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 21, 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 (Lake) 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

 

Potential for heavy rains on Thursday and Friday.  A weak post-frontal trough is across central Florida and it will generate a few light showers mainly east as it lifts back north.  A weak low over the northwestern Caribbean is forecast to move northward across Florida on Friday.  Expect showers to increase south Wednesday as this low begins to lift the old frontal boundary back north.  Shower activity will then increase further Thursday as the boundary lifts to near Lake Okeechobee by Friday morning followed by widespread moderate to heavy rains Friday as the low moves across the area.  The exiting low is then expected to bring the front back south through the district Saturday with scattered showers and thunderstorms followed by cool and dry conditions Sunday  The next ten days precipitation outlook is near average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received 0.34 inches of rainfall to bring the 30 day total to 3.93 inches (98% of average) and the lower basin received approximately 0.16 inches to bring the 30 day total to 4.2 inches (108% of average).

 

Water levels in the upper basin lakes continue to closely follow their regulation schedules.  The stage in Lakes Kissimmee, Hatchineha and Cypress is now 0.6 foot below regulation schedule. 

Discharge from Lake Kissimmee remained at approximately 300 cfs and discharge at S65C remained at approximately 450 cfs.  Water depths on the floodplain currently range from 0.5 to 1.5 feet in general.

Large numbers of wading birds are foraging on the floodplain.

 

From 10/14/08 to 10/21/08 dissolved oxygen (DO) concentrations in the Kissimmee River ranged from 2.4 mg/L to 6.8 mg/L and averaged 4.7 mg/L.


Lake Okeechobee

 

According to the Unites States Army Corp of Engineers (USACE) web site, Lake Okeechobee stage is 14.91’ NGVD, which is 0.08 foot lower than a week ago, 0.18 foot lower than a month ago, and 4.75 feet higher than it was a year ago.  The current stage is 0.15 feet below the historical average for this date, and 0.90 foot above the simulated historical average for the current regulation schedule (LORS2008).  Total reported inflows are 1253 cfs, with the greatest contributions from S84 (666 cfs) and the Kissimmee River (253 cfs).  Total reported outflows are 555 cfs and include 388 cfs through the S308 and 167 cfs to the L8 at Canal Point.

 

Monthly submerged aquatic vegetation (SAV) sampling was conducted along the southern shoreline last week.  A continued decline in Chara was reported, with sparse growth reported at 1 of 7 sites.  Water clarity remains poor, with secchi depths < 0.5 m and secchi depth:total depth ratios < 0.2.

 

Vegetation management crews are on the Lake treating large areas of exotic vegetation, including water hyacinth, West Indian marsh grass, and South American water grass (Luziola).  Treatment areas include Fisheating Bay, the northwest marsh, and the southern islands.  As many as 6 to 10 spray boats are expected to be active.  A crew is also treating Brazilian Pepper on Kreamer Island.

 

A survey will be conducted this week to determine the status of large numbers of the endangered Okeechobee Gourd that became established on the southern islands during the drought.

 

St. Lucie Estuary

 

During the last week, an average discharge of 210 cfs occurred at S-80 from C-44 including 185 cfs at S-308 from the Lake, 188 cfs at S-97 from C-23, and 207 cfs from S-49 from C-24(discharge values from S-97 and S49 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)

0.77 (0.46)

0.83 (0.56)

 

HR1 (N. Fork)

1.66 (2.20)

4.30 (4.79)

 

Roosevelt Bridge

4.41 (3.26)

5.52 (3.83)

8.0 – 25.0

A1A Bridge

16.32 (10.85)

23.90 (20.18)

20.0 – 31.0

 

Compared with the previous week, average salinity increased from < 1 ppt in North Fork and South Fork to about 4.5 ppt at A1A Bridge in the estuary.  Bottom salinity at A1A Bridge is within the preferred range and the surface salinity is close to the lower limit of the preferred range at A1A Bridge.  Salinity at Roosevelt Bridge is below the preferred range.  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 915 cfs occurred at S-79, 197 cfs at S-78, and 43 cfs at S-77.  The concentration of chlorides at the Olga Plant was 53 ppm on Monday, up from 46 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)

0.26 (0.24)

0.27 (0.25)

Rt. 31 Bridge

0.27 (0.24)

0.28 (0.25)

I-75 Bridge

0.31 (0.26)

0.36 (0.27)

Ft. Myers Yacht Basin

1.19 (0.29)

2.93 (0.30)

Cape Coral Bridge

6.78 (3.10)

10.03 (5.71)

Shell Point

21.36 (16.61)

22.48 (20.12)

 

In the estuary, freshwater conditions extend from S-79 downstream to Fort Myers Yacht Basin.  Salinity conditions in the upper estuary east of Ft. Myers are good (30 day average at Fort Myers equal 0.48 ppt).

