MEMORANDUM

 

 

TO:            Chip Merriam, Deputy Executive Director, Water Resources

 

FROM:      SFWMD Staff Environmental Advisory Team

 

DATE:       March 11, 2008

 

SUBJECT: Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

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

 

Background

 

Some showers and thunderstorms today and Friday.  An old frontal boundary is pulling north into south Florida and some upper level energy in the central Gulf of Mexico will move across the area today and tonight.  Expect patches of rain with embedded showers and thunderstorms to move across mainly the southern half of the District today and tonight.  Drier conditions should then settle over the District Wednesday and Thursday.  A second energy impulse moving across the area should bring another round of showers and thunderstorms focused over central Florida Friday.  The next ten days precipitation outlook is below average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received approximately 2.52 inches of rainfall to raise the 30-day total to 3.74 inches (130% of average) and the lower basin received 2.48 inches to raise the 30-day total to 4.50 inches (180% of average.  Water levels in the upper basin lakes are at or below their regulation schedules.

 

The discharge from Lake Kissimmee (S-65) has been increased to approximately 900 cfs to the Kissimmee River to avoid an increase in lake stage during the nesting season.  Releases of 1200 cfs are being made from Lake Toho (S-61) and of 600 cfs from East Lake Toho to allow a more gradual water level recession during the snail kite nesting season.  Last week releases began from Lakes Hart and Mary Jane and from Lakes Myrtle, Preston and Joel because rainfall was causing water levels to rise to the regulation schedule.  No other releases are being made in the upper basin.

 

In the upper basin, snail kites continue to nest on East Lake Toho and Lake Toho.  A whooping crane continues to nest on Lake Kissimmee.

 

Flow has been reestablished to the Kissimmee River for 230 days (S-65 re-opened on 07/18/07).  Dissolved oxygen concentrations in the river channel of the Kissimmee River ranged from 5.33 mg/L to 8.06 mg/L with an average of 7.0 mg/L.

 

A recommendation was made last week to hold the water level in Lake Kissimmee at the current elevation to avoid an increase (reversal), which could impact on nesting by the endangered snail kite and on the reproduction of their primary food source the Florida apple snail.  Last week’s recommendation was followed up this morning with a recommendation to begin lowering the water level of Lake Kissimmee to the same low stage of 49 ft by June 1 as the regulation schedule.  Starting the recession earlier will lower the water levels more gradually, which should benefit the reproduction of snail kites and apple snails.

 

Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 10.13’ NGVD, which is 0.06’ higher than a week ago and 0.12’ higher than a month ago.  The current stage is 0.89’ lower than it was a year ago and 4.43’ below its historical average for this time of year.  Reported inflows cfs include the Kissimmee River (~400 cfs), the S71 and S72 structures (~425 cfs), and the L8 at Canal Point (~650 cfs).  No outflows are reported.

 

The monthly submerged-aquatic-vegetation (SAV) survey was completed last week.  Water clarity increased slightly with secchi depths greater than 50% of total depths at 23 of the 28 sites sampled compared to 19 of 29 sites sampled in February.  The macroalga Chara remains the dominant SAV species and was found at 10 of the 28 sites sampled.  One species of vascular SAV, Vallisneria americana, continues to be present in very low density at a few sites around King’s Bar on the northern shoreline and a few sites along the western shoreline.

 

Results of the February phytoplankton bloom monitoring are now available.  Six of nine sites had sufficient water to access for sampling.  Chlorophyll a values averaged 11.2 ppb and algal toxin (microcystin) levels were below detection (0.2 ppb) at all sites.

 

Sediment cores were collected from locations in Fisheating Bay where the newly discovered and potentially invasive exotic water grass Luziola subintegra is growing.  These cores will be incubated in the laboratory under different hydrologic conditions to monitor seed germination and assess whether a viable seed bank of this species has been established in the lake.

 

St. Lucie Estuary

 

There were no releases through S-80 over the past week.  Discharge at S-97 on the C-23 Canal averaged 25.79 cfs and S-49 on the C-24 canal 0.06 cfs 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)

10.30 (13.11)

11.71 (14.36)

 

HR1 (N. Fork)

15.58 (16.85)

16.76 (18.51)

 

Roosevelt Bridge

18.42 (20.35)

18.62 (20.78)

8.0 – 25.0

A1A Bridge

26.30 (27.86)

28.11 (29.23)

20.0 – 31.0

 

Average salinity decreased 1 to 3 ppt throughout the estuary due to local rainfall.  Both the surface and bottom salinity are in the preferred range at the Roosevelt Bridge, and at the A1A Bridge.  Based on the salinity tolerances of the oyster, Crassostrea virginica, salinity conditions in the estuary are good.  The current surface salinity of 18.42 ppt at the Roosevelt Bridge is 9.58 ppt below the maximum weekly average of 28.0 ppt achieved in May 2001 during the 2000 – 2001 drought.

