MEMORANDUM

 

 

TO:            Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:      SFWMD Staff Environmental Advisory Team

 

DATE:       April 22, 2008

 

SUBJECT: Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

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

 

Background

 

Limited light shower activity.  A surface low off the coast of South Carolina is expected to dig southward to off the coast of Jacksonville Wednesday.  Some moisture will wrap around its backside Wednesday and generate some spotty showers northeast Wednesday night.  As the low exits to the east, a reinforcing trough will pinwheel around the low and bring some scattered showers mainly north and east Thursday and then south and west Friday.  The next ten days precipitation outlook is below average with moderate confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received 0.03 inches of rainfall to bring the 30 day total to 3.75 inches (142% of average), and the lower basin received 0.01 inches to bring the 30 day total to 4.10 inches (170% of average).  In the upper basin, water levels are falling in most of the smaller lakes without having to make releases for the spring recession.  Releases are being made from East Lake Tohopekaliga (S-59) of 100 cfs, from Lake Tohopekaliga (S-61) of 400 cfs, and from Lake Kissimmee (S-65) of 1100 cfs.  No other releases are being made in the upper basin.

 

Hydrilla treatment continued in Lake Cypress last week.  For the first week of treatment, inflow from Lake Tohopekaliga and Lake Gentry was restricted.  Hydrilla treatment will continue. 

The vegetation removal project is continuing in Lake Gentry.  The Florida Fish and Wildlife Conservation Commission anticipates completing the project by the end of this week.  In the upper basin, snail kites continue to nest on East Lake Toho, Lake Toho, and Lake Kissimmee.  A whooping crane continues to nest on Lake Kissimmee.

 

The discharge from Lake Kissimmee (S-65) was decreased from 1500 cfs to 1100 cfs to slow the water level recession to more closely track the environmental recession line for snail kites and wading birds.  Flow has been reestablished to the Kissimmee River for 272 days (S-65 re-opened on 07/18/07).  The inflow from the upper basin continues to inundate a portion of the floodplain in the Phase I area of the Kissimmee River Restoration Project.  Dissolved oxygen concentrations in the river channel of the Kissimmee River ranged from 2.1 mg/L to 8.4 mg/L with an average of 3.9 mg/L, which is a slight increase over last week’s report.

 

Aerial surveys completed on April 10th found low numbers of wading birds within the restored section (ca. 13 birds/km2), while three large flocks of Glossy and White (mostly white) ibis were feeding in Pool D in isolated depressional wetlands that had been re-flooded after the prior week’s rain event, making the density in that pool ca. 61 birds/km2.  Ground surveys found over 1,500 migratory shorebirds (mostly Dowitchers, and Lesser and Greater yellowlegs) foraging over backfill and scraped areas in Phase IVa last week.

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 10.41’ NGVD, which is 0.07’ lower than a week ago and 0.25’ higher than a month ago.  The current stage is 0.50’ higher than it was a year ago and 3.50’ below its historical average for this time of year.  Total reported inflows of ~1500 cfs and includes the Kissimmee River (~1400 cfs) and the L8 at Canal Point (~100 cfs).  Outflows of 359 cfs are reported through the S77.

 

Field crews reported algal bloom conditions at several locations in the lake last week.  A surface bloom (possibly the toxin-producing Microcystis) was observed near the Pahokee Marina and evidence of bloom formation also was found at stations LZ40 (center of the lake), L005 (near the western shore), and L001 (near the northern shore).  Monthly phytoplankton monitoring is being conducted this week and samples will be collected for taxonomic analysis and toxin measurements.

 

St. Lucie Estuary

 

There were no releases through S-80 over the past week.  During this same period, discharge was minimal at S-49 from C-24 and at S-49 from the C-24, respectively averaging 1.64 cfs and 0.07 cfs.  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)

11.09 (10.13)

12.44 (10.41)

 

HR1 (N. Fork)

14.04 ( 9.19)

16.87 (13.40)

 

Roosevelt Bridge

15.93 (13.08)

18.02 (15.03)

8.0 – 25.0

A1A Bridge

24.66 (23.60)

27.79 (27.52)

20.0 – 31.0

 

Average salinity increased 1 to 2 ppt in the South Fork, 3 to 5 ppt in the North Fork, 3 ppt at Roosevelt Bridge, and 1 ppt on the surface at 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 16.0 ppt at the Roosevelt Bridge is 12 ppt below the maximum weekly average of 28.0 ppt achieved in May 2001 during the 2000 – 2001 drought.

