MEMORANDUM

 

 

TO:            Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:      SFWMD Staff Environmental Advisory Team

 

DATE:       April 29, 2008

 

SUBJECT: Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

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

 

Background

 

Scattered showers and storms are south today, then dry and pleasant tonight through Thursday morning.  A cold front made its way to the north shore of Lake Okeechobee at 9 am.  Decent moisture will combine with good heating and incoming upper level support to generate an active afternoon of showers and storms over southern and eastern sections of the District.  Some storms could be quite strong with local rains to 2.5”.  Showers and storms will decrease this evening as the front exits southeastward.  Much drier and slightly cooler air will move in to yield pleasant conditions tonight through Thursday morning.  Look for some increase in temperatures and moisture late in the week with some garbage/weak showers returning as early as Saturday.  The next ten days precipitation outlook is below average with moderate confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received 0 inches of rainfall to bring the 30 day total to 3.61 inches (149% of average), and the lower basin received 0 inches to bring the 30 day total to 3.45 inches (153% of average).  During the last week, releases were increased from East Lake Tohopekaliga (S-59) to 160 cfs and from Lake Tohopekaliga (S-61) to 600 cfs.  Releases from Lake Kissimmee (S-65) were decreased from 1100 cfs to 700 cfs.  No other releases were made in the upper basin last week.  Hydrilla treatment continued in Lake Cypress last week.  The vegetation removal project in Lake Gentry should be completed this week.

 

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 279 days (S-65 re-opened on 07/18/07).  With the decreasing inflow from the upper basin, over-bank flow ended at most locations in the Phase I area of the Kissimmee River Restoration Project.  The floodplain likely will be draining for several weeks.  Dissolved oxygen concentrations in the river channel of the Kissimmee River ranged from 3.6 mg/L to 7.1 mg/L with an average of 5.7 mg/L, which is a slight increase over the last report.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 10.31’ NGVD, which is 0.10’ lower than a week ago and 0.06’ higher than a month ago.  The current stage is 0.62’ higher than it was a year ago and 3.43’ below its historical average for this time of year.  Reported inflows include ~700 cfs from the Kissimmee River.  Outflows include ~270 cfs through the S352 and ~70 cfs through the S77.

 

April water-quality monitoring results are now available.  Seventeen of the 25 monitoring stations had sufficient water for sampling.  Total P averaged 111 ppb lake wide (compared to 141 ppb in March) and 33 ppb at near shore stations (compared to 81 ppb in March).  Total suspended solids (TSS) averaged 35 ppm lake wide (compared to 33 ppm in March) and 6 ppm at near shore stations (compared to 25 ppm in March).

 

Monthly phytoplankton monitoring was performed on April 22.  Six of nine sites had sufficient water for sampling.  Mean secchi depth was 0.45 m (compared to 0.18 m in March).  Chlorophyll data are not yet available, but there was a surface bloom in the Pahokee Marina and evidence of bloom formation at LZ40 (center of the lake).  Samples were collected for taxonomic analysis and a preliminary identification of Microcystis aeruginosa was made by District staff.  Microcystin concentrations were all at or below the analytical limit of detection (0.2 ug L-1) except for the Pahokee Marina sample which was 0.8 ug L-1.

 

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)

13.98 (11.09)

15.26 (12.44)

 

HR1 (N. Fork)

17.57 ( 14.04)

18.77 (16.87)

 

Roosevelt Bridge

16.76 (15.93)

18.95 (18.02)

8.0 – 25.0

A1A Bridge

27.28 (24.66)

29.16 (27.79)

20.0 – 31.0

 