 

Compared with the previous week, average salinity remained about the same in the upper estuary to I-75.  An increase in salinity of 1-2.5 ppt occurred at Fort Myers Yacht Basin and 3- 5 ppt in the lower estuary downstream of Cape Coral Bridge.  Salinities at Cape Coral Bridge are still below the preferred ranges for both oyster, Crassostrea virginica, and seagrass, Halodule wrightii.  Therefore, conditions in the lower estuary are still considered poor in spite of the improvement occurring over the last week.

 

Fish and Wildlife Research Institute (FWRI) reports that background concentrations of Karenia brevis, the Florida red tide organism, were detected this week in water samples collected at the Gasparilla Fishing Pier (Charlotte County), South Seas Plantation (Captiva, Lee County) and Lovers Key State Park (Lee County).  All other water samples collected alongshore between Pinellas and Collier counties contained no K. brevis.  A bloom of K. brevis, identified last week west of Lee County, remains slightly offshore (0.5 to 4 miles) between Cayo Costa and Captiva islands.  No impacts have been reported.  Monitoring data collected by the River, Estuary and Coastal Observing Network (RECON) of Sanibel-Captiva Conservation Foundation (SCCF) indicated that over the last week Chlorophyll concentrations were about 3.5-4.5 µg/L at Fort Myers and 1.5-3.5 µg/L at Shell Point.  The DO concentration at the two locations ranged from about 5-7 mg/L.

 

Water Conservation Areas

 

Stage changes declined throughout the Greater Everglades (GE).  The greatest drop in stage occurred in WCA-2A (-0.32’) and the least in WCA-1 (-0.05’).  Average basin stage changes are listed below:

 

Change:          WCA-1:           -0.05 ft             WCA-3A:         -0.20 ft

WCA-2A:         -0.32 ft             WCA-3B:         -0.10 ft

WCA-2B:         -0.16 ft             NESRS:          -0.19 ft

 

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.  With the end of the rainy season, we expect stages to drop gradually as evapotranspiration exceeds rainfall.

 

Water depths in the Greater Everglades are now below 4 feet at all gauges, and depths at two gauges (EDEN-13 in WCA-2B and Site 62 in WCA-3A) have dropped below 2.5 fee, the general threshold for tree islands.  Parts of WCA-1, -2, -3A, and 3B are still above this threshold.  So far none of these regions have exceeded the 120 day maximum duration for tree islands.  The two gauges with the longest inundation periods are the ponded region of WCA-2B at 98 days and southern WCA-3A at 84 days.

 

Everglades National Park

 

Light to moderate rainfall accumulations were measured last week (from Sunday to Sunday) across Everglades National Park (ENP) and Florida Bay.  Stations for which we receive data from ENP reported between 0.1 inch – 1.2 inches of rainfall for this seven day period.  The basin-wide spatially-averaged weekly RAINDAR totals were 0.4 inch and 0.5 inch in the ENP and C-111 basins, respectively.

 

Stages in ENP wetland areas declined for the week.  Several areas, including Shark River Slough, Craighead Pond, and the ENP panhandle, dropped by approximately 1 inch over the seven day period.  Stages at Taylor Slough Bridge dropped approximately 2 inches for the week.  Wetland stages across much of ENP remain well above their seasonal averages except at Craighead Pond, where the water level is at its seasonal average.

 

Salinity dropped or remained stable across Florida Bay.  Salinity in the eastern Bay is near seasonal levels and should be approaching its annual minimum.  The 30 day moving average salinity at the Taylor River platform (used for tracking the Florida Bay MFL criterion) declined again last week, from 6.5 psu last week down to 5.6 psu as of Sunday, 10/19.  In the north central Bay, salinity remained in the low 20s in Terrapin Bay and fell below 20 psu just upstream in McCormick Creek.  The central Bay platform at Whipray Basin recorded another week of salinity remaining near 35 psu.  For a second month, salinity remained near seasonal concentrations in upstream reaches of Shark River (Tarpon Bay platform, where salinity is nearly fresh under 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 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 Caloosahatchee River Basin continue to be below their average 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 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 to normal 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