WCA - Everglades Conditions Update

(April 8, 2008)

 

Rainfall:

Residents of the Everglades awoke to the demulcent rhythms of hours of rainfall throughout all basins several nights this week.  Total rainfall ranged from 2.26” to 6.2” in the Everglades (see attached Raindar gif) with the following distribution:

WCA-1:          3.76”               WCA-3A:        4.35”

WCA-2A:       6.2”                 WCA-3B:        2.43”

WCA-2B:       2.26”                ENP:               2.82”

All areas exceeded the mean evapotranspiration for the region of 1.48”.

 

Water Conservation Areas:

While rainfall is generally welcome in a drought, it has continued to interfere with the traditional breeding patterns of wading birds in the Everglades.  Water levels rose throughout the Everglades.  Stages increased the most in northern WCA-3A, where the greatest rain fell, and least in WCA-3B.  Recession rates were very high in all WCAs and in the Park, ranging from 0.05” up to 0.68” (see WCA_stages.xls), producing POOR foraging conditions for wading birds.  (Optimal recession rates are declines of 0.04-0.16’ per week.) 

 

Depths similarly were POOR for wading birds throughout the region, ranging from 0.89’ to 2.56’ in the Conservation Areas.  Wading birds in general need water depths from 0.1’ to 0.79’ to find appropriate prey species.  The current water depths do not support foraging, which is increasing concern for wading bird breeding success this year.  However, as reported last week, it is still relatively early in the nesting season for ibis and it is hoped that these poor hydrologic conditions will have a minimum impact on this species.  More information on nesting is in the Wildlife section of this report.

 

Marsh stages in WCA-1 have risen again and are above Regulation, WCA-2A marsh remains at levels above regulation and canals have likewise risen, and WCA-3A stages have reached the top of zone E1 of the regulation schedule (see Reg_stages.doc), which is designed for protection of the Cape Sable Seaside Sparrow.

 

Everglades National Park:

Everglades National Park and Florida Bay saw substantial rainfall last week, particularly Sunday with 7 day accumulations ranging between 0.7” – 2.6”.  The basin-wide spatially-averaged Raindar totals for the week were 1.8” for the ENP basin and 2.0” in the C-111 basin (see attached gif); precipitation is not accounted for yet in description of stage/salinity trends below. 

 

ENP wetland water levels (see Stages.pdf) showed mixed trends last week, due in part to the timing and distribution of Sunday’s rain event.  Water levels were down in both northern and southern areas of Taylor Slough; at Taylor Slough Bridge daily mean water levels dropped by 4.3” over the week (not unusual for this station, and hourly measurements showed it rising quickly after Sunday’s rain event).  To the south in Craighead Pond, stage decreased by 1.2” for the 7 day period.  In the Shark River Slough system, though, water levels increased by just over 2.5” at station P33 over the week, in response to heavy rainfall in this area over the past 2 wks.  Data from the panhandle (station EVER6) have been unreliable of late.

 

The salinity pattern in Florida Bay and surrounding embayments (see Salinity.pdf) was also variable last week.  Salinity remained just above 30 psu at Trout Creek.  A flow reversal in Taylor River increased salinity into the upper-20s at the mouth and up towards 25 psu in the ponds (at both Pond 5 (USGS station) and Argyle Hendry (ENP station TR)).  As of Sunday, the 30 day moving average concentration at Taylor River, used for tracking the Florida Bay MFL criterion, was at 13.7 psu, up from 9.5 psu last week, and while not unseasonably high, the highest concentration we have seen yet this dry season.  The station at the Little Madeira Bay mouth remains offline. 

 

Strong flow reversals pushed Bay water northward into the north central Bay areas of McCormick Creek and Terrapin Bay, increasing salinity concentrations into the mid-30s.  Data from the central Bay station at Whipray Basin continue to be patchy, so rainfall data haven’t been updated.  In contrast to trends elsewhere in the Bay, and probably the result of local rainfall, salinity in Whipray declined a bit last week to 37 psu over the weekend. 

 

As a whole the regional salinity concentrations are near seasonal norms except out west in areas downstream of Shark River Slough (upstream reaches of Shark River) in Tarpon Bay.  There the daily mean measurement of 19 psu on Sunday is still well above normal for this station, closer to concentrations experienced at the height of the dry season in May, not surprising with the low water levels and flows through SRS this water year.

 

Wildlife:

Spoonbill nesting:

Audubon reported Spoonbill nesting in Eastern Florida Bay at 3 nests, all of which were monitored.  In late March, 1 nest failed and 1 chick survived to 21 days.  In Western Florida Bay, significant colony activity was detected in late January, likely a second nesting attempt by birds at Palm Key.  While they haven’t visited the site yet, they saw more than 40 adults and at least 5 large chicks at the colony.  Audubon staff plan to visit the site this week.  With the rainfall, stages should rise substantially this week.

 

Other wading birds:

The colony flight on Tuesday, April 1, was notable for the absence of wading birds in the northern Everglades.  Scientists counted a total of only 605 nests (585 Great Egret and 20 White Ibis nests),  in sharp contrast to the April counts of 2006 and 2007 when they observed approximately 37,000 and 18,000 nests, respectively (see attached table for more details).  April tends to be the month of peak nesting activity, and we could yet see a late surge in ibis nesting activity if foraging conditions improve soon. However, it is now highly unlikely that storks will initiate breeding.

 

Most areas of the WCAs were largely devoid of birds. Northwest WCA-3A supported moderate numbers of birds, including storks and spoonbills but scientists noted no large foraging flocks. A few large flocks of ibis were observed in western WCA-1 but few birds were seen elsewhere in the Refuge (see nest numbers table for more details).

 

[Note:  Comments from John Ogden and Peter Frederick following this report indicated that there have been other years (1970s and 1980s), following reversals and poor feeding conditions in their usual WCA nesting areas when ibises formed large breeding colonies from May into the summer.  Areas where the nests have appeared before have been identified, including north of Big Cypress and along the southwest coast, as well as L-67, Alley North and Tamiami West; the latter three sites will continue to be surveyed through the usual scheduled flights.]

 

Below is a summary of the nest numbers for each colony. Attached is a survey coordinates spreadsheet, a nest numbers table for comparing nest numbers between 2006, 2007 and this year, and a map showing colony locations. See notes in the nest number table for additional information not provided in this summary. Please feel free to contact Mark Cook if you have any questions.  

 

Alley North Colony

Approx. 35 Great Egrets appear to be nesting at the southern end of island. Approximately 300 pairs have abandoned this colony since last month’s flight.

 

Cypress City

20 Great Egret nests

Again, a reduction on last month’s count

 

6th Bridge

45 Great Egret nests

 

Crossover

No nests

Some foraging was observed under the colony

 

Jetport

No nests

 

Hidden

No nests

10 roosting Great Egrets

 

Tamiami West

No nests

 

Tamiami East

No nests

 

Heron Alley

No nests

 

3B Mud East

No nests

 

Big Mel’

No nests

 

Colony 99

175 Great Egret nests

20 White Ibis nests

 

Colony 73

40 Great Egret nests

 

Colony 70

No nests

 

Colony 111

No nests

 

New Colony 1

No nests

 

New Colony 2

150 Great Egret nests

 

New Colony 3

No nests

 

New Colony 4

120 Great Egret nests

 

New Colony x

?

 

Canal N

No nests

 

 


 

Back to Lake Okeechobee Operations Main Page

Back to U.S. Army Corps of Engineers WSE Homepage