 

Caloosahatchee Estuary

 

Discharge at S-79 over the past week averaged 58.57, an increase from the previous week with no releases.  The 30-day average is 61 cfs.  Freshwater flow back into the Lake from C-43, through S-77, averaged 18.86 cfs during the last week.  The concentration of chlorides at the Olga Plant were stable during the last week , with 228 mg/l reported yesterday.  Average salinity increased by 1 to 2 ppt throughout the estuary. 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)

16.68 (14.46)

16.64 (15.26)

Rt. 31 Bridge

16.86 (14.36)

17.73 (16.81 )

I-75 Bridge

NA (NA)

19.86 (17.78)

Ft. Myers Yacht Basin

23.11 (21.97)

23.15 (22.37)

Cape Coral Bridge

30.53 (27.46)

31.07 (30.21)

Shell Point

34.86 (34.15)

36.22 (35.34)

 

Salinity at the Ft. Myers surface sensor remains above the 1-day MFL maximum criterion of 20 ppt.  The current surface salinity of 16.68 ppt at S-79 is 3.32 ppt below the maximum weekly average of 20.0 ppt achieved in May 2001 during the 2000 – 2001 drought.  Salinity at the Cape Coral Bridge is above the upper limit of the optimal range for the oyster, Crassostrea virginica.  However, salinity for seagrass in the area downstream of Cape Coral sensor is good.

 

In summary, conditions in the upper estuary east of Ft. Myers are poor due to high salinity.  Based on the tolerances of oysters, salinity conditions downstream of Cape Coral are poor.

 

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

 

Water depths increased almost everywhere creating significant reversal (as much as 0.25 ft at gauge 62), as a result recession rates were designated as poor.  At the same time, water depths remain above one foot and above the optimum depths for wading bird foraging. It is still early in the nesting season and it is hoped that these poor hydrologic conditions will have a minimum impact.  Stages in WCA-1 are now above Regulation, WCA-2A marsh remains above regulation (note: canal levels dropped sharply due the opening of the S-11’s), and WCA-3 stages are now only slightly below the E1 regulation schedule

 

Everglades National Park

 

Water levels across Everglades National Park (ENP) wetlands continued to decline.   Stage was down by 0.6” in Shark River Sl. (station P33) last week.  At Taylor Slough bridge water level dropped by just over 3” in the past 7 days (not an uncharacteristic decline for this area).  To the south, water level declined by 0.8” in Craighead Pond and by 1.1” in the ENP panhandle (station EVER6).

 

Salinity concentrations remained generally stable or increased slightly in Florida Bay last week. As a whole regional salinity concentrations are near seasonal norms.  Salinity concentrations in the Taylor ponds remained in the low single digits for much of last week.  The 30-day moving average concentration at Argyle Hendry was 5.5 psu and is not in violation of MFL’s.  The most substantial change in salinity last week occurred in the north-central Bay areas of McCormick Creek and Terrapin Bay where concentrations jumped from the teens into the mid-20s (McCormick Creek) and even 30 psu (Terrapin Bay); due to strong winds pushing Bay water northward.  The exception to near-normal trend was out west, in areas downstream of Shark River Slough where salinity rose to 20 psu in Tarpon Bay, a concentration that is above normal for even the latest parts of the dry season (May).


Water Supply

 

Water levels in the upper and lower Kissimmee Basin and remain slightly below their historical average conditions for this time of year – although they increased somewhat this past week as a result of local rains.  Water levels in the Lower West Coast are a “mixed bag” of slightly higher and lower 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 most wells recorded modest increases in water levels this past week.  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 near their average historic conditions.

 

There was modest improvement in the Water Supply Risk indicators this week.  Five out of eleven risk measures are in the “high” risk category including the projected Lake Okeechobee Stage (SSM), the CPC Precipitation Outlook, and Lower East Coast Service Areas 1, 2 and 3.  The Palmer Index for LOK Tributary Conditions improved from “high” to “moderate” risk this week.

 

The LOK Seasonal Net Inflow and the LOK Multi-Seasonal Net Inflow Forecasts remain at “medium” risk this week.  Water Conservation Areas 1, 2A and 3A continue to be in the “low” risk category.

 

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