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 4, 2007

 

 

SUBJECT:         Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

No regulatory releases to the south or estuaries are recommended.

 

Background

 

Well below average rains likely across the Kissimmee Valley this week.  Look for low pressure a few hundred miles east of Jacksonville to focus showers/storms southeast today, then south tomorrow and Thursday.  This same low will drive drier air across central Florida to limit rainfall there.  Forecast skill becomes low by the end of the week, but more below average rainfall seems the most probable scenario.  The next ten days precipitation outlook is Below Average with Moderate confidence.

 

Kissimmee Watershed

 

The upper Kissimmee Basin received 0.74 inches of rainfall over the last 7 days to bring the 30-day total to 2.99 inches (43% of average) and the lower basin received 1.90 inches to bring the 30-day total to 3.62 inches (58% of average) (Daily Rainfall Report for 09/04/07).

 

Stages in most of the upper basin lakes have been stable over the last seven days.  The stage in Lake Toho has increased slightly in part because of increased inflow from Shingle Creek.

 

Snail kites continue to nest on Lake Tohopekaliga.

 

Flow has been reestablished to the Kissimmee River for 48 days (S-65 re-opened on 07/18/07).  Discharge at S-65 continues at approximately 500 cfs.

 

For the last week, the concentration of dissolved oxygen in the river channel has remained above thresholds of concern with mean daily values above 6 mg/L for the previous week.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 9.55’ NGVD today, which is 0.02’ lower that it was a week ago and 0.10’ higher than it was a month ago.  The current stage is approximately 4’ below its historical average for this time of year.  Surface inflows are 1392 cfs compared with only 530 cfs last week.  These values do not include gravity inflows through the S77 (164 cfs) and S308 (not reported) structures.  No surface outflows are reported.

 

During August, 21 of the 27 water quality sampling sites had sufficient water for sampling.  TSS values averaged 8 mg/L and TP values averaged 85 ppb.  In April, the last time the same 21 sites were sampled, mean TSS was 60 mg/L and mean TP was 175 ppb.  No nearshore bloom formation was observed during a helicopter flight on August 29 that covered most of the lake shoreline.  Data from the August bloom buster survey are not yet available.

In the littoral zone, spikerush (Eleocharis) is germinating in scattered clumps along the west wall.  About 50-100 acres of this species have become established in < 1’ of very clear water.  This species provides habitat for fish and wildlife.  Approximately 10,000 acres of torpedograss have been treated this summer.  No regrowth was reported at six sites that were treated this year and at two sites that were treated in 2006.  Dominant vegetation at these sites included beakrush (Rhyncospora) and sedges.  One site treated in 2005 had <25% control and contained abundant torpedograss.  Two other sites had >95% control and were dominated by desirable wetland species including buttonbush (Cephalanthus), maidencane (Panicum), arrowhead (Sagittaria) and water lily (Nymphaea) as well as some upland weeds.

 

St. Lucie Estuary

 

No releases occurred at S-80 over the past week.  Weekly average salinities at the four monitoring sites in the St. Lucie are given below in parts per thousand (ppt).

 

 

Weekly Average Salinity (ppt)

 

Sampling Site

Surface

Bottom

Envelope

Palm City Bridge (S. Fork)

5.2

5.9

 

HR1 (N. Fork)

7.8

11.4

 

Roosevelt Bridge

11.8

12.3

8.0 – 25.0

A1A Bridge

19.5

26.0

20.0 – 31.0

 

Average weekly salinity in the estuary increased slightly since the last report.  Local freshwater inflow continues to maintain surface salinity at both the Roosevelt Bridge and A1A Bridge within or near the preferred ranges.  Therefore, salinity conditions in the estuary are good.

 

Seagrasses near the St. Lucie Inlet were monitored on August 23.  At site 2, north of the inlet, Syringodium shoot counts and canopy heights were similar to those observed last month.  Many areas of the site are now densely covered by Halophila johnsonii and/or Halodule wrightii.  Bottom salinity was 28 ppt and visibility was fair to good (Secchi 0.8 m).

 

At Site 3, south of the inlet. seagrass conditions were similar to those observed last month:  A dense, healthy fringe of Halodule wrightii is present along the shoreline. Halophila johnsonii and to a lesser extent Halophila decipiens and Halodule wrightii are present in small patches within the former Syringodium bed.   Halodule wrightii and Halophila johnsonii are present along the offshore shoal.  The Syringodium bed at this site was buried during the 2004 hurricanes and has not recovered.  However, several small patches of Syringodium are currently present at the site.

