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 16, 2008

 

SUBJECT:     Weekly Environmental Conditions for Systems Operations

 

Summary

 

Inflows from the tributary basins have continued 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, and maximum practical discharges to the south if desired or with minimal impact.  The United States Army Corps of Engineers (USACE) initiated a second pulse release on September 16th, with an overall release average of 3000 cfs at S-77 and 1500 cfs at S-80.  Conditions in Lake Okeechobee are fair and conditions in the estuaries are poor.

 

Background

 

Daily scattered shower activity.  An upper level low in the northeastern Gulf of Mexico is forecast to shift eastward the next few days and help bring daily shower coverage back up to more typical levels today through Thursday.  A stalled front boundary in north Florida should also contribute to an increase in daily coverage, particularly Thursday and Friday.  Activity will remain focused over the interior and east today but should then shift to the interior and west Wednesday through Saturday.  The next ten days precipitation outlook is average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received 1.24 inches of rainfall to bring the 30 day total to 10.61 inches (161% of average).  The lower basin received approximately 0.17 inches to bring the 30 day total to 12.04 inches (196% of average).

 

Water levels in all of the upper basin lakes are very close to their regulation schedules.  Releases are being made from Lake Myrtle (70 cfs), East Lake Tohopekaliga (557 cfs), Lake Tohopekaliga (845 cfs), and The Alligator Chain (44 cfs).  All lake releases are lower than last week and releases from Lake Hart and Lake Gentry have ceased.

 

Discharge from Lake Kissimmee decreased from 4,000 > cfs to 1847 cfs and discharge at S65C is down from over 6,000 cfs to 3,320 cfs.

 

Water depths on the floodplain within the restoration project have decreased by about 1.5 feet over the last week.  However, some areas are still as deep as 4.8 feet.

 

From 9/09/08 to 9/16/08 dissolved oxygen concentrations in the Kissimmee River ranged from 0.4 mg/L to 2.1 mg/L and averaged 1.0 mg/L.  Dissolved Oxygen concentrations are still below levels of concern at certain times and have decreased slightly over the past week.


Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 15.16’ NGVD, which is 0.06’ higher than a week ago, 3.91’ higher than a month ago, and 5.55’ higher than it was a year ago.  The current stage is 0.59’ above the historical average for this date, and 1.65’ above the simulated historical average for the current regulation schedule (LORS2008).  Total reported inflows are 4821 cfs, with the greatest contributions from the Kissimmee River (3493 cfs), S71 (439 cfs), and Fisheating Creek (~700 cfs).  Outflows of 130 cfs are reported to the L8 at Canal Point.  Pulse releases to the estuaries are scheduled to resume today.

 

The monthly submerged-aquatic-vegetation (SAV) survey was completed yesterday and 16 of the 32 sites visited had plants.  Last month (pre Tropical Storm Fay) 24 of the 35 sites visited had plants.  Water clarity has decreased with an average secchi depth:total depth ratio of 0.34 compared to 0.96 last month.  The decrease in light conditions along the northwestern shoreline and in Fisheating Bay is a result of tannic conditions while suspended particles are contributing to the lower light levels in the south and west. Water depths at many of the lakeward sites are greater than 2 meters and if these conditions persist it is expected that SAV beds in these area may begin to show signs of stress in the coming months.

 

Monthly phytoplankton monitoring was performed 9/ 15/08.  For the first time in over a year all nine sites had sufficient water for sampling.  Toxin and chlorophyll data are not yet available but minor blooms were observed at most of the northern stations and a more significant bloom was seen in Harney Pond.  An increase in bloom formation may occur as terrestrial vegetation in the newly inundated littoral zone die and release nutrients into the water column.

 

Large areas of spikerush and cattail persist at water depths of 1.6 to 1.7 m along the western shoreline.  The lakeward edge of this vegetation is showing clear signs of stress while plants closer to shore still appear healthy.  Bulrush, an important component of the shoreline vegetation community in the past, is conspicuously absent.

 

St. Lucie Estuary

 

During the last week, an average discharge of 1107 cfs occurred at S-80 from C-44 (including 789 cfs at S308 from the Lake), 170 cfs through S-97 from C-23, and 504 cfs 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).

