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 18, 2007

 

SUBJECT:                   Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

No regulatory releases to the south or estuaries are recommended.

 

Background

 

Above average rains this week with widespread moderate to heavy rains possible tomorrow and Thursday.  An upper level trough is digging into the Florida peninsula this morning.  This scenario will aid the development of a nontropical low just off the coast today that will then migrate westward across the peninsula tonight and into the extreme eastern Gulf of Mexico tomorrow.  Then, tropical development is possible as this low moves westward through the Gulf on Thursday.  This is good news from a hydrologic viewpoint as areas of heavy rainfall are likely during this evolution.  Look for locally heavy rains to 4" near the east and south coasts today through tonight.  Heavier rains are more likely to envelop interior areas of the District tomorrow and Thursday.  The next ten days precipitation outlook is above average with moderate confidence.

 

Kissimmee Watershed

 

The upper Kissimmee Basin received 0.83 inches of rainfall over the last 7 days to bring the 30-day total to 3.77 inches (58% of average) and the lower basin received 1.30 inches to bring the 30-day total to 4.55 inches (74% of average) (Daily Rainfall Report for 09/17/07).

 

Stages in most of the upper basin lakes have been stable over the last seven days.

 

Snail kites continue to nest on Lake Tohopekaliga.  Flow has been reestablished to the Kissimmee River for 62 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 3 mg/L for most of the previous week.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 9.65’ NGVD, which is 0.08’ higher than a week ago and 0.13’ higher than a month ago.  The current stage is 3.77’ lower than it was a year ago and remains approximately 4’ below its historical average for this time of year.  Reported surface inflows are 1003 cfs compared with 1039 cfs last week.  These values do not include gravity inflows through the S77 (not reported) and S308 (not reported) structures.  No surface outflows are reported.

 

Monthly algal bloom monitoring was conducted on the 12th of September.  Four of the 10 monitoring sites were dry and 1 site was not sampled due to boat problems.  An algal bloom was present at 1 of remaining 5 survey sites.  Water quality data from this trip will be available later in the month.

 

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)

8.7

10.1

 

HR1 (N. Fork)

9.4

13.1

 

Roosevelt Bridge

14.9

15.2

8.0 – 25.0

A1A Bridge

21.9

26.4

20.0 – 31.0

 

Salinity at the Palm City Bridge increased during the past week.  Elsewhere, salinity declined slightly.  Local freshwater inflow continues to maintain salinity at both the Roosevelt Bridge and A1A Bridge within the preferred ranges.  Therefore, salinity conditions in the estuary are good.

 

Caloosahatchee Estuary

 

During the past week, discharge at S-79 averaged 187 cfs.  Chloride concentration at the Olga Plant is presently 77 mg/l.  Average salinity at the monitoring sites in the lower Caloosahatchee Estuary decreased slightly 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)

6.4

6.5

Rt. 31 Bridge

NA

7.1

I-75 Bridge

6.2

9.4

Ft. Myers Yacht Basin

13.0*

NA

Cape Coral Bridge

18.0

18.5

Shell Point

28.5

33.3

* based on two-day average.

 

Salinity in the upper estuary remains high for this time of year.  The 30-day average surface salinity at Ft. Myers is 11.7 ppt.  Conditions in the upper estuary are fair.  Downstream of the Cape Coral Bridge salinity conditions are good.

 

During a field trip on Sept. 12, dispersed blue green algae were observed upstream of S-79.  None were noted in the downstream estuary.  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.  However, patchy areas of very low concentrations were found offshore of Sarasota, Lee and Collier counties.

 

Water Conservation Areas

 

Water depths are similar to last week’s, ranging from 0.41’ in WCA-3A to 2.77’ in WCA-2B.  Most water depths are 1’ to 1.6’ in the WCAs, which are 0.5’ to 1’ below last year’s at this time. 

 

Stages rose somewhat in WCA-1, decreased slightly in WCA-2A and 2B, and remained overall about the same in WCA-3A.  They dropped a steep -0.24’ in WCA-3B (Site 76) but rose 0.11’ in Northeast Shark River Slough.  WCA-1 is still within Zone A2, WCA-2 is just below regulation, and WCA-3A is approximately 1’ below regulation.

 

Everglades National Park

 

Water levels across Everglades National Park (ENP) wetlands were generally up again last week.  Water levels rose impressively in Shark River Slough (station P33) after 3.5” inches of rain produced just over a 2” rise.  A similar increase at Taylor Slough Bridge (up by 2.5”) occurred but is more common in this part of the system.  Craighead Pond (CP) water levels also rose 1.8”.  Water levels fell only in the ENP panhandle (station EVER6), where light weekly rainfall (~ 0.1”) could not offset high rates of ET.

Salinity either changed little or declined slightly across Florida Bay last week.  Trout Creek salinity decreased throughout the week to just below 10 psu at the end of the weekend.  At the platform at the mouth of Little Madeira Bay, salinity remained near 20 psu.  It was very low at the Taylor ponds, under 1 psu at Argyle Hendry, Taylor River, and Pond 5.  Reported salinity in the north-central Bay areas of Terrapin Bay and McCormick Creek dropped last week, from the mid-30s early in the week to below 30 psu by the weekend (approaching 20 psu at McCormick Creek).  In the central Bay, Whipray Basin salinity stayed near 41 psu for another week.  To the north and west, Tarpon Bay (Shark River Slough outflow) salinity remained low, between 2 – 3 psu.

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 – although there was some recovery in shallow wells in the LWC this week as a result of local rainfall.  Water levels continued to declined slightly in the coastal areas of the Upper East Coast and Lower East Coast over the past week, but they remain near or 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.  Water levels in the southern-most portion of Dade County rebounded somewhat, as a result of local rainfall.

 

Six out of eleven water supply risk measures are in the “high” risk category this week – no change from last 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 and 2A continue to be in the “low” risk category and Water Conservation Area 3A is now at “medium” risk.  The CPC Precipitation Outlook remains at “low” risk this week, and the LOK Seasonal Net Inflow forecast is now at “medium” risk.

 

WSE (Lake Okeechobee Regulation Schedule)

 

The current Lake O stage – at 9.65’ 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