 

Caloosahatchee Estuary

 

During the past week, discharge at S-79 averaged 266 cfs for the week.  Chloride concentration at the Olga Plant is presently 73 mg/l.  Average salinity at the monitoring sites in the upper Caloosahatchee Estuary decreased over the past week.  Data for specific sites are given below in parts per thousand (ppt).

 

 

Weekly Average Salinity (ppt)

Sampling Site

Surface

Bottom

Franklin Locks (S-79)

6.9

7.0

Rt. 31 Bridge

NA

8.4

I-75 Bridge

7.1

10.6

Ft. Myers Yacht Basin

11.7 *

NA

Cape Coral Bridge

19.3

* based on three-day average.

 
19.6

Shell Point

30.5

32.3

While the weekly average salinity at Ft. Myers remains above 10 ppt.  The daily average salinity fell below 10 ppt on Sept 3, 2007 for the first time since Oct. 30, 2006.  In the lower estuary and San Carlos Bay salinity condition are good.

 

FWRI reports that 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

 

The EPA gauges indicated stable water stages in WCA-1 and NE Shark River Slough, rising water levels in WCA-2B, and falling water levels in WCA-2A, 3A and 3B.  At this time of year, falling stages in the Everglades equate to “Poor” hydrologic conditions.  If depths continue to drop below 1 ft during the 2007 wet season, then there will be extended dry conditions in the Spring of 2008 which will prevent wading birds from feeding and may cause significant peat fires to erupt.  Like last week, stages in WCA-1 are below regulation but still in Zone A2, stages in WCA-2 are at regulation, and stages in WCA-3 are below regulation.

 

Everglades National Park

 

Water levels decreased for another week at all Everglades National Park (ENP) platforms.  Depths at the Taylor Slough Bridge (TSB) water level plunged by 5.6”, another week of > 5” weekly recession.  As a result, the TSB stage is 1.5 ft lower than it was this time last year, and 2.5 ft lower than it was this time two years ago.  In the panhandle region (EVER 6), water level was down by just over 2.25”.  Stage at Craighead Pond (CP) & to the north in Shark River Sl. (P33) dropped by 1.2” & 1.4” over the 7 day period, respectively.  These recession rates are unusual for this time of the year when water levels are typically still increasing.

 

One would think that salinity in the mangrove transition zone would rise with falling stage.  However, local rainfall and possibly a long lag time between affects of stage change on salinity, has prevented salinity from increasing last week.  The platform at the mouth of Little Madeira Bay saw salinity holding just below 20 psu for another week.  Salinity in the TR ponds remained very low all week (~ 1 psu at Pond 5 & Argyle Hendry).  To the north and west, Tarpon Bay (SRS outlflow) salinity was low, holding near 2 psu for another week.

 

Salinity is holding steady or increasing in the Bay regions of the Park.  Salinity readings in the north-central Bay areas of Terrapin Bay and McCormick Creek increased through much of last week, from the mid-20s towards 30 psu by the weekend (likely, in part, to a mid-week Bay water flow reversal).  In the central Bay, Whipray Basin salinity remained near 40 psu for another week.

 

Water Supply

 

Water levels in the upper and lower Kissimmee Basin and Lower West Coast continue to remain near low levels for their periods of record.  Water levels declined slightly in the coastal areas of the Upper East Coast and Lower East Coast over the past week, but they remain above their historical averages.  Surface and groundwater levels in the Water Conservation Areas are near the historic lowest levels recorded for this time of year also.

 

Six out of eleven water supply risk measures are in the “high” risk category this week including the projected Lake O Stage (SSM), the Palm Index for Tributary Conditions, the LOK Multi-Seasonal Net Inflow Forecast and Lower East Coast Service Areas 1, 2 and 3.

Water Conservation Areas 1, 2A continue to be in the low risk category.  Water Conservation Area 3A changed from “low” to “medium” risk this week.  The CPC Precipitation Outlook remains at “low” risk this week, along with the LOK Seasonal Net Inflow forecast.

 

WSE (Lake Okeechobee Regulation Schedule)

 

The current Lake O stage is at 9.55’ today - remains in the Water Shortage Management zone and is unlikely to move back into Zone E in the next two months.

 

 

CC:   George Horne