 

 

Weekly Average Salinity (ppt)

 

Sampling Site

Surface

Bottom

Envelope

Palm City Bridge (S. Fork)

0.26 (0.22)

0.26 (0.22)

 

HR1 (N. Fork)

0.36 (0.29)

0.49 (0.47)

 

Roosevelt Bridge

0.93 (0.92)

1.21 (1.66)

8.0 – 25.0

A1A Bridge

6.55 (6.48)

18.29 (16.66)

20.0 – 31.0

 

Compared with salinities of the previous week, average salinity in the estuary increased only slightly in the estuary (<1 ppt for most locations) except for the bottom salinity at Roosevelt Bridge A1A which decreased by 0.5 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 3016 cfs occurred at S-79 including 1166 cfs at S-77 from the Lake.  The concentration of chlorides at the Olga Plant was 45 ppm yesterday, up from 40 ppm at the beginning of this reporting period.  An average discharge of 1784 cfs occurred at S-78 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)

0.22 (0.21)

0.22 (0.22)

Rt. 31 Bridge

0.22 (0.21)

NR (NR)

I-75 Bridge

0.25 (0.24)

0.23 (0.22)

Ft. Myers Yacht Basin

0.41 (0.23)

0.43 (0.23)

Cape Coral Bridge

2.63 (1.15)

7.00 (1.60)

Shell Point

17.92 (11.16)

22.24 (16.62)

 

In the estuary, freshwater conditions extend from S-79 downstream close to Cape Coral Bridge.  Salinity conditions in the upper estuary east of Ft. Myers are good (30 day average at Ft. Myers equals 0.34 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 33 ppt to 3 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. Additional samples, collected offshore of Sarasota and Lee counties, were also free of any K. brevis.

 

Water Conservation Areas

 

Water depths in the Greater Everglades (GE) range from a high of 4.13 feet in southern region of WCA-2B to a low of 1.43 feet in NE Shark River Slough.  The GE has now reached a state where 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 49 days above the tree island threshold and WCA-2A is now 28 days above this threshold.

 

WCA-1 stages continue to drop and are still below the regulation schedule.  WCA-2A stages are beginning to drop, but remain well above regulation and has been above regulation since Oct. 1, 2007 (i.e., the last 11 months). WCA-3A stage continues to rise and has been above regulation since mid-July.

 

Everglades National Park

 

Last week brought significant rainfall to portions of Everglades National Park (ENP) and Florida Bay due to Hurricane Ike.  However, stages in ENP wetlands showed mixed trends.  Water levels were down by a little over 1” last week in the ENP panhandle (station EVER6), and

by 1.6” for the week at Taylor Slough Bridge.  Stage was nearly unchanged for the week in Shark River Slough. at station P33).  However, in southern Taylor Slough at Craighead Pond, the water level was up by 1.4”.

 

Salinity trends across Florida Bay are finally approaching seasonable values in many areas.  Salinity remained elevated in parts of the Eastern Bay (Duck Key, mid-upper 30s), but fell in most nearshore areas, including L. Madeira Bay mouth (into the mid-20s) and the creeks feeding Florida Bay.  Similarly, Taylor River pond salinity fell into single digits last week.  The Taylor River (TR) 30 day moving average salinity (used for tracking the FL Bay MFL criterion) decreased again from last week’s reading (23.2 psu), down to 17.6 psu as of Sunday, 9/14.  For much of the week salinity held in the mid-upper 20s at McCormick Creek and close to 30 psu in the adjacent northcentral basin of Terrapin Bay.  The central Bay platform at Whipray Basin saw a drop in salinity last week, from the lower-40s early in the week to the mid-upper 30s by the weekend.  Salinity held near seasonal concentrations in upstream reaches of Shark River (Tarpon Bay platform, where salinity is nearly fresh @ below 1 psu.)

 

Water Supply

 

Water levels declined slightly across most of the District after enjoying a substantial rise (increase) as a result of Tropical Storms Fay, Hanna and Hurricane Ike.  Water levels in the upper and lower Kissimmee Basin are now slightly above their average conditions for their respective periods of record.  Water levels in the Lower West Coast are mostly above their historical averages and are now near levels that were recorded in 2006.  Water levels in the Lower East Coast are now near their historical averages – although they have declined over the past week as a result of pre-storm management.  Water levels in the Upper East Coast remain significantly above their historic averages and are 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 – the highest recorded levels were within Water Conservation Area 2.

 

All 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 and LEC Service Areas 1, 2 and 3 (as a result of the removal of water restrictions) are now in the “low” risk category.

 

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, and maximum practical discharges to the south if desired or with minimal impact.  The United States Army Corps of Engineers (USACE) initiated a second pulse release on September 16th, with an overall release average of 3000 cfs at S-77 and 1500 cfs at S-80.

 

 

 

 

 

CC:      George Horne