WCA - Everglades Conditions Update
(Jan. 8,
2008)
Rainfall:
Despite
the 0.5” – 1.0” of rain along the southeast coast, rainfall this past week has
been slight across the Everglades (see Raindar.gif). The greatest amount of
rain received by a WCA was 0.083” in WCA-3B. The least amount of rain was 0.03”
in WCA-2A. Rainfall totals over the holidays were also very light across ENP & FL Bay. Sporadic, quick-moving
showers were the rule across much of the ENP (with most daily precip totals
measuring well below 0.1”). With an average pan evaporation of 1.03”,
this was another deficit water budget week (see srs.pdf).
Water Conservation Areas:
GOOD
dry-season recession rates (averaged over the last three weeks) continue to
dominate the region (see WCA_stages.xls).
WCA-3B was the only area where recession rates were FAIR due to little change
over time. Although recession rates were GOOD, the depths in the Everglades remain too deep for wading bird foraging. This
is normally not an issue at this time of year because foraging in support of
nesting behavior does not usually begin until February. Only the NW corner of
WCA-3A had proper depths and recession rates to support wading birds. However,
birds are not using this area. It may be that fish prey are not available
(NOTE: Last year’s drought caused an 80% reduction in food, compared to the
previous high-nesting-success year, for wading birds across the system).
Stages in WCA-1 are slightly below at Regulation, WCA-3 stages continue to be significantly
below regulation, and WCA-2A remains above regulation (see WCA_reg_stages.doc).
Everglades National
Park:
Light
rainfall over the holidays allowed ENP wetland water levels to continue to
decline. In general, stations in the northern part of the system saw more
substantial declines than those to the south. Not surprisingly recession
has been most dramatic at Taylor
Sl. Bridge
where water levels have dropped by 6” (0.5’) over the past 3 wks. Shark River
Slough water level, as measured at P33, dropped by 2.2” over the past 3 wks.,
& by nearly 0.75” over the past 7 days. Overall water levels at these
2 stations (TSB & P33) are well below average for this time in the dry
season, in part because neither area came close to their respective seasonal
high water levels during the 2007 rainy season. To the south water levels
are slightly below average at Craighead Pond (station CP) & in the
panhandle at EVER6.
Several of
the marine monitoring stations have not transmitted data over the past
week. Overall, though, using what data are available (through USGS
platforms & a few ENP stations that are online) it seems that FL Bay
salinity as a whole remains fairly low for this time of year. Salinity
concentrations at Trout Ck. have generally remained in the mid-20s, while
concentrations at Taylor
River mouth have been
slightly lower in the mid-teens. In the Taylor River
ponds salinity has generally remained low (near 1 psu). In the north-central
Bay, salinity in Terrapin
Bay and McCormick Creek
ranged between the teens & low-20s. In central Florida
Bay, Whipray Basin
salinity continued to hold below 30 psu for the entire 3 wk. period, a good
gauge of conditions across the area. In the SRS outflow at Tarpon Bay,
salinity increased from single digits to just above 10 psu as of 12/31. The Bay
continues to be well buffered in terms of salinity for the dry season.
Wildlife:
Nesting
behavior surveys will begin in February. For now, foraging observations are
qualitative, but important. Spoonbills and white ibis are foraging extensively
in the STA’s. Ibis are also feeding in the western sections of WCA-2A (Note:
The topography in WCA-2A is such that despite depths over 1 ft at the 2-17
gauge, the depths for foraging can be FAIR to GOOD in the west and NW of
WCA-2A). Information provided by staff at Audubon’s Tavernier
Science Center
(Brynne Langan & Jerry Lorenz) indicates a historic low number of spoonbill
nesting attempts in Florida
Bay, both in the
northwest & northeast portions of the Bay. In the northwest (birds
that forage on Cape Sable), there are ~ 80
nests on Sandy Key, whereas the long-term average (since monitoring began in
the late 1980s) is well above 150 nests at this colony. Perhaps more
striking is that there are no nests as of yet at what is typically the largest
northeast colony at Tern Key (where there have always been at least 60 nests,
average of nearly 100). It is unclear why birds have abandoned Tern Key
for nesting this season. Water levels are only slightly lower than
average in the southern Everglades, where
these birds forage, & recession rates do not appear to be abnormally high
or low. Low nest numbers in both the northwest & northeast part of
the system suggests something more than water management is
affecting nesting behavior of Florida
Bay spoonbills this
season.
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