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
28, 2008
SUBJECT: Weekly
Environmental Conditions for Systems Operations
Summary
Water depths on the restored
On October 14th, the
United States Army Corps of Engineers (USACE) initiated baseflow
releases to both estuaries, targeting an overall average release of 450 cfs at
S-79 to the
Background
Dry
and quite cool through Wednesday. Much
cooler air is arriving behind the passage of a secondary cold front. Look for unseasonably cool temperatures with
some record lows likely Wednesday morning over many sections of the
District. Then, deep layered high
pressure will dominate with warmer temperatures arriving by Thursday along with
some minor showers east by Friday. Next
chance for significant rainfall appears at least 10 days away.
Over the last seven days, the
upper Kissimmee Basin received 0.66 inches of rainfall to bring the 30 day
total to 3.98 inches (124% of average) and the lower basin received
approximately 0.60 inches to bring the 30 day total to 3.92 inches (127% of
average).
Water levels in most of the
upper basin lakes continue to closely follow their regulation schedules. Stages in Lakes Kissimmee, Hatchineha
and
Discharge from
Water depths on the
floodplain currently range from 0.5 to 1.4 feet in general.
Large numbers of wading birds
are foraging on the floodplain.
From 10/21/08 to 10/28/08
dissolved oxygen (DO) concentrations in the
According to the Unites
States Army Corp of Engineers (USACE) web site,
Last week, field crews resampled 59 annual mapping grid cells that had submerged
aquatic vegetation (SAV) in August prior to Tropical Storm Fay. Plants were still present at 32 of the cells
(compared to 37 cells in September) and 13 of the cells were too deep to sample
(the same as in September). The average secchi depth:total
depth ratio was 0.35 (compared to 0.37 in September).
A survey was conducted last
week to determine the status of large numbers of the endangered Okeechobee
Gourd that became established on the southern islands during the drought. Recent water level rises
flooded and killed established plants, which typically senesce at this time of
year anyway. Large numbers of fruits
(gourds) were located and the vegetation management group will be requesting a
permit to transport these propagules to more suitable
locations.
St. Lucie Estuary
Over the past week, discharge
averaged 212 cfs at the S-80. Discharge from the
|
Weekly Average Salinity
(ppt) |
|
|
Sampling Site |
Surface |
Bottom |
Envelope |
|
2.96 (0.77) |
3.71(0.83) |
|
HR1 ( |
4.81 (1.66) |
9.49 (4.30) |
|
|
8.30 (4.41) |
10.87 (5.52) |
8.0 – 25.0 |
A1A Bridge |
19.62 (16.32) |
25.78 (23.90) |
20.0 – 31.0 |
Compared with the previous
week, average salinity increased from 2.2 ppt to 5.3 ppt throughout the
estuary. Bottom salinity at the A1A
Bridge is within the preferred range and the surface salinity is close to the
lower limit of the preferred range at the A1A Bridge. Salinity at
Caloosahatchee Estuary
During the last week,
discharge averaged 849 cfs at the S-79, 275 cfs at the S-78, and 0 cfs at the S-77.
The concentration of chlorides at the
Olga Plant was 55 ppm yesterday. 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 |
|
0.29 (0.26) |
0.55 (0.27) |
Route 31 Bridge |
0.52 (0.27) |
NR (0.28) |
I-75 Bridge |
0.82 (0.31) |
1.99 (0.36) |
|
4.46 (1.19) |
7.32 (2.93) |
|
11.53 (6.78) |
14.71 (10.03) |
Shell Point |
24.73 (21.36) |
NR (22.48) |
Salinity conditions in the
upper estuary east of
An increase in salinity 3-5 ppt
occurred downstream of
Fish and Wildlife
Research Institute (FWRI) reports that background concentrations
of Karenia brevis,
the
Water Conservation
Areas
Rain was
relatively heavy in the central regions of the Everglades Protection Area (EPA),
especially in WCA-2B. Pan evaporation of
1.18 inches was essentially the same as the rainfall, producing no net change
in system volume. Basin-level rainfall
values for the week ending on 10-27-08 were:
RAIN: WCA-1: 0.97 inches WCA-3A: 1.25
inches
WCA-2A: 1.59
inches WCA-3B: 0.69 inches
WCA-2B: 3.30 inches ENP: 1.26
inches
Stage changes
were essentially unchanged from last week, except for WCA-2B, where a high
rainfall cell deposited 3.3 inches of rain. Average basin stage changes for the week
ending on 10-27-08 were:
Stage Change: WCA-1: 0.04 foot WCA-3A: -0.04
foot
WCA-2A: 0.08 foot WCA-3B: 0.02
foot
WCA-2B: 0.32 foot NESRS: 0.06
foot
Stage change
compared to one month ago, throughout the Greater Everglades indicate that
WCA-2A and WCA-3A have been getting slightly shallower, while the rest of the
system has been getting slightly deeper. The EPA is at a seasonal high in terms of
depths. The southern region of WCA-3A
has 3.82 feet of water and is now 91 days above the tree island threshold of
2.5 feet. The northern region of WCA-3A,
on-the-other-hand, has only 2.33 feet of water and is no longer above the tree
island threshold. Other high depth
regions include: WCA-1, 2A, 2B, central 3A, and northern 3B. So far, none of these regions have exceeded
the 120 day maximum duration for tree islands.
With the end of
the rainy season, stages are expected to drop gradually to 2.5 feet or below,
except in southern WCA-3A, before tree islands are expected to experience flooding
stress.
Stages in WCA-1
are slightly below regulation depths. WCA-2A
stages are declining but are still above their regulation stage, as they have
been for more than one full year. The
stage in WCA-3A has stabilized at last week’s level and remains over a foot
above regulation, continuing an exceedance that began
in mid-July.
Stages in Everglades National
Park (ENP) were up slightly or unchanged last week. Water levels in Shark River Slough, Craighead
Pond, and the ENP panhandle were up by approx. 0.5 inches over the 7-day
period.
Salinity increased slightly
or remained stable across
Water Supply
Water levels declined
slightly across most of the District this week, as a result of relatively light
rainfall. Water levels in the upper and
lower Kissimmee Basin (KB) are now near their average conditions for their
respective periods of record. Groundwater
levels in the western portion of the upper KB are generally lower than those in
the eastern portion. Water levels in the
Lower West Coast are mostly well 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 Lower East Coast (LEC) Service Areas 1, 2
and 3 (as a result of the removal of water restrictions) are now in the “low”
risk category. The Lake Okeechobee
Seasonal Net Inflow Forecast has turned from “low” to “medium” risk, on the anticipation
of the coming dry season.
LORS2008 (
Stages in
CC: George Horne