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 23, 2008

 

SUBJECT:     Weekly Environmental Conditions for Systems Operations

 

Summary

 

Inflows from the tributary basins have continued to taper off and are now in the wet tributary hydrologic conditions.   Stages in Lake Okeechobee (Lake) are within one foot of the intermediate band.  The LORSS recommended discharges are up to 3000 cfs at S-79 and up to 1170 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, with some areas of algal bloom formation on the Lake, and conditions in the estuaries are poor.

 

Background

 

Rains Tuesday, then significantly drier tomorrow into the weekend.  A developing trough over the southeast United States will focus widespread showers, and storms east through south of Lake Okeechobee Tuesday.  As the trough moves eastward and a “cut-off” low forms, drier air will be forced down the peninsula tonight through Thursday.  Some showers will linger near the coast Wednesday dry conditions overwhelm the entire District on Thursday and Friday.  Rains will begin to sneak back into south Florida Saturday with some potential for significant rains south and east Sunday or Monday.  The next ten days precipitation outlook is below average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received approximately 0.41 inches of rainfall to bring the 30 day total to 3.92 inches (61% of average).  The lower basin received approximately 0.5 inches to bring the 30 day total to 4.09 inches (67% of average).  Water levels in all of the upper basin lakes continue to closely follow their regulation schedules.

 

Releases are being made from Lake Myrtle (70 cfs), East Lake Tohopekaliga (92 cfs), Lake Tohopekaliga (71 cfs), and The Alligator Chain (43 cfs).

 

Discharge from Lake Kissimmee decreased from 1,800 > cfs to approximately 800 cfs and discharge at S65C is down from over 3,000 cfs to 1,700 cfs.

 

Water depths on the floodplain within the restoration project have decreased by about 1.0 foot over the last week.  In general, floodplain depths in the restored area range from 0.5 feet to 3.0 feet.

 

From 9/16/08 to 9/23/08 dissolved oxygen (DO) concentrations in the Kissimmee River ranged from 0.3 mg/L to 2.8 mg/L and averaged 1.4 mg/L, a slight increase from last week.  DO concentrations are still below levels of concern at certain times but are showing signs of improvement.


Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 15.06’ NGVD, which is 0.10’ lower than a week ago, 1.95’ higher than a month ago, and 5.38’ higher than it was a year ago.  The current stage is 0.36’ above the historical average for this date, and 1.42’ above the simulated historical average for the current regulation schedule (LORS2008).  Total reported inflows are 2261 cfs, with the greatest contributions from the Kissimmee River (1735 cfs), S71 (157 cfs), and Fisheating Creek (151 cfs).  Pulse releases to the estuaries continue at 3304 cfs through the S308 and approximately 4000 cfs through the S77.  Other outflows include 201 cfs to the L8 at Canal Point.

 

The annual mapping of the entire submerged aquatic vegetation (SAV) community was completed in early August (prior to Tropical Storm Fay).  The abundance of SAV at approximately 377 shoreline sites has been documented and preliminary results indicate that SAV covers a total of 35,834 acres.  This is an increase of 7654 acres of SAV coverage from last year’s annual mapping (28,180 total acres).  Chara remains the dominant plant species, covering 28,268 acres along the southern and western shorelines.  Vallisneria increased in areal coverage from 494 acres last year to 9405 acres this year and is most abundant in Fisheating Bay.  Hydrilla, Najas, and Potamogeton were not found last year but this year covered 1150, 1208, and 247 acres, respectively.

 

A bloom of cyanobacteria, tentatively identified as the toxin-producing Microcystis, spread rapidly across the northern part of the lake last week, and bloom conditions also were observed near Pahokee on Thursday.  Yesterday, field crews reported a moderate bloom in Fisheating Bay but no evidence of bloom activity at the south end of the lake.

 

Periodic sightings of the non-native Purple Swamphen have occurred on the lake this year.  Approximately one dozen birds were spotted yesterday in Bay Bottom at the south end of the lake.  Florida Fish and Wildlife Conservation Commission (FFWCC) is the lead agency responsible for their eradication.

 

St. Lucie Estuary

 

During the last week, an average discharge of 1653 cfs occurred at S-80 from C-44 and 2195 cfs at S308.  Flow data of C-23 and C-24 were currently inaccessible due to technical issues, but the discharge should be insignificant considering that very limited rainfall occurred 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).

