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:       May 27, 2008

 

SUBJECT:         Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

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

 

Background

 

Mainly dry for the next couple of days before rains increase south the end of the week.  Deep layered high pressure will dominate the skies over the peninsula for most of the business week.  Decent moisture will return south of the Lake to aid seabreeze showers/storms as early as Thursday, but it will take until the weekend before widespread rains return.  In fact, there is good evidence from a few different models that rains could become heavy in about 6-7 days.  The next ten days precipitation outlook is near average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received 0.03 inches of rainfall, and the lower basin received 0.04 inches inches (Daily Rainfall Report 5/12/08).

 

During the last week, releases from the upper basin lakes were adjusted to allow water levels to decline with the regulation schedules.  Releases from East Lake Tohopekaliga (S-59) decreased to 176 cfs.  No other released are being made currently in the upper basin as lake stages approximate their respective regulation schedules.

 

Releases from Lake Kissimmee (S-65) were decreased from 500 cfs to 220 cfs.

 

In the upper basin, snail kites continue to nest on East Lake Toho, Lake Toho, and Lake Kissimmee.  Nests on Lake Toho continue to represent a large fraction of the total number of snail kite nests in Florida.

 

Flow has been reestablished to the Kissimmee River for 307 days (S-65 re-opened on 07/18/07).  Flow is approximately 220 and250 cfs at S65 and at S-65C, respectively.

 

With the decreased inflow from the upper basin, water levels continue to decline across the Kissimmee River Restoration Project.  The headwater stage at S-65C has decreased to 33.61 feet.   Dissolved oxygen concentrations in the river channel of the Kissimmee River exceed the range of concern and average approximately 5.0 mg/L.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 9.76’ NGVD, which is 0.02’ lower than a week ago and 0.60’ lower than a month ago.  The current stage is 0.70’ higher than it was a year ago and 3.48’ below its historical average for this time of year.  Reported inflows include 744 cfs from the Kissimmee River.  Reported outflows include 141 cfs through the S77.  Outflows also are occurring through temporary forward pumps at S351 and S354, but discharge volumes are not reported on the web site.

 

Monthly phytoplankton monitoring was performed on May 22.  Six of nine sites had sufficient water for sampling.  Mean secchi depth was 0.28 m (compared to 0.45 m in April).  Chlorophyll data are not yet available, but bloom conditions were not observed at any of the stations.

 

All 5 wildfires burning in the lake’s littoral zone are nearly or fully contained and only one at Lakeport near Fisheating Creek is expanding.  Conditions were improved by rainfall in this area over the last several days.  Approximately 26,000 acres have burned.

 

St. Lucie Estuary

 

There were no releases through S-80 from C-44 and S-48 from C-23 over the past week.  The flow values from S-49 from C-24 were unavailable.  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)

18.89 (19.24)

20.14 (20.81)

 

HR1 (N. Fork)

21.67 (20.62)

22.90 (22.85)

 

Roosevelt Bridge

NR (22.95)

NR (24.22)

8.0 – 25.0

A1A Bridge

29.49 (30.30)

30.42 (31.83)

20.0 – 31.0

 

Average salinity increased slightly at HR1 and decreased slightly at Palm City Bridge and A1A Bridge.  Salinity values were unavailable at Roosevelt Bridge all week.  However, it can be reasonably assumed that average salinity at Roosevelt Bridge, like the other stations, did not change much over the last week.  The salinities at A1A Bridge are just within the upper limit of the preferred range.  Salinity conditions in the estuary are considered fair, based on the salinity preference of the oyster, Crassostrea virginica, at Roosevelt Bridge.  The current surface salinity at Roosevelt Bridge is unavailable but should still be below the maximum weekly average of 28.0 ppt achieved in May 2001 during the 2000 – 2001 drought.

 

Caloosahatchee Estuary

 

No discharge occurred through S-79 during the past week.  An average weekly discharge of 274 cfs occurred at S-77and 131 cfs at S-78.  The concentration of chlorides at the Olga Plant was 248 ppm yesterday, up from 237 ppm in the beginning of this reporting period.  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)

16.71 ( 16.74)

17.47 (17.25)

Rt. 31 Bridge

18.12 (17.67)

19.06 (18.67)

I-75 Bridge

19.44 ( 18.64 )

20.51 (20.08)

Ft. Myers Yacht Basin

24.53 (24.41)

24.77 (24.56)

Cape Coral Bridge

31.89 (31.47)

32.51 (32.13)

Shell Point

35.86 (35.67)

36.51 (36.38)

 

Average salinities increased slightly (< 1 ppt) throughout the estuary.  Average salinity at the Ft. Myers surface sensor was 24.53 ppt, above the 1-day MFL criterion of 20 ppt.  The current surface salinity of 16.7 ppt at S-79 is 3.3 ppt below the maximum weekly average of 20.0 ppt achieved in May 2001 during the 2000 – 2001 drought.  Salinity at Shell Point and the Cape Coral Bridge is above the optimal range for the oyster, Crassostrea virginica.  Conditions in the upper estuary east of Ft. Myers are poor due to high salinity.  Conditions in the lower estuary downstream of Cape Coral are fair considering the combine salinity preference of oysters and seagrasses.

