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 Lake Okeechobee levels have stabilized.  Lake vegetation continues to show signs of stress, and the lower estuaries are still experiencing undesirable low salinities. Water levels are at or above schedule in all of the Water Conservation Areas.  

 

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 Caloosahatchee River and 200 cfs at S-80 to the St, Lucie River. 

 

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.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received approximately 2.28 inches of rainfall and the lower basin received approximately 2.07 inches.  Water levels in the upper basin lakes continue to closely follow their regulation schedules.  Stage in Lakes Kissimmee, Hatchineha and Cypress, has increased slightly and is now 0.4 foot below regulation schedule.

Discharge from Lake Kissimmee remained at approximately 300 cfs and discharge at S65C increased slightly from 350 cfs to 468 cfs.

 

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 Avon Park Bombing Range.  A flock of 12 roseate spoonbills was also observed using the floodplain.  This is largest number of spoonbills that have been observed in this area to date.

 

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 Kissimmee River ranged from 0.62 mg/L to 6.29 mg/L and averaged 3.41 mg/L.

 

Lake Okeechobee

 

According to the United States Army Corps of Engineers (USACE) web site, Lake Okeechobee (Lake) stage is 14.99’ NGVD, which is 0.03 foot higher than a week ago, 0.15 foot lower than a month ago, and 4.89 feet higher than it was a year ago.  The current stage is 0.05 foot below the historical average for this date, and 1.03 feet above the simulated historical average for the current regulation schedule (LORS2008).  Total reported inflows are 2727 cfs, with the greatest contributions from S71 and S72 (1692 cfs), the Kissimmee River (652 cfs), and S191 (208 cfs).  No daily flow data are available for the S77 and S308 structures, but real-time data indicate that small outflows continue through these structures.

 

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 Fisheating Bay.  Water depths at many of the lakeward sites are greater than 2 meters, and SAV beds in these areas may begin to show signs of stress in the coming months if these conditions persist.  The coverage of Chara is declining at the south end of the Lake and has disappeared from Pelican Bay.

 

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 (Observation Island).  Microcystin levels were at or below the 0.2 ppb detection limit at all sites except for Harney Pond (0.3 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

Palm City Bridge (S. Fork)

0.46 (1.07)

0.56 (1.86)

 

HR1 (N. Fork)

2.20 (5.65)

4.79 (10.10)

 

Roosevelt Bridge

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 Roosevelt Bridge.  Salinity conditions in the estuary are still considered to be poor based on the salinity preference of the oyster, Crassostrea virginica, and location in the estuary.

 

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

Franklin Locks (S-79)

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)

Ft. Myers Yacht Basin

0.29 (0.25)

0.30 (0.25)

Cape Coral Bridge

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 Cape Coral Bridge.  Salinity conditions in the upper estuary east of Fort Myers are good (30 day average at Fort. Myers equals 0.31 ppt).

 

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 Cape Coral Bridge.  However, salinities at Cape Coral Bridge and Shell Point are still below the preferred ranges for both oyster, Crassostrea virginica, and seagrass, Halodule wrightii.  Therefore, conditions in the lower estuary are considered poor.

 

Fish and Wildlife Research Institute (FWRI) reports that low concentrations of Karenia brevis, the Florida red tide organism, were detected this week in water samples collected along Captiva Island (Lee County).  No impacts have been reported.  All other water samples collected alongshore from Pinellas and Charlotte counties contained no K. brevis.  A research cruise, currently being conducted, found medium concentrations of K. brevis in Lee County off and alongshore of Cayo Costa State Park.  Monitoring data collected by the River, Estuary and Coastal Observing Network (RECON) of Sanibel-Captiva Conservation Foundation (SCCF) indicated that Chlorophyll concentrations over the last week were about 4.5-5.5 ug/L at Fort Myers and 1.5 to 4 ug/L at Shell Point.  The DO concentration at the two locations ranged from about 4 to 6 mg/L.

 

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.   Central WCA-2A is still below this threshold.

 

Everglades National Park

 

Rainfall was patchy last week across Everglades National Park (ENP) and Florida Bay.  ENP stations reported between 0.1 inch and 3.0 inches of cumulative rainfall with highest accumulations in the eastern part of the system.  The basin-wide spatially-averaged weekly totals were 1.07 inches and 1.66 inches in the ENP and C-111 basins, respectively).

 

Stage changes in ENP wetland areas were mixed.  After last week's significant increases, water levels rose by only 0.25 inches at Taylor Slough Bridge and by 0.6 inch in the ENP panhandle at EVER6.  Stages declined -0.5 inch in Shark River Slough (P33) and -2 inches in southern Taylor Slough at Craighead Pond.  Overall, wetland stages across much of ENP remain well above their seasonal normal averages.

 

Salinity dropped or remained stable across Florida Bay.  Salinity readings from the creeks feeding eastern Florida Bay remained below 10 psu until the latter part of the week, when concentrations increased into the teens.  The 30 day moving average salinity at the Taylor River platform declined from 8.7 psu last week to 6.5 psu on Sunday.  In the north central Bay, salinity remained in the low 20s in Terrapin Bay and McCormick Creek.  The Whipray Basin salinity remained near 35 psu throughout the week.  Salinity remained near seasonal norms in upstream reaches of Shark River (Tarpon Bay platform, where salinity is below 1 psu).

 

Water Supply

 

Water levels in the upper and lower Kissimmee Basin are now near or slightly above their average conditions for their respective periods of record, reflecting generally wet conditions north of Lake Okeechobee this week.  Groundwater levels in the western portion of the upper Kissimmee Basin are generally still lower than those in the eastern portion.


Water levels in the Lower West Coast are mostly above their historical averages although wells in the upper Caloosahatchee River Basin continue to be below their historic conditions.  Water levels in the Lower East Coast are now above their historical averages; they experienced continued recovery this week as a result of local rainfall.  Water levels in the Upper East Coast remain above their historic averages and are close to their highest recorded values.  Surface and groundwater levels in Water Conservation Areas 1, 2 and 3 continue to remain above their historic averages this week; the highest recorded levels were within Water Conservation Areas 1 and 2.

 

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 (Lake Okeechobee Regulation Schedule)

 

Stages in Lake Okeechobee (Lake) are now within the low sub-band.  Inflows from the tributary basins have continued to taper off and are currently in the normal category for the tributary hydrologic conditions.  The seasonal outlook for net inflow into the lake is for dry conditions.  The LORSS recommended discharges are up to 450 cfs at S-79 and up to 200 cfs at S-80, and maximum practical discharges to the south if desired or with minimal impact.

 

 

 

 

 

 

 

 

CC:      George Horne