MEMORANDUM

 

TO:                      Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:                SFWMD Staff Environmental Advisory Team

 

DATE:                 October 9, 2007

 

SUBJECT:           Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

No regulatory releases to the south or estuaries are recommended.

 

Background

 

Drier this week.  Drier air is moving over the District from the northeast and this should dramatically decrease daily shower coverage beginning today.  Showers that do develop will be focused east and south each day this week.  A low pressure system currently in the northwest Caribbean is forecast to pass to our south ahead of an approaching cold front Friday.  This system would need to push further north into the eastern Gulf of Mexico during the coming week than is currently forecast in order for it to produce significant rainfall over the District.  The next ten days precipitation outlook is near average with low confidence.

 

Kissimmee Watershed

 

The upper Kissimmee Basin received 1.97 inches of rainfall over the last 7 days to bring the 130 day total to 28.26 inches (100% of average) and the lower basin received 1.10 inches to bring the total for the last 130 days to 27.20 inches (102% of average).  In most of the upper basin lakes, stage has risen approximately 0.3 feet in the last seven days.  Approximately 250 cfs continues to be released from Lake Tohopekaliga (S-61) and is being held in Lakes Cypress, Hatchineha, and Kissimmee.

 

Flow has been reestablished to the Kissimmee River for 82 days (S-65 re-opened on 07/18/07). Discharge at S-65 continues at approximately 500 cfs.  In the channel of the Kissimmee River, dissolved oxygen sensors have been repaired.  Mean daily concentrations of dissolved oxygen have been 3.25 mg/L to 4.4 mg/L.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 10.11’ NGVD, which is 0.26’ higher than a week ago and 0.52’ higher than a month ago.  The current stage is 3.12’ lower than it was a year ago and remains 5’ below its historical average for this time of year.  Total surface inflows are 1643 cfs and include discharges through the S65E, S84, and S191 structures.  This total does not include gravity flows that might be occurring through the S77 and S308 structures.  No surface outflows are reported.

 

Monthly submerged-aquatic-vegetation (SAV) monitoring was completed during the past week.  SAV was present at 21 of 32 sites sampled across the southern and western sides of the lake.  The macroalga Chara continues to be the dominant SAV, although the vascular plant Vallisineria is being found with increasing frequency.  No algal blooms were observed during this sampling.  The latest monitoring data support a continued trend of increasing water clarity and SAV abundance, declining phosphorus concentrations, and a near-absence of severe algal blooms in nearshore areas of the lake during the past year.

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)

0.3

0.4

 

HR1 (N. Fork)

0.3

0.4

 

Roosevelt Bridge

0.9

1.0

8.0 – 25.0

A1A Bridge

6.8

16.1

20.0 – 31.0

 

Rainfall and associated local runoff lowered average salinity throughout the estuary last week.  Average salinity for the week was below the preferred at the Roosevelt and A1A Bridges. Based on the salinity tolerances of the oyster, Crassostrea virginica, salinity conditions in the estuary are poor.

 

Caloosahatchee Estuary

 

Discharge at S-79 averaged 188 cfs over the past week.  The concentration of chlorides at the Olga Plant is 76 mg/l.  Average salinity increased slightly throughout the estuary last week.  Data for specific sites are given below in parts per thousand (ppt). The Ft. Myers site is being repaired.

 

 

Weekly Average Salinity (ppt)

Sampling Site

Surface

Bottom

Franklin Locks (S-79)

4.7

4.7

Rt. 31 Bridge

3.6

4.9

I-75 Bridge

3.5

6.6

Ft. Myers Yacht Basin

NA

NA

Cape Coral Bridge

17.13

23.1

Shell Point

26.7

28.1

 

Salinity conditions throughout the system are good.

 

FWRI reports that no Karenia brevis, the Florida red tide organism was detected this week in alongshore samples collected between Pinellas and Collier counties.  Additional offshore samples collected 3 to 33 miles west of Sarasota County contained K. brevis concentrations ranging from not present to very low.

