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:                 July 1, 2008

 

SUBJECT:         Weekly Environmental Recommendation for Systems Operations

 

Recommendation

 

No Lake Okeechobee regulatory releases to the south or estuaries are recommended.

 

Background

 

Numerous showers and storms today.  There are several favorable elements for thunderstorm development evident in this morning’s analysis.  Light steering winds make it somewhat problematic in determining a focus; however, there should be a tendency for afternoon through early evening activity to align from Collier County northeastward through St. Lucie County.  Upper level winds become a little less favorable on Wednesday while the east coast seabreeze makes a little more inland penetration.  This should result in some decrease in storm coverage with a focus west through north of the Lake tomorrow afternoon/evening.  Upper level winds begin to become more favorable again for storm development late Thursday and especially Friday, so look for activity to increase by Friday.  Longer term, there is some evidence the atmosphere will begin to transition to a more typical July pattern in about 7-10 days.  If so, overall rainfall would also decrease.  .  The next ten days precipitation outlook is average with low confidence.

 

Kissimmee Watershed

 

Over the last seven days, the upper Kissimmee Basin received 2.12 inches of rainfall to bring the 30 day total to 7.63 inches (105% of average), and the lower basin received 2.09 inches to bring the 30 day total to 7.37 inches (106% of average) (Daily Rainfall Report 6/30/08).

 

With the continued rainfall, water levels are rising in all of the lakes, except Lake Kissimmee.  All lakes remain below regulation schedule, but several are approaching their regulation schedule elevation for summer.   

 

In the upper basin, snail kites continue to nest on East Lake Toho, Lake Toho, and Lake Kissimmee.  

 

Flow has been reestablished to the Kissimmee River for 350 days (S-65 re-opened on 07/18/07).  Flow is approximately 200 cfs at S65.  River water levels within the Kissimmee River Restoration Project area have been rising and falling in response to rainfall events.

 

Dissolved oxygen concentrations in the river channel of the Kissimmee River are beginning to fall below thresholds of concern temporarily.  Concentrations ranged from 0.1 mg/L to 5.4 mg/L and averaged of 4.2 mg/L. 


Lake Okeechobee

 

According to the USACE web site, Lake Okeechobee stage is 9.65’ NGVD, which is 0.33’ higher than a week ago and 0.05’ higher than a month ago.  The current stage is 0.79’ higher than it was a year ago, 3.87’ below the historical average for this date, and 2.62’ below the simulated historical average for the current regulation schedule (LORS2008).  Total reported inflows are approximately 2314 cfs and include 352 cfs from the Kissimmee River, 1279 cfs through the S71, 94 cfs through the S84, and 589 cfs from the L8 at Canal Point.  No flows are reported for S308 and S77, and no outflows are reported.

 

The third monthly apple-snail egg survey was conducted along transects across the outer (flooded) edge of the littoral zone on June 25th.  Shallow water (<10 cm) limited the survey to the lakeward edge of the transects.  No apple snail eggs were found using this truncated survey method.  Previous research indicates that apple snails do not lay eggs in water this shallow.  Surveys during the previous two months recorded only 29 egg clusters along 3 adjacent transects near Indian Prairie Canal.  While additional remnant apple snail populations may be located as larger areas of the littoral zone reflood, findings to date indicate that they will be sparse and widely scattered.

 

St. Lucie Estuary

 

There were no releases through S-80 from C-44 over the past week.  An average discharge of 125.52 cfs through S-48 from C-23 and 90.32 cfs through S-49 from C-24 occurred 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).  The surface salinity at A1A Bridge is a three- day average.

 

 

Weekly Average Salinity (ppt)

 

Sampling Site

Surface

Bottom

Envelope

Palm City Bridge (S. Fork)

13.15 (17.42)

15.43 (19.76)

 

HR1 (N. Fork)

14.72 (17.66)

17.95 (22.02)

 

Roosevelt Bridge

18.30 (21.51)

19.15 (23.18)

8.0 – 25.0

A1A Bridge

24.68 (29.48)

NA (NA)

20.0 – 31.0

 

Compared with salinities of the previous week, average salinity decreased throughout the estuary due to local runoff.  Salinity declined between 3 ppt and 5 ppt depending on location and depth.  Salinity at Roosevelt Bridge and A1A Bridge are within the preferred range.  Salinity conditions in the estuary are considered good, based on the salinity preference of the oyster, Crassostrea virginica.  The current surface salinity of 18 ppt at the Roosevelt Bridge is 10 ppt below the maximum weekly average of 28.0 ppt achieved in May 2001 during the 2000 – 2001 drought.

