MEMORANDUM

 

TO:            Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:      SFWMD Staff Environmental Advisory Team

 

DATE:       November 6, 2007

 

SUBJECT: Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

No Lake Okeechobee regulatory releases to the south or estuaries are recommended.  It was recommended that the S-65 flows be reduced from 500 cfs to 250 cfs in order to extend the duration of flow to the Kissimmee River.

 

Background

 

Very little rain the next week or so.  Some limited moisture will begin to move back into eastern and southern areas today ahead of the next cold front.  This moisture should allow an isolated shower or two south later today and tonight.  As the cold front pushes into the area and stalls, scattered showers activity will affect eastern areas Wednesday and Thursday.  A low is then forecast to develop off the coast of the Carolinas which should restore dry conditions over the District.  The next ten days precipitation outlook is below average with moderate confidence.

 

Kissimmee Watershed

Over the last 7 days, the upper Kissimmee Basin received 1.29 inches of rainfall to bring the 30 day total to 2.92 inches (107% of the long-term average) and the lower basin received 0.73 inches to bring the 30 day total to 2.56 inches (99% of the long term average).  Wet season totals were 30.63 inches (100% of average) for the upper basin and 29.32 inches (102% of average) for the lower basin (Daily Rainfall Report 11/1/07).  During the last week, water levels in almost all of the upper basin lakes increased slightly.  Water level in Lake Kissimmee fell approximately 0.2 ft.  The only releases being made in the upper basin are at S-65.

 

Only Lake Tohopekaliga and Lake Gentry had water levels that reached the maximum elevation (high pool) of the regulation schedules by the end of the wet season.

 

Anecdotal observations suggest that native species of submerged aquatic vegetation and apple snails are doing well in Lake Kissimmee, which may be related to the lower water levels.  Flow has been reestablished to the Kissimmee River for 104 days (S-65 re-opened on 07/18/07).  Discharge at S-65 continues at approximately 500 cfs.  In the river channel of the Kissimmee River, mean daily concentrations of dissolved oxygen have been 3 mg/L to 4 mg/L.  It is recommended that the S-65 flows be reduced to 250 cfs in order to extend the duration of flow to the Kissimmee River.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 10.37’ NGVD, which is 0.09’ higher than a week ago and 0.28’ higher than a month ago.  The current stage is 2.29’ lower than it was a year ago and remains almost 5’ below its historical average for this time of year.  Total reported surface inflows are 853 cfs, down from 1249 cfs last week, and include discharges through the S65E (782 cfs) and S191 (71 cfs) structures.  This total does not include gravity flows from WCA1 (approx. 500 cfs) or through the S77 and S308 structures.  No surface outflows are reported.

Recent high winds have increased turbidity in the lake.  Initial results of the November submerged-aquatic-vegetation (SAV) survey indicate that SAV coverage has been maintained at the southern end of the lake despite declining secchi depth readings.  However, continued deterioration in water clarity may reduce SAV cover in the coming weeks.

 

St. Lucie Estuary

 

No releases occurred at S-80 over the past week.  The C-24 canal is discharging about 548 cfs at S-97.  No discharge is occurring at S-49 on the C-23 canal.  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)

1.79

1.84

 

HR1 (N. Fork)

2.12

4.52

 

Roosevelt Bridge

5.63

7.91

8.0 – 25.0

A1A Bridge

15.53

23.84

20.0 – 31.0

 

There was little change in average salinity over the past week.  Only bottom water at the A1A Bridge fell within the preferred salinity range.  Based on the salinity tolerances of the oyster, Crassostrea virginica, salinity conditions in the estuary are poor to fair.

 

Caloosahatchee Estuary

 

Discharge at S-79 averaged 24 cfs over the past week.  The concentration of chlorides at the Olga Plant is 103 mg/l.  Average salinity in the estuary changed little 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)

8.12

8.85

Rt. 31 Bridge

7.83

9.05

I-75 Bridge

8.11

11.97

Ft. Myers Yacht Basin

13.30

16.44

Cape Coral Bridge

22.52

24.14

Shell Point

29.47

30.57

 

Salinity conditions throughout the system are good seaward of Cape Coral.  Conditions in the upper estuary are poor.

 

Water Conservation Areas

 

Water depths decreased by 0.41’ and 0.15’ in WCA-2A and WCA-2B, respectively.  Water depth changes in other WCA impoundments did not change appreciably.  Water depths averages for WCA impoundments all exceeded 1.3’ with highest average depths occurring in WCA-2B (3.3’).  Stages in WCA-1 are within Zone A2, WCA-2A remains well above regulation, and stages in WCA-3 below regulation.


Everglades National Park

 

Rainfall totals were moderate across Everglades National Park (ENP) and FL Bay last week.  Wetland stations where data was available (many stations was not recording) received between 0.75 – 1.1” of rainfall.  The weekly RAINDAR basin-wide spatial averages were ~ 0.4” for the ENP basin and just higher at 0.9” to the east in the C-111 basin, in close agreement with the few stations from which we did receive data last week.

ENP wetland water levels displayed mixed trends.  Water levels both at Shark River Slough (P33) and at the southeastern end of ENP in the panhandle (EVER6) were nearly unchanged (up by 0.2”, down by 0.1”, respectively).  Taylor Slough Bridge saw a modest stage increase (for this station) of 0.8” over the week.  Craighead Pond water level dropped by 0.7”.  These water levels are generally above where they were this time last year, with the exception of P33 which continues to be well below average.

 

Salinity remained generally low and stable across FL Bay, with the exception of a brief reversal at the end of the week just prior to the passage of the weekend cold front.  Strong flow from the Everglades down to the Bay through both Trout Creek and Taylor River allowed salinity to remain in the single digits for much of the 7 day period, with the exception of a brief reversal Friday-Saturday in which salinity shot up (10-20 psu) before dropping back down again.  Salinity in the Taylor River ponds remained below 1 psu over the entire week.  Salinity concentrations at the Little Madeira Bay mouth platform actually dropped into single digits early last week before increasing back into the teens by the weekend.  In the north-central Bay areas, Terrapin Bay and McCormick Creek remained very low for this time of year, generally below 10 psu (with the exception of a brief flow reversal when concentrations increased into the teens).  In central Florida Bay, Whipray Basin remained well below 30 psu for another week.  In the SRS outflow at Tarpon Bay, salinity remained low near 1 psu for the entire week.  The Bay currently appears to be well buffered in terms of salinity for the dry season.

 

Water Supply

 

Water levels in the upper and lower Kissimmee Basin and Lower West Coast showed continued subtle rebound this week as a result of local rainfall.  Water levels also rebounded in the coastal areas of Lower East Coast over the past week, and they are now near or slightly above their historical averages  Surface and groundwater levels in Water Conservation Areas 1 and 2 are now near or slightly above their historic averages.  Water levels in WCA 3A are still somewhat below their historic averages.  Water levels in the southern-most portion of Dade County are slightly above average historic conditions as a result of local rainfall.

 

Five out of eleven water supply risk measures are in the “high” risk category this week - the projected Lake O Stage (SSM), the Palmer Index for Tributary Conditions and Lower East Coast Service Areas 1, 2 and 3.  Water Conservation Areas 1, 2A and 3A continue to be in the “low” risk category.

 

The CPC Precipitation Outlook and the LOK Seasonal and Multi-Seasonal Net Inflow Forecasts remain at “medium” risk this week.

 

WSE (Lake Okeechobee Regulation Schedule)

 

The current Lake O stage remains in the Water Shortage Management zone and is unlikely to move back into Zone E in the next several months

 

 

CC:   George Horne