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 20, 2008

 

SUBJECT:         Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

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

 

Background

 

Daily shower activity is forecasted this week.  A weakening frontal boundary across central Florida is tapping decent moisture over the area to generate scattered showers today focused north and east each day.  The old front will become more diffuse on Wednesday so afternoon shower and thunderstorm coverage will decrease a bit.  Activity should remain focused north and east Saturday.  Building high pressure should bring a return of drier conditions by Monday.  The next ten days precipitation outlook is below average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received 0.02 inches of rainfall to bring the 30 day total to 0.15 inches (5% of average), and the lower basin received 0.01 inches to bring the 30 day total to 0.08 inches (3% of average).  Releases from East Lake Tohopekaliga (S-59) continued at 180 cfs.  Releases from Lake Tohopekaliga (S-61) ceased today.  Releases from the Alligator Chain (S-60) ceased.  Releases from Lake Gentry decreased to 60 cfs.  Releases from Lake Kissimmee (S-65) continued at 400 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 300 days (S-65 re-opened on 07/18/07).  With the decreased inflow from the upper basin, water levels continue to decline across the Kissimmee River Restoration Project.  The water level at Weir 3, near the upstream end of the Phase I area, has fallen about 0.75 ft in the last week to 37.03 feet.  The headwater stage at S-65C has decreased 0.49 feet to 33.97 feet, so that the water surface elevation decreases by 3.06 feet from the upstream end to the downstream end of the restoration project.

 

Dissolved oxygen data are currently unavailable due to technical difficulties.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 9.78’ NGVD, which is 0.20’ lower than a week ago and 0.66’ lower than a month ago.  The current stage is 0.48’ higher than it was a year ago and 3.53’ below its historical average for this time of year.  Reported inflows include ~250 cfs from the Kissimmee River.  Outflows include 417 cfs through the S352 and 112 cfs through the S77.

 

A muck burial demonstration project was completed last week in the lake’s littoral zone adjacent to the Indian Prairie Canal.  Four different tilling and disking methods are being tested for their ability to sequester soil phosphorus and improve vegetation conditions.  A total of 40 acres have been treated.  Pre- and post-treatment sampling was conducted to measure effects on soil phosphorus retention and the plant seed bank.

 

Wildfires continue to burn in the littoral zone in the southwest corner of the lake.  Approximately 26,000 acres have now burned.  The Grassy Island fire is completely contained.  The Myakka Cut fire is 50% contained but continues to spread actively to the east-northeast.  Three smaller wildfires (<100 acres total) have been reported along the western shore and all but one of these has been contained.

 

St. Lucie Estuary

 

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

19.24 (16.60)

20.81 (17.99)

 

HR1 (N. Fork)

20.62 (18.26)

22.85 (20.64)

 

Roosevelt Bridge

22.95 (17.82)

24.22 (19.88)

8.0 – 25.0

A1A Bridge

30.30 (26.98)

31.83 (30.19)

20.0 – 31.0

 

Average salinity increased about 3 ppt in North Fork and South Fork, 5 ppt at Roosevelt Bridge, and 2-4 ppt at A1A Bridge.  Both the surface and bottom salinity are in the preferred range at the Roosevelt Bridge.  The bottom salinity at A1A Bridge exceeded 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 of 23 ppt at the Roosevelt Bridge is 5 ppt 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 184 cfs occurred at S-77and 102 cfs at S-78.  The concentration of chlorides at the Olga Plant was 237 ppm yesterday, down from 276 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)

16.74 ( 14.97)

17.25 (15.73)

Rt. 31 Bridge

17.67 (17.52)

18.67 (17.79)

I-75 Bridge

18.64 ( 18.60 )

20.08 (19.23)

Ft. Myers Yacht Basin

24.41 (23.60)

24.56 (23.70)

Cape Coral Bridge

31.47 (30.73)

32.13 (31.10)

Shell Point

35.67 (35.38)

36.38 (36.08)

 

Average salinities increased about 1 ppt throughout the estuary.  Salinity at the Ft. Myers surface sensor was 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

 

As in past weeks, recession rates were high in almost all the WCAs due to the lack of rain and high evapotranspiration, and water depths are now declining to depths that are fair to good for wading bird foraging over much of the conservation areas.  In some regions the recessions were actually a little too high but this is not a concern given water depths are in general at the high end of wader foraging ranges, especially in WCA-3A and 3B.  Stages throughout the WCA’s continue to decline and are above Regulation in WCA-2A, at regulation in WCA-1 and below regulation inWCA-3A.

 

Everglades National Park

 

Little rainfall & high evapotranspiration (ET) caused water levels to decline across Everglades National Park (ENP) wetlands last week.  Water levels dropped by 4.4” at Taylor Slough Bridge and by nearly 3” in the southern part of Taylor Slough (at Craighead Pond).  At the panhandle station @ EVER6, water levels were down substantially, by just over 2.75”.  Shark River Slough (station P33, where no rainfall was measured last week) declined only 0.3”.

 

Salinity rose across much of Florida Bay last week due to strong southerly winds and high rates of evaporation.  Concentrations herein described should be near their seasonal peaks, unless the rains don’t kick in soon.  Salinity rose slightly in the northeast Bay, into the upper 30s at Trout Creek and Long Sound/Highway Creek, and toward the middle-30s at the mouth of 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 the entire week.  As of Sunday, 5/18, the 30 day moving average concentration at TR (used for tracking the FL Bay MFL criterion) was at 28.2 psu (up from 24.6 psu last week); with concentrations already over 30 psu for 11 days straight, and sustained high temps & ET, it is possible that we will exceed the 30 psu salinity criterion this dry season at TR.  Salinity rose near 40 psu in the north central Bay areas of McCormick Creek and Terrapin Bay.  At the central Bay station in Whipray Basin salinity moved into the lower-40s.  Salinity in the upstream reaches of Shark River (Tarpon Bay platform) measured slightly above the seasonal norm (mid-teens), holding near 20 psu.

 

Water Supply

 

Last week was dry again, so most water levels decreased across the District.  Water levels in the upper and lower Kissimmee Basin are now near or 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 now near their historic averages although they declined this past week.  Surface and groundwater levels in Water Conservation Areas 1, 2 and 3 are now near or slightly above their historic averages – although they have been declining steadily over the past week.  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