MEMORANDUM

 

TO:                      Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:                SFWMD Staff Environmental Advisory Team

 

DATE:                 October 16, 2007

 

SUBJECT:           Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

No regulatory releases to the south or estuaries are recommended.

 

Background

 

Mini-wet season returns for about 5 days.  Deeper moisture just to our south and east will begin to envelop the District today as high pressure moves into the southwest Atlantic.  Look for the resulting southeast winds to focus showers along the Lower East Coast this afternoon through overnight.  Steering flow becomes more southerly on Wednesday, and this vector will provide a better chance for rains over the Kissimmee Valley.  More moisture is likely to arrive Thursday or Friday ahead of a cold front, so look for above average rains through Saturday before significant drying begins north to south on Sunday.  The next ten days precipitation outlook is near average with low confidence.

 

Kissimmee Watershed

 

The upper Kissimmee Basin received 0.06 inches of rainfall over the last 7 days to bring the 30 day total to 6.25 inches (137% of average) and the lower basin received 0.07 inches to bring the total for the last 30 days to 4.71 inches (106% of average).  (Daily Rainfall Report for 10/15/07).

The upper basin lakes are all below the regulation schedule.  Stage in Lake Toho has increased 0.9 ft in the last week and no releases are being made. Snail kites continue to nest on Lake Tohopekaliga (No update since September 21).  Flow has been reestablished to the Kissimmee River for 90 days (S-65 re-opened on 07/18/07).  Discharge at S-65 continues at approximately 500 cfsIn the channel of the Kissimmee River, mean daily concentrations of dissolved oxygen have been 2 mg/L to 3 mg/L. 

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 10.08’ NGVD, which is 0.03’ lower than a week ago and 0.47’ higher than a month ago.  The current stage is 2.99’ lower than it was a year ago and remains 5’ below its historical average for this time of year.  Discharges of 997 cfs through the S65E structure account for all reported inflows to the lake.  Periodic gravity inflows also may be occurring through the S77 and S308 structures.  No surface outflows are reported.

 

During September, water-quality samples were collected from 20 of 27 sampling sites.  TP concentrations lakewide averaged 77 ppb compared to 85 ppb in August.  However, TP concentrations in nearshore areas across the southern and western sides of the lake averaged only 33 ppb, with concentrations as low as 11 ppb at some sites.  Water clarity in nearshore areas continues to be excellent as well.

 

Efforts are ongoing to assess the feasibility of reintroducing apple snails to the lake’s littoral zone following reflooding.  This species, which is the exclusive food source for the endangered snail kite, is especially sensitive to drought conditions and may be unable to recover quickly by natural means.  During October, approximately 400 apple snail eggs were transported from Lake Kissimmee to a facility at Harbor Branch where they will be used to compare alternative methods for mass-rearing snails in a hatchery environment.

 

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)

0.5

0.5

 

HR1 (N. Fork)

NA

0.5

 

Roosevelt Bridge

2.81

3.26

8.0 – 25.0

A1A Bridge

12.81

21.61

20.0 – 31.0

 

Average salinity increased at both the Roosevelt and A1A Bridges last 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 53 cfs over the past week.  The concentration of chlorides at the Olga Plant is 80 mg/l.  Average salinity increased throughout the upper estuary last week but changed little at Cape Coral and Shell Point.  Data for specific sites are given below in parts per thousand (ppt). The Ft. Myers site is back on-line.

 

 

Weekly Average Salinity (ppt)

Sampling Site

Surface

Bottom

Franklin Locks (S-79)

7.5

7.8

Rt. 31 Bridge

6.0

7.4

I-75 Bridge

5.9

8.6

Ft. Myers Yacht Basin

11.9

13.3

Cape Coral Bridge

17.6

20.6

Shell Point

26.5

28.5

 

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

 

FWRI reports that no Karenia brevis, the Florida red tide organism was detected this week in alongshore samples collected between Pinellas and Monroe counties. Additional samples collected offshore of Pinellas and Manatee counties, as well as the Florida Keys, contained no K. brevis.


Water Conservation Areas

 

The lack of rain, relative to evaporation, lead to poor rehydration rates for a second week, especially in WCA-1, where water levels declined by 0.15 ft.  However, WCA-3A and WCA 2B water levels did not recede due to release of waters from WCA-2A.  Despite this release, water levels in WCA-2A remained well above regulation.  Water depths remain good for this time of year because all locations have at least 1.0 ft of water.  The fires that were reported on Oct 10th along the L-67 levees in WCA-3B did not appear to be muck burns because of these depths.  Stages in WCA-1 are no longer in Zone A2 and are now at Regulation. Stages in WCA-3 are again slightly below regulation.

 

Everglades National Park

 

Everglades National Park (ENP) wetland water levels decreased.  Stations in the south saw appreciable decreases such as,  -0.35 ft  at Taylor Slough Bridge, -0.11 ft in the ENP panhandle (EVER6), and -0.16 ft at Craighead Pond over the 7d period.

 

Despite lower overall rainfall last week, salinity continued to decline or remain stable across Fl Bay.  Significant flow through both Trout Creek & Taylor River allowed salinity to remain very low (in single digit concentrations) all week.  Salinity in the TR ponds remained steady at or below 1 psu all week.  To the south, Whipray Basin salinity dropped below 30 psu for the first time this wet season.  In the past month the 7 day moving average salinity in Whipray Basin has declined 10 psu (from 41 psu on 9/14 to 31 psu).  This pronounced decline in Baywide salinity over recent weeks may provide an important buffer heading into the dry season.  In the SRS outflow at Tarpon Bay, salinity remained at or below 3 psu over the week.

 

Water Supply

 

Water levels in the upper and lower Kissimmee Basin and Lower West Coast showed some rebound this week and there was some continued recovery in shallow wells in the LWC and UEC 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 the 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 are still in the high risk category.

 

Water Conservation Areas 1, 2A and 3A continue to be in the “low” risk category.  The CPC Precipitation Outlook and the LOK Multi-Seasonal Net Inflow Forecast remain at “low” risk this week, and the LOK Seasonal Inflow forecasts are at “medium” risk.

 

WSE (Lake Okeechobee Regulation Schedule)

 

The current Lake O stage – at 10.08’ 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