over a week ago.  In the Taylor ponds, salinity fell to below 20 psu at both Pond 5 (USGS station) and Argyle Hendry (ENP station TR).  Salinity also dropped a bit in the north-central Bay areas of McCormick Creek and Terrapin Bay, where concentrations fell towards or just below 30 psu.  Local rainfall helped salinity drop into the lower-30s last week at the central Bay station in Whipray Basin, though it increased slightly to 35 psu by the weekend.  These salinity concentrations across Florida Bay are near seasonal norms.  The most notable change in salinity occurred in the upstream reaches of Shark River (Tarpon Bay platform), an area where salinity has remained very high for much of the dry season: the daily mean measurement here dropped to 10.7 psu as of Sunday, 4/13.  While this is still slightly above this area’s seasonal average, it marks a substantial decline (last week concentrations were approaching 20 psu).

 

Water Supply

 

Water levels in the upper and lower Kissimmee Basin are now near their historical average conditions for this time of year.  Water levels in the Lower West Coast are a “mixed bag” of slightly higher and lower than historical averages, depending on the degree of confinement of the aquifers.  Water levels in the Lower East Coast are near or slightly above their historical averages and wells recorded modest increases or decreases, depending on proximity to well-fields.  Water levels in the Upper East Coast remain well above their historic averages.  Surface and groundwater levels in Water Conservation Areas 1 and 2 are now above their historic averages as a result of local rainfall.  Water levels in WCA 3A have rebounded to near their historic averages this week.  Water levels in the southernmost portion of Miami-Dade County are now near their average historic conditions.

 

There was a modest improvement in the Water Supply Risk Indicators for this week, with the Palmer Index for Lake Okeechobee tributary conditions improving from medium to low risk.  Four out of eleven risk measures are in the “high” risk category including the projected Lake Okeechobee Stage (SSM), and Lower East Coast service areas 1, 2 and 3.  The Climate Prediction Center Precipitation Outlook remains in the “medium” risk category.

 

The Lake Okeechobee Seasonal and Multi-seasonal Net Inflow Forecast, and Water Conservation Areas 1, 2A and 3A continue to be in the “low” risk category

 

WSE (Lake Okeechobee Regulation Schedule)

 

The current Lake Okeechobee stage remains in the Water Shortage Management zone and is unlikely to move back into Zone E in the next several months during the persistent La Niña climactic conditions.

 

 

 

 

 

 

 

 

 

 

 

 

CC:   George Horne