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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