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: October 14, 2008
SUBJECT: Weekly
Environmental Conditions for Systems Operations
Summary
Floodplain depths in the restored
area of the Kissimmee River continue to decrease and
On October 14th, the
United States Army Corps of Engineers (USACE) initiated baseflow
releases to both estuaries, with an overall average release of 450 cfs at S-79 to the
Background
Some fast moving showers south on
Tuesday, then it looks like the beginning of the Dry Season. The tail end of a trough across the District
is shifting southward and drier air is backing in from the northeast. Expect fast-moving scattered showers to
persist south of the trough especially near the east coast the remainder of
Tuesday. Breezy northeast winds will
keep some spotty showers east and south Wednesday and Thursday. A cold front is expected to move through the
District Saturday. Limited shower
activity is expected ahead of the front Friday and Saturday. Slightly cooler temperatures should spread
southward Saturday and Saturday night.
Breezy northeast winds should increase seasonally high tides through
Thursday. The next ten days
precipitation outlook is below average with low confidence.
Over the last seven days, the
upper
Discharge from
Wading bird surveys from last
Thursday revealed an estimate of 114 birds per square kilometer on the
floodplain. This estimate is nearly four
times higher than the performance measure target of 30 birds per square
kilometer. The actual number of birds
encountered may have been even greater if the flight had not been cut short due
to operations at
Despite decreases in flow and
stage within the restored reach of the river, water depths on the floodplain
currently range from 0.5 to 1.5 feet in general.
Observations made during a
fish shocking survey last week include the development of large sandbars due to
high flows from Tropical Storm Fay as well as numerous fish concentrated in
areas where water is flowing off of the floodplain into the river channel. From 10/7/08 to 10/14/08 dissolved oxygen
concentrations in the
According to the United
States Army Corps of Engineers (USACE) web site, Lake Okeechobee (
The monthly
submerged-aquatic-vegetation (SAV) survey was completed last week and 16 of the
35 sites sampled had plants. This was
the same as last month. Water clarity is
also similar to last month with an average secchi depth:total depth ratio of 0.36
(compared to 0.34 last month). Tannic
conditions remain in the north around King’s Bar and
in
September water-quality monitoring results are now available. All 25 monitoring stations had sufficient
water for sampling for the first time since January 2007. Total Phosphorus (P) averaged 128 ppb lakewide (compared to 98 ppb in August) and 118 ppb at nearshore stations (compared to 114 ppb in August). Total suspended solids (TSS) averaged 20 ppm lakewide (compared to 14 ppm in August) and 11 ppm
at nearshore stations (compared to 5 ppm in August).
September phytoplankton monitoring
results are also now available. Chlorophyll a concentrations averaged 19 ppb
across the nine monitoring sites and ranged between 4 ppb (Pahokee) and 31 ppb
(
Decaying terrestrial and
emergent vegetation may be depleting dissolved oxygen in areas of the littoral
zone with poor water circulation. For
example, low DO concentrations (<2 ppm)
were noted at three sites on the west side of King’s Bar last week. Algal blooms anticipated to appear in the
littoral zone in response to nutrient release from decaying vegetation have yet
to be reported.
St. Lucie Estuary
During the last week, an
average discharge of 893 cfs
occurred at S-80 from C-44 including 784 cfs at S-308
from the Lake, 236 cfs at S-97 from C-23, and 407 cfs from S-49 from C-24(discharge values from S-80, S-308,
S-97 are provisional). 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 |
|
0.46 (1.07) |
0.56
(1.86) |
|
HR1 (N. Fork) |
2.20 (5.65) |
4.79 (10.10) |
|
|
3.26 (7.14) |
3.83 (9.10) |
8.0 – 25.0 |
A1A Bridge |
10.85
(15.16) |
20.18 (21.99) |
20.0 – 31.0 |
Compared with the previous
week, average salinity decreased throughout the estuary. Salinities are close to the lower limit of
the preferred range at A1A Bridge, and below the preferred range at
Caloosahatchee Estuary
During the last week, an
average discharge of 3300 cfs occurred at S-79, 1121 cfs at S-78, and 649 cfs at S-77.