 

Water Conservation Areas

 

The lack of rain, relative to evaporation, lead to poor re-hydration rates in WCA-3A, 3B, and NE Shark River Slough.  Decreasing water levels at these locations ranged from -0.04 ft/wk to -0.45 ft/wk in central 3A.  Increasing water levels occurred in the northern regions and averaged +0.25 ft/wk.  Water depths remain good for this time of year because all locations have at least 1.0 ft of water.  Stages in WCA-1 are no longer in Zone A2 and are now at Regulation.  Stages in WCA-2A are almost 1 ft above regulation and stages in WCA-3 are still below regulation.


Everglades National Park

 

Everglades National Park (ENP) wetland water levels increased as a result of last week’s rain event on Oct 1st.  In some areas, though, these water level increases were substantially less than one would expect given the high rainfall totals, suggesting a significant movement of flow downstream (assuming ET has changed little over recent weeks).  Taylor Slough Bridge represented the exception to this trend, increasing by another 8.5” (after last week’s 7” increase) having received just over 3” of rain for the 7 day period (recharge fueled in part by pumping from upstream structures).  A similar amount of precipitation fell over the week in Shark River Sl. (P33), where water level was up by just over 2.75” (enough to account for some weekly evaporation).  In southern Taylor Slough (CP) & the panhandle (EVER6), increases in stage were relatively lower: 0.5” & 1.7”, respectively.  Last week’s releases from S197 into Manatee Bay could explain this discrepancy in the panhandle stage vs. rain.

 

Due to rainfall and strong discharge moving out of the coastal creeks toward Florida Bay, salinity dropped across much of the system again last week.  In one month’s time salinity has declined by an impressive 7 – 20 psu in the eastern and central Bay, providing an important buffer for the upcoming dry season.  Salinity concentrations at both Trout Creek and Taylor River mouth platforms held at or near single digits throughout the week.  Little Madeira Bay saw declining salinity for the week, into the lower-teens by the weekend.  Salinity in the TR ponds remained very low at between 0 – 1 psu.  In the northcentral Bay areas of Terrapin Bay and McCormick Creek salinity dropped to 11 – 12 psu (this area in particular has experienced significantly declining salinity concentrations over recent weeks).  Whipray Basin saw another week of declining salinity, down to 33 psu by Sunday, 10/7.  In the SRS outflow at Tarpon Bay, salinity declined to ~ 4 psu after last week’s brief flow reversal that increased salinity to 10 psu.

 

Water Supply

 

Water levels in the upper and lower Kissimmee Basin (KB) and Lower West Coast (LWC) continue to remain near low levels for their periods of record, with an overall increase in the KB and a slight decline from last week in the LWC.  Water levels improved to the highest percentile in the Upper East Coast and many areas in the Lower East Coast (especially Miami-Dade County) due to recent rainfall, although there was a slight decline in water levels in the LEC over the past week.  Surface and groundwater levels in Water Conservation Areas are now near or above their historic averages.

 

The short-term WSE tributary indices indicate the regions north of the lake have improved. The 30-Day Net Rainfall has risen in the past two weeks and is in the wet range. The Two-Week Moving Average S65E Flow is in the normal range after two weeks of above-average rainfall. However, the long-term Palmer Drought Severity Index (PDSI)* as of 10/06/2007 indicates that the tributaries north of the Lake are still somewhat dry.

 

Four out of eleven water supply risk measures are in the “high” risk category this week – an improvement from last week – including the projected Lake O Stage (SSM), and Lower East Coast Service Areas 1, 2 and 3 (by virtue of being under water restrictions).  The LOK Seasonal forecast and Palmer Drought Severity Index are at “medium” risk.  Water Conservation Areas 1, 2A, and 3A, the CPC Precipitation Outlook, and the LOK Multi-Seasonal Forecast are at low risk.


 

The water level in Lake Istokpoga has declined to below the floor of the schedule, and the SFWMD is initiating the process of requesting a deviation from the current regulation schedule.  Some of the water users in that basin have initiated requests to install “emergency supply wells” to supplement their expected demands over the next year.  An executive order was issued by SFWMD ceasing withdrawals from Lake Istokpoga for consumptive uses.

 

 

WSE (Lake Okeechobee Regulation Schedule)

 

The current Lake O stage – at 10.11’ 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