 

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.

 

Water Conservation Areas

 

After some four weeks of good recession rates in support of wading bird nesting, recent rains, especially in the north, have caused water depths to increase by as much as a quarter of a foot. Recession rates were poor or fair almost everywhere and water depths remain above optimum (optimum = 0.1’ – 0.79’) for foraging by wading birds.  Stages increased throughout the WCA’s, but continue to decline in Everglades National Park (ENP).  Stages are slightly above regulation in WCA-1, well above Regulation in WCA-2A and slightly below regulation in WCA-3A.

 

Everglades National Park

 

Rainfall was patchy across ENP and Florida Bay last week, with the 7 day accumulations across the wetland and marine stations measuring between 0.1 – 0.7.  This spatially variable pattern was reflected in last week’s trends for ENP wetland water levels, down across much of the area except in the panhandle where rainfall totals were higher (1 – 2” based on RAINDAR estimates).  Water levels dropped by a meager 0.3” again this week in Shark River Slough (station P33, recording 0.2” of rain for the week), which is not much considering the high temps/ET of late.  Taylor Slough Bridge posted a weekly decline of 1.9” (not an unusual recession rate at this station).  The most dramatic recession was again in the southern part of Taylor Slough (at Craighead Pond), down by nearly 3” for the third straight week.  As mentioned, the panhandle was the only area to show increasing water levels, up by 1.8” at station EVER6.

 

Modest rainfall buffered the persistent strong southerly winds and high rates of evaporation last week, allowing salinity in much of Florida Bay to remain fairly stable.  Concentrations herein described should be near their seasonal peaks, unless the rains don’t kick in soon (in which case salinity will continue to climb).  Salinity held steady in the northeast Bay, reading in the upper 30s at Trout Creek and Long Sound/Highway Creek, and the middle-30s at the mouths of Taylor River and L. Madeira Bay.  In the Taylor ponds, daily mean salinity remained over 30 psu at Pond 5 (USGS station) and Argyle Hendry (ENP station TR) for another week.  As of Sunday, 5/25, the 30 day moving average concentration at TR (used for tracking the FL Bay MFL criterion) was at 30.4 psu (up from 28.2 psu last week).  Low rainfall, strong winds, and high evapotranspiration across the region have facilitated daily mean concentrations exceeding 30 psu for 18 consecutive days at TR, so it is not surprising that we surpassed the 30 day running average criterion of 30 psu on Sat., 5/24.  Salinity held near 40 psu in the northcentral Bay areas of McCormick Creek. & Terrapin Bay.  The central Bay station in Whipray Basin, though, posted a substantial salinity increase last week, up into the mid-40s.  Salinity in the upstream reaches of Shark River (Tarpon Bay platform) measured above the seasonal norm (mid-teens), moving up into the mid-20s last week.

 

Water Supply

 

Although there was some scattered rain last week, most water levels decreased across most of the District.  Water levels in the upper and lower Kissimmee Basin are now slightly below their historical average conditions for this time of year.  Water levels in the Lower West Coast are now near their historical averages, though some water levels (e.g., Sandstone Aquifer) are below those conditions depending on the degree of confinement of the aquifers.  Water levels in the Lower East Coast are near or slightly below their historical averages.  Water levels in the Upper East Coast are still slightly above their historic averages.  Surface and groundwater levels in Water Conservation Areas 1, 2 and 3 are now near their historic averages – although they have been declining steadily over the past few weeks.  Water levels in the southernmost portion of Miami-Dade County are now below their average historic conditions.

 

There was no change in the water supply risk indicators since last week.  Six out of the eleven water supply risk indicator parameters are now in the “low” risk category, including the CPC Precipitation Outlook, the Lake Okeechobee Seasonal and Multi-seasonal Net Inflow Forecast, and Water Conservation Areas 1, 2A and 3A.

 

Four out the eleven water supply risk indicators are now in the “medium” risk category, including the Palmer Index for Tributary Conditions (dry) and the LEC Service Areas 1, 2 and 3.

 

The only risk measure that is in the “high” risk category is the projected Lake Okeechobee Stage (water restriction zone).

 

LORS2008 (Lake Okeechobee Regulation Schedule)

 

The current Lake Okeechobee stage remains in the Water Shortage Management zone and is unlikely to move back into the Operational Band in the next several months during the persistent La Niña climactic conditions.

 

CC:   George Horne