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