MEMORANDUM

 

TO:            Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:      SFWMD Staff Environmental Advisory Team

 

DATE:       November 20, 2007

 

SUBJECT: Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

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

 

Background

 

Scattered showers this weekend.  Northeast to east winds will bring widely scattered light showers east today.  As high pressure currently near South Carolina moves southward, expect shower activity to decrease Wednesday.  A cold front is forecast to move into central Florida and stall Thursday night and Friday bringing scattered shower activity mainly north before returning north Saturday.  The next ten days precipitation outlook is below average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received 0 inches of rainfall to bring the 30 day total to 2.17 inches (83% of the long-term average) and the lower basin received 0 inches to bring the 30 day total to 1.65 inches (69% of the long term average).  During the last week, water levels in most of the upper basin lakes decreased slightly or remained steady.  Water levels in Lake Kissimmee, Hatchineha and Cypress increased by 0.1 feet.  The only releases being made in the upper basin are at S-65.  Discharge at S-65 is approximately 250 cfs.

 

Flow has been reestablished to the Kissimmee River for 118 days (S-65 re-opened on 07/18/07).  In the river channel of the Kissimmee River, the concentration of dissolved oxygen ranged from 5.9 – 8.0 mg/L (mean 7.0 mg/L) during the past week.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 10.32’ NGVD, which is 0.01’ lower than a week ago and 0.16’ higher than a month ago.  The current stage is 2.07’ lower than it was a year ago and remains almost 5’ below its historical average for this time of year.  Total reported surface inflows of 905 cfs are similar to last week and include flows from the Kissimmee River (250 cfs) and the L8 at Canal Point (655 cfs).  No outflows are reported.  

 

Near shore areas of the lake continue to experience moderate turbidity in response to windy conditions.  Beds of the macroalga Chara are declining in offshore areas on the south side but appear to be stable closer to shore.  Beds of the vascular species eelgrass (Vallisneria americana) are expanding but generally are being found in locations with about 1’ of water that likely will go dry within the next few months.  Okeechobee Division staff participated in a meeting with the FWC and USACE last week to discuss the feasibility of planting vascular SAV at selected locations in the lake next wet season to augment the natural recovery of these species following previous years’ hurricanes and the current drought.    


St. Lucie Estuary

 

There were no releases through S-80 over the past week.  Discharge at S-97 on the C-24 Canal is currently 0 cfs.  Discharges at S-49 on the C-23 canal are currently about 4 cfs.  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)

4.28 (2.5)

5.69 (2.9)

 

HR1 (N. Fork)

8.06 (7.3)

11.02 (10.3)

 

Roosevelt Bridge

11.04 (9.7)

12.34 (12.1)

8.0 – 25.0

A1A Bridge

18.40 (17.9)

24.34 (24.4)

20.0 – 31.0

 

Salinity conditions improved this week throughout the estuary.  Both the surface and bottom salinity are now up to the preferred range at the Roosevelt Bridge, but still only the bottom salinity is in the preferred range at the A1A Bridge.  Based on the salinity tolerances of the oyster, Crassostrea virginica, salinity conditions in the estuary are good-fair.

 

Caloosahatchee Estuary

 

No discharge occurred at S-79 last week.  The concentration of chlorides at the Olga Plant is 144 mg/l.  Average salinity increased throughout the estuary last week.  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)

13.3 (10.9)

14.0 (12.3)

Rt. 31 Bridge

12.0 (10.2)

14.0 (13.7)

I-75 Bridge

12.0 (10.5)

14.6 (14.2)

Ft. Myers Yacht Basin

17.1 (15.4)

18.4 (17.1)

Cape Coral Bridge

22.8 (22.3)

25.1 (24.5)

Shell Point

30.3 (30.0)

31.5 (30.9)

 

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

 

FWRI reports that water samples collected offshore this week, 7 to 25 miles west of Collier County, detected Karenia brevis, the Florida red tide organism, at concentrations ranging from not present to very low.  Alongshore samples collected between Pinellas and Collier counties contained no K. brevis.

 

Water Conservation Areas

 

Rainfall throughout the WCAs was negligible (i.e., 0.08” – 0.02”). Average precipitation for the Greater Everglades was only 0.04 inch. This was another week with a deficit water budget because ET was 1.11

 

Dry season recession rates now predominate the entire region but not as much as they did last week. Water depths decreased by 0.15’ in WCA-1, 0.12’ in WCA-2A, 0.16’ in northern WCA-3A, 0.11’ NESRS, but only by 0.04’ in WCA-3B and central WCA-3A. Water depths are typically between 2-3 ft, at this time of year, in the WCAs. However, WCA-1, 2A and WCA-3A are just barely above 2.0 ft. In northern WCA-3A, where drought impacts are expected to be severe this spring, the depths are similar to the drought of last year and about 1.25 ft less than in 2005. However, the wet season depths last year were greater and provided for better fish habitat. Therefore, wading bird prey populations will likely be worse than they were last year.

 

Stages in WCA-1 are about to enter within Zone B, WCA-2A remains well above regulation, and stages in WCA-3 remain below regulation.

 

Everglades National Park

 

ENP wetland water levels declined last week.  Water level at Shark River Slough (P33) was down by 0.2”, but remains low for this time of year.  To the south, water levels declined by 1.2 and 2.3” at Craighead Pond and EVER6, respectively, and Taylor Slough Bridge declined by 5.6” over the 8 d period.

Salinity managed to concurrently increase, decrease, and/or remain stable across FL Bay last week.  At Trout Creek, salinity was quite variable throughout the week, flashing (almost daily) from single digits up to the low 20s, but ultimately increasing to near 25 psu by week’s end.  A similar trend occurred at Taylor River mouth with salinity settling at 11 psu by week’s end.  Flow reversals did not make their way far upstream, however, as salinity in the Taylor River ponds remained below 1 psu for the entire week.  Salinity concentrations at the Little Madeira Bay mouth platform remained stable in the mid-teens throughout the week.  In the north-central Bay areas, salinity declined to under 10 psu in Terrapin Bay.  McCormick Creek saw an early week reversal (mid-teens), but dropped to under 9 psu by week’s end.  In central FL Bay, Whipray Basin remained steady below 30 psu for another week.  In the SRS outflow at Tarpon Bay, salinity decreased slightly to below 3 psu.  As of now, FL Bay salinity is continuing to remain low and apparently well buffered at this stage of the dry season.

Water Supply

 

Water levels in the upper and lower Kissimmee Basin and Lower West Coast declined slightly this week – and are now slightly below their historical average conditions for this time of year.  Water levels in the coastal areas of Lower East Coast are still 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 continue to remain below their historic averages – and were somewhat lower this week.  Water levels in the southern-most portion of Dade County are slightly above average historic conditions as a result of local rainfall.  

 The Water Supply Risk Measures were unchanged this week.  Six out of eleven water supply risk measures are in the “high” risk category - the projected Lake O Stage (SSM), the Palmer Index for Tributary Conditions, the LOK Seasonal Net Inflow Forecast 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 Multi-Seasonal Net Inflow Forecasts remain at “medium” risk this week.

 

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.

 

 

CC:   George Horne