The concentration of chlorides at the
Olga Plant was 46 ppm on Monday, down from 59 ppm at the beginning of this reporting period. The current weekly average salinities (in
bold) at the six monitoring sites in the Caloosahatchee Estuary are given below
in parts per thousand (ppt), along with the previous
week’s (in parenthesis).
|
Weekly Average Salinity
(ppt) |
|
Sampling Site |
Surface |
Bottom |
|
0.24 (0.23)
|
0.25
(0.24) |
Rt. 31 Bridge |
0.24
(0.23) |
0.25
(0.24) |
I-75 Bridge |
0.26
(0.25) |
0.27
(0.26) |
|
0.29 (0.25)
|
0.30 (0.25) |
|
3.10 (1.00)
|
5.71(1.93) |
Shell Point |
16.61 (12.95)
|
20.12 (16.92) |
In the estuary, freshwater
conditions extend from S-79 downstream to
Compared with the previous
week, average salinity remained about the same in the upper estuary. An
increase in salinity for about 2-4 ppt occurred in
the lower estuary downstream of
Fish and Wildlife
Research Institute (FWRI) reports that low concentrations of Karenia brevis, the
Water Conservation Areas
Stage changes
were mixed this week. Stages declined
slightly in WCA-2B and WCA-3A (-0.05’ to -0.10’), with a larger drop in
Northeast Shark River Slough (-0.15’).
Stages rose in WCA-1 between 0.02’ to 0.18’, in WCA-2A by 0.07’, with a
local, large increase in WCA-3B (0.11’ to 1.15’). Average basin stage changes are listed below:
Change: WCA-1: 0.10 ft
WCA-3A: -0.04 ft
WCA-2A: 0.07 ft
WCA-3B: 0.48 ft
WCA-2B:
-0.06
ft NESRS:
-0.15 ft
Stages in WCA-1
are at regulation depths. WCA-2A stages
rose slightly again this week, and are still above their regulation stage, as
they have been for more than one full year.
The stage in WCA-3A declined slightly again this week (-0.04 foot) but
is still over a foot above regulation, continuing an exceedance
that began in mid-July.
Water depths at
two gauges in the Greater Everglades (GE) continue to exceed 4 feet: 4.06 feet in the southern portion of WCA-2B
and 4.05 feet in southern WCA-3A. These
depths are typical for this time of year, but deeper than desired for local
tree islands. The lowest depth this week
in the GE is 1.69 feet in northern Everglades National Park (ENP). All gauges in WCA’s
2B and 3A exceed 2.5 feet, a generalized threshold for tree island
inundation. Continuous inundation beyond
120 days potentially threatens the health of trees on the tree islands, so
sequential Inundation Days are now being tracked. The ponded region
of WCA-2B is now 91 days above this threshold of 2.5 feet, southern WCA-3A is
77 days above it, and northern and central areas of WCA-2B and -3A are 42-63
days into this 120 day period.
Rainfall was
patchy last week across Everglades National Park (ENP) and
Stage changes in
ENP wetland areas were mixed. After last
week's significant increases, water levels rose by only 0.25 inches at
Salinity dropped
or remained stable across
Water Supply
Water levels in the upper and
lower
Water levels in the Lower
West Coast are mostly above their historical averages although wells in the
upper
Ten out of the eleven water
supply risk indicator parameters are now in the “low” risk category, including
the CPC Precipitation Outlook, Palmer Index for Tributary Conditions, the Lake
Okeechobee Seasonal and Multi-seasonal Net Inflow Forecast, and Water Conservation
Areas 1, 2A and 3A. The projected Lake
Okeechobee Stage and LEC Service Areas 1, 2 and 3 (as a result of the removal
of water restrictions) are now in the “low” risk category.
The LOK Seasonal Net Inflow
Forecast has now turned from “low” to “medium” risk, on the anticipation of the
coming dry season.
LORS2008 (
Stages in Lake Okeechobee (
CC: George Horne