 

 

Weekly Average Salinity (ppt)

 

Sampling Site

Surface

Bottom

Envelope

Palm City Bridge (S. Fork)

0.33 (0.26)

0.38 (0.26)

 

HR1 (N. Fork)

2.23 (0.36)

5.45 (0.49)

 

Roosevelt Bridge

4.32 (0.93)

6.36 (1.21)

8.0 – 25.0

A1A Bridge

14.77 (6.55)

23.42 (18.29)

20.0 – 31.0

 

Average salinity increased about 0.1 ppt in the South Fork to about 8.2 ppt at the A1A Bridge compared with that of the previous week.  All four monitoring stations are reporting salinities below the preferred range, except for the bottom salinity at A1A Bridge.  Salinity conditions in the estuary are still 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 3745 cfs occurred at S-79, 2328 cfs at S-78, and 2634 cfs at S-77.  The concentration of chlorides at the Olga Plant was 43 ppm yesterday, down from 45 ppm at the beginning of this reporting period.  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)

0.24 (0.22)

0.24 (0.22)

Rt. 31 Bridge

0.24 (0.22)

0.24 (NR)

I-75 Bridge

0.26 (0.25)

0.27 (0.23)

Ft. Myers Yacht Basin

0.34 (0.41)

0.36 (0.43)

Cape Coral Bridge

3.45 (2.63)

5.17 (7.00)

Shell Point

16.66 (17.92)

19.42 (22.24)

 

In the estuary, freshwater conditions extend from S-79 to downstream of Ft. Myers.  Salinity conditions in the upper estuary east of Fort Myers are good (30 day average at Fort. Myers equals 0.29 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 29 ppt to 8 ppt.  Therefore, conditions in the lower estuary between Cape Coral and Shell Point are considered poor.

 

Fish and Wildlife Research Institute (FWRI) reports that background concentrations of Karenia brevis, the Florida red tide organism, were detected this week in water samples collected near Cortez (Manatee County) and along the southeastern coast of Sanibel Island (Lee County). All other samples collected between Pinellas and Collier counties did not contain K. brevis.  Monitoring data collected by the River, Estuary and Coastal Observing Network (RECON) of Sanibel-Captiva Conservation Foundation (SCCF) indicated that Chlorophyll concentrations over the last week were about 4.5-5.5 ug/L at Fort Myers and 1.5 to 4 ug/L at Shell Point.  The dissolved oxygen concentration at the two locations ranged from about 4 to 6 mg/L.

 

Water Conservation Areas

 

Water depths in the Greater Everglades (GE) range from a high of 3.99 feet in the southern region of WCA-2B to a low of 1.36 ft in central WCA-1.  The GE has now reached a state where large areas of the GE are currently over 2.5 ft.  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.  The southern region WCA-3A is now 56 days above the tree island threshold, central WCA-2A is now 42 days above this threshold, and the ponded region of WCA-2B is now 70 days above this threshold.

 

WCA-1 stages continue to drop and are below the regulation schedule.  These levels need to stabilize.  WCA-2A stages have dropped precipitously (-0.62 feet), but remains well above regulation, and has been above regulation since October 1, 2007 (i.e., almost 12 months).  WCA-3A stage is unchanged and has been above regulation since mid-July.


Everglades National Park

 

Everglades National Park (ENP) and Florida Bay saw light to moderate rainfall last week, with weekly accumulations ranging between 0.1 – 2.9 inches at marine and wetland platforms.  The basin-wide spatially-averaged weekly RAINDAR totals were 2.4 and 1.2 inches in the ENP and C-111 basins, respectively.  Stages in ENP wetlands increased last week.  Water levels were up by a little over 1 inch last week in Shark River Slough (station P33) and at Taylor Slough Bridge.  To the south, stages increased by approx. 0.5 inches at Craighead Pond, and were nearly unchanged in the panhandle (station EVER6) over the 7 day period.

 

Salinity trends across Florida Bay were mixed.  Salinity remained elevated in parts of the Eastern Bay (Duck Key, mid-upper 30s), but was at seasonable levels in most near shore areas, including L. Madeira Bay mouth (reading in the mid-upper 20s) and the creeks feeding Florida Bay (Trout Creek and Taylor River, concentrations at single digits or teens for much of the week).  Taylor River pond salinity continued to decline last week, allowing the Taylor River platform 30 day moving average salinity to again drop from last week’s reading (17.6 psu), down to 12.1 psu as of Sunday, September 21st.  Salinity was down slightly in the north-central Bay, into the lower-20s at McCormick Creek and into the mid-20s in Terrapin Bay.  The central Bay platform at Whipray Basin saw stable salinity last week, holding in the mid-upper 30s.  Salinity held near seasonal concentrations in upstream reaches of Shark River (Tarpon Bay platform, where salinity is nearly fresh at below 1 psu).

 

Water Supply

 

Water levels declined slightly across most of the District this past week.  Water levels in the upper and lower Kissimmee Basin are now near their average conditions for their respective periods of record.  Water levels in the Lower West Coast are mostly above their historical averages although a few wells declined slightly.  Water levels in the Lower East Coast are now near or slightly below their historical averages.  Water levels in the Upper East Coast remain above their historic averages.  Surface and groundwater levels in Water Conservation Areas 1, 2 and 3 continue to remain 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 are within one foot of the intermediate band, and tributary conditions are wet, which calls for discharges of up to 3000 cfs at S-79 and up to 1170 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