 

Caloosahatchee Estuary

 

The direction of flow though S-77 at the beginning of the week was 166 cfs into Lake Okeechobee.  However, the net flow for the week from S-77 was 100 cfs into the eastern C-43 basin.  The S-78 gates were closed and there was no discharge through S-79 during the past week.  The concentration of chlorides at the Olga Plant yesterday was 186 mg/l, up from 155 mg/l 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)

11.06 (9.03)

11.73 (9.60)

Rt. 31 Bridge

10.89 (9.39)

NA (9.58)

I-75 Bridge

NA ( NA)

15.01 (16.04)

Ft. Myers Yacht Basin

19.40 (19.95)

20.41 (21.16)

Cape Coral Bridge

26.95 (26.87)

27.71 (27.74)

Shell Point

33.40 (33.44)

34.15 (34.25)

 

Average salinities increased 1 to 2 ppt in the upper estuary and remained the same in the lower estuary.  Salinity at the Ft. Myers surface sensor was again just below the 1-day MFL criterion of 20 ppt.  The current surface salinity of 11 ppt at S-79 is 9 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 near or 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 seagrass.

 

Water Conservation Areas

 

Low rainfall, high evapotranspiration and water management releases resulted in generally fair or good recession rates in WCA-1, WCA 2-A and WCA 3-A, but depths in most areas remain well above the 1 foot maximum threshold for wading bird foraging.  Stages in WCA-1 have declined and are now very close to Regulation Schedule, WCA-2A marsh remains well above regulation, and WCA-3A stages have declined and closely tracked regulation schedule.

 

Everglades National Park

 

In contrast to recent weeks, Everglades National Park (ENP) and Florida Bay saw very little rainfall last week.  In ENP, water level declined by 4.3” over the 7 day period at Taylor Slough Bridge (not an unusual recession rate at this station).  The southern part of Taylor Slough (at Craighead Pond) & northern areas of Shark River Slough (station P33) both saw weekly recession of 1.3”. Reliable water level readings for the panhandle station at EVER6 were unavailable this, but at EPSW (west of EVER6) stage was down by 1.2” for the week.

 

Salinity in Florida Bay increased last week.  Salinity rose above 30 psu again at Trout Creek and remained in the upper-20s at the mouth of L. Madeira Bay.  In the Taylor ponds, salinity rose into the lower mid-20s by the weekend at Pond 5 (USGS station) and Argyle Hendry (ENP station TR).  As of Sunday, 4/20, the 30 day moving average concentration at TR (used for tracking the FL Bay MFL criterion) was at 17.5 psu (up from 16.7 psu last week, and while not unseasonably high, the highest concentration we have seen yet this dry season).  Salinity also increased in the north central Bay areas of McCormick Ck. & Terrapin Bay, where concentrations once again rose into the mid-30s by the week’s end.  At the central Bay station in Whipray Basin salinity increased slowly through the week, into the upper-30s.  These salinity concentrations across FL Bay are near seasonal norms.  The most notable change in salinity occurred in the upstream reaches of Shark River (Tarpon Bay platform), an area where salinity has remained very high for much of the dry season: the daily mean measurement here dropped again this week (probably in response to recent rain events), down into single digit concentrations (~ 9 psu) as of Sunday, 4/20, near its seasonal norm.  It has been greater then 3 months since salinity was this low in this part of the system.


Water Supply

 

Last week was relatively dry, most water levels decreased slightly across the South Florida Water Management 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.  Surface and groundwater levels in Water Conservation Areas 1 and 2 are now above their historic averages as a result of local rainfall.  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.

 

Five out the eleven water supply risk indicator parameters are now in the “low” risk category, including the Lake Okeechobee Seasonal and Multi-seasonal Net Inflow Forecast, and Water Conservation Areas 1, 2A.

 

Five out the eleven water supply risk indicators are now in the “medium” risk category, including the Palmer Index for Tributary Conditions (dry) and the CPC Precipitation Outlook (normal to below normal) 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