 

Caloosahatchee Estuary

 

An average weekly discharge of 1039 cfs occurred at S-79.  The concentration of chlorides at the Olga Plant was 130 ppm yesterday, down from 228 ppm in the beginning of this reporting period.  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)

7.79 (13.53)

8.15 (14.80)

Rt. 31 Bridge

7.96 (16.8)

11.74 (20.10)

I-75 Bridge

10.08 (17.96)

15.71 (20.76)

Ft. Myers Yacht Basin

18.31 (23.75)

21.32 (24.16)

Cape Coral Bridge

26.68 (28.81)

26.99 (29.21)

Shell Point

33.03 (34.37)

33.30 (34.42)

 

Compared to last week, average salinities dropped between 3 ppt and 8 ppt depending on depth and location.  Average salinity at the Ft. Myers surface sensor was 18 ppt, which is 2 ppt below the 1-day MFL criterion of 20 ppt.  The current surface salinity of 8 ppt at S-79 is 12 ppt below the maximum weekly average of 20.0 ppt achieved in May 2001 during the 2000 – 2001 drought.  Salinity at Shell Point and the Cape Coral Bridge is within the optimal range for the oyster, Crassostrea virginica.  Salinity conditions in the upper estuary east of Ft. Myers have improved.  Conditions in the lower estuary downstream of Cape Coral are good considering the combine salinity preference of oysters and seagrasses.

 

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

 

Good recession rates occurred this past week in quite a few locations throughout the Everglades.  However, only two locations had both good recession rates and depths suitable for wading bird foraging (i.e., < 1.0 ft); one was the northern regions of WCA-1 and the other was WCA-3B.  Depths in WCA-2A continue to be below 1 ft however, reversals have been the trend in WCA-2A for the last three weeks.

 

Everglades National Park

 

Weekly rainfall accumulations across Everglades National Park (ENP) ranged from 0.1” – 3.7”, with higher totals picked up along the eastern Park boundary.  Spatially variable rainfall produced mixed trends for ENP wetland water levels.  Water level actually dropped in Shark River Slough (station P33) by 0.6” for the week.  This is in contrast to Taylor Slough Bridge, where water levels increased by nearly 11” (after a 16” increase last week), and are finally approaching average conditions for this time of year (near ground surface).  By comparison, stage increases were more modest in the panhandle (station EVER6, 7 d increase of 1.4”) and in the southern part of Taylor Slough at Craighead Pond (weekly increase of 2”).  Moderate flows (< 200 cfs) from S332D continue to be delivered towards Taylor Slough, while higher flows (300 - 1000 cfs) have been recorded through the S18C panhandle spillway since 6/19.

 

Salinity trends across Florida Bay were mixed last week.  USGS platforms at the eastern creek mouths (W. Highway, Stillwater, Trout) recorded declining salinity over the past week, from the mid-30s down into the teens or mid-20s by Sunday, 6/29.  However, salinity in the eastern Bay proper (e.g., Duck Key, L. Madeira Bay mouth), held in the mid-30s for another week.  Salinity concentrations have been stable in creeks to the west (Taylor River, Mud Creek), further suggesting (as CP stage has also shown) that Taylor Slough will require a good bit of re-hydration before flows make their way south towards the Bay.  The Taylor River (TR) 30 day moving average salinity concentration (used for tracking the FL Bay MFL criterion) dropped to 31.7 psu as of Sunday, 6/29 (down a bit from last week’s reading of 34.5 psu).  Salinity remained stable in the northcentral Bay areas of McCormick Creek. & Terrapin Bay (in the mid-30s) and at the central Bay station in Whipray Basin (in the mid 40s).  In the upstream reaches of Shark River (Tarpon Bay platform), on the other hand, salinity dropped into the single digits last week (down to 6 psu as of Sunday, 6/29), slowly approaching seasonal average concentrations.

 

Water Supply

 

Although there was some rain last week, most of the water fell south of Lake Okeechobee.  Water levels in the upper and lower Kissimmee Basin are now well below their average conditions for this time of year, and approaching their historic lows.  Water levels in the Lower West Coast are now below historical averages, although there was some continued rebound this week.  Water levels in the Lower East Coast are now near historical averages.  Water levels in the Upper East Coast are still slightly above their historic averages, although they also have been declining.  Surface and groundwater levels in Water Conservation Areas 1, 2 and 3 are now near their historic averages, most wells enjoyed a rebound this week.  Water levels in the southernmost portion of Miami-Dade County are now near their historic average levels and rebounded sharply this week.

 

There was also some improvement in the water supply risk indicators since last week.  Six out of the eleven water supply risk indicator parameters are now in the “low” risk category, including the CPC Precipitation Outlook, the Lake Okeechobee Seasonal and Multi-seasonal Net Inflow Forecast, and Water Conservation Areas 1, 2A and 3A.

 

Four out the eleven water supply risk indicators are now in the “medium” risk category, including Palmer Index for Tributary Conditions and LEC Service Areas 1, 2 and 3.

 

Only one risk measure is now in the “high” risk category, the projected Lake Okeechobee Stage (Water Shortage Management Band).

 

LORS2008 (Lake Okeechobee Regulation Schedule)

 

The current Lake Okeechobee stage remains in the Water Shortage Management zone and is unlikely to move back into the Operational Band in the next several months.

 

 

 

 

 

CC:   George Horne