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FS-187-96
U.S. Department of the Interior
Preservation and restoration of the remaining
Everglades ecosystem is focussed on two aspects: improving
upstream water quality and improving "hydropatterns" - the
timing, depth and flow of surface water. Restoration of
hydropatterns requires knowledge of the original pre-canal
drainage conditions as well as an understanding of the soil,
topo-graphic, and vegetation changes that have taken place since
canal drainage began in the 1880's.
The Natural System Model (NSM), developed
by the South Florida Water Management District (SFWMD) and
Everglades National Park, uses estimates of pre-drainage
vegetation and topography to estimate the pre-drainage hydrologic
response of the Everglades. Sources of model uncertainty include:
(1) the algorithms, (2) the parameters (particularly those
relating to vegetation roughness and evapotranspiration), and (3)
errors in the assumed pre-drainage vegetation distribution and
pre-drainage topography. Other studies are concentrating on
algorithmic and parameter sources of uncertainty.
In this study we focus on the NSM output
-- predicted hydropattern -- and evaluate this by comparison with
all available direct and indirect information on pre-drainage
hydropatterns. The unpublished and published literature is being
searched exhaustively for observations of water depth, flow
direction, flow velocity and hydroperiod, during the period prior
and just after drainage (1840-1920).
Additionally, a comprehensive map of soils in the
Everglades region, prepared in the 1940's by personnel from the
University of Florida Agricultural Experiment Station, the
U.S. Soil Conservation Service, the U.S. Geological Survey, and
the Everglades Drainage District, is being used to identify
wetland soils and to infer the spatial distribution of
pre-drainage hydrologic conditions. Detailed study of this map
and other early soil and vegetation maps in light of the history
of drainage activities will reveal patterns of change and
possible errors in the input to the NSM. Changes in the wetland
soils are important because of their effects on topography (soil
subsidence) and in their role as indicators of hydropattern.
The objectives of this study are:
Aldo Leopold wrote that "the first step in
intelligent tinkering is to save the pieces." For the
Everglades, saving the ecosystem pieces would have meant making
synoptic stage and flow measurements over multiple years and over
an area larger than the State of Connecticut, prior to launching
even the first canal dredge. Unfortunately, but understandably,
this was not done. For the first 40 to 60 years of drainage very
few standard hydrologic measurements exist. Evaluation of a
hydrologic "hindcasting" model such as the NSM must, therefore,
rely on more than the traditional sources of information. There
are numerous sources of hydrological information which merit full
exploitation, but they are often in unusual locations, may be
unpublished, and sometimes require further interpretation and
analysis. Examples of historical sources include early maps,
government surveys, botanical explorations, road and canal
profiles, cross-Everglades expeditions, military accounts, and
early scientific investigations.
Vegetation: Sufficient references to vegetation have been found to permit annotations and improvements to a 1943 vegetation map. Estimation of characteristic sizes of components of the pre-drainage vegetation mosaics will be possible. Soil change: In addition to soil subsidence in known areas as well as in previously undocumented ones, it appears that, prior to 1946, the nature of the soil profile changed measurably throughout vast areas of the sawgrass plains. This sheds further light on pre-drainage hydropatterns.
Products will include:
Click here for a printable version of this fact sheet (note: document will
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Click here for a PDF version of this fact sheet (available from the Water Resources of Florida website). PDF files require the Free Adobe Acrobat Reader ® to be read. Environmental Defense Fund SOFIA Project: Comparison of the South Florida Natural System Model with Pre-canal Everglades Hydrology Estimated from Historical Sources |
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 05 November, 2004 @ 03:04 PM(TJE)