Average salinity increased about 3 ppt in the South Fork and North Fork, and about 1-2 ppt at Roosevelt Bridge and A1A Bridge during the past week.  Both the surface and bottom salinity are in the preferred range at the Roosevelt Bridge, and at the A1A Bridge.  Salinity conditions in the estuary are considered good, based on the salinity preference of the oyster, Crassostrea virginica, at Roosevelt Bridge.  The current surface salinity of 16.8 ppt at the Roosevelt Bridge is 11.2 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 302 cfs occurred at S-77.  The concentration of chlorides at the Olga Plant yesterday was 189 mg/l, slightly up from 186 mg/l of last week.  Weekly average salinities for specific sites are given below in parts per thousand (ppt).  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)

13.77 ( 11.06)

14.64 (11.73)

Rt. 31 Bridge

13.33 ( 10.89)

NA (NA)

I-75 Bridge

NA ( NA )

17.41 (15.01)

Ft. Myers Yacht Basin

21.36 (19.40)

22.23 (20.41)

Cape Coral Bridge

28.35 (26.95)

28.98 (27.71)

Shell Point

34.50 (33.40)

35.22 (34.15)

 

Average salinities increased about 3 ppt in the upper estuary, and 1-2 ppt in the lower estuary.  Salinity at the Ft. Myers surface sensor was above the 1-day MFL criterion of 20 ppt.  The current surface salinity of 13.8 ppt at S-79 is 6.2 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

 

Recession rates in the conservation areas improved somewhat last week with low rainfall, high evapotranspiration and water management releases.  However, recession rates are highly variable across the region, best for wading birds in parts of WCA-1, 3A, and 3B.  WCA-2 recession rates are poor or fair   Most of the conservation area water depths remain well above the 1 foot maximum threshold for wading bird foraging. Stages in WCA-1 have declined but are still above Regulation Schedul, WCA-2A marsh remains more than 1’ above regulation, and WCA-3A stages continue to decline.

 

Everglades National Park

 

Very little rain fell across Everglades National Park (ENP) and Florida Bay last week again, producing another week of declining water levels across the ENP wetlands.

 

Salinity is rising across the Bay and mangrove transition zone, but concentrations are not abnormally high (i.e., this is typically the time of year when salinity concentrations can rise rapidly with conditions of no or low rainfall or incoming flow, and high evaporation). Near shore areas of Trout Creek, Taylor River mouth, and Little Madeira Bay are all reading near 30 psu.  Salinity in the Taylor ponds increased slightly for the week, into the upper 20s at Pond 5 and Argyle Hendry (station TR, used for Florida Bay MFL reporting); the 30 day moving average concentration at Taylor River increased slightly, up to 20 psu as of Sunday, 4/27 (up from 17.5 psu in last week’s report).  The central Bay salinity also increased this past week, into the mid-30s at Terrapin Bay and McCormick Creek, and into the upper 30s at Whipray Basin.  Except for the ponds, these concentrations are near their earlier concentrations before the rain events this month, and all areas (including the ponds) are well within seasonal norms.  Salinity remains high out west, downstream of Shark River Slough at Tarpon Bay (where salinity was back in the mid-teens as of Sunday, 4/27), but given the time of year is not too high (unlike earlier this dry season when this area experienced higher than average concentrations).

 

Water Supply

 

Last week was relatively dry, so most water levels decreased slightly across the District.  Water levels in the upper and lower Kissimmee Basin are now near their historical average conditions for this time of year.  Water levels in the Lower West Coast are a “mixed bag” of average to slightly higher than historical averages, depending on the degree of confinement of the aquifers.  Water levels in the Lower East Coast are near or slightly above their historical averages and wells recorded modest increases or decreases, depending on proximity to well-fields.  Water levels in the Upper East Coast remain well above their historic averages although they declined slightly this week.  Surface and groundwater levels in Water Conservation Areas 1 and 2 are now near or slightly above their historic averages.  Water levels in WCA 3A have rebounded to near their historic averages this week.  Water levels in the southernmost portion of Miami-Dade County are now above their average historic conditions.

 

Six out 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).

 

WSE (Lake Okeechobee Regulation Schedule)

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CC:   George Horne