jurisdiction (Bureau of Land Management [BLM],
ponded water only during exceptional years, such as
NRCS). To the extent possible, all relied on the pres-
the El Nio period of 1998.)
ence of water as a primary indicator, and best profes-
Dugway Proving Ground, Dugway, Utah
sional judgement incorporating drift lines, aerial photo-
graphs, USGS maps, and anecdotal evidence by local
Because areas of the playa (Lichvar et al. 1995)
experts. Albuquerque district used crusts (presumably
known to become inundated generally lacked one or
both biotic and non-biotic) as well. Sacramento district
more of the three parameters of a wetland, the OHW
incorporated evidence of wildlife use as well as a tran-
line was used to determine jurisdictional limits. OHW
sition from Salicornia and other halophytes to unveg-
was determined by ponded water or combinations of
etated surfaces.
other indicators, including mud cracks; drift lines;
phreatophytic vegetation; topography; salt crusts; and
color, bulk density, and texture of the soil.
CASE STUDIES
Edwards Air Force Base, California
Primary indicators
Major playas include Rosamond, Buckhorn, and
Ponded water was used as a primary indicator.
Rogers (Lichvar and Sprecher 1996, Brostoff et al. 1996).
Drift lines composed of various types of debris
A stepwise process was used to distinguish between
material, which were generally observed only in
wetland, non-wetland WoUS, and unregulated areas: 1)
localized areas and not as a continuous feature
determine if the area had one or more primary indica-
around the playa boundary, were also used as
tors of OHW developed for the area; 2) areas lacking a
evidence of previously ponded water and thus the
primary indicator were eliminated from further consid-
OHW boundary.
eration as a WoUS; 3) areas having a primary indicator
The landscape in pre-defined sampling areas was
were evaluated for indicators of a three-parameter wet-
evaluated for its potential to pond water; those
land. If not, the area was determined to be a WoUS. The
zones that were flat and not drained by intermit-
delineation also involved development of a range of
tent channels were assumed to pond water. This
evidence for indications of OHW described below.
was broadly verified by the observation that
Identification and calibration of surficial indicators
ponded water was frequently observed in flat areas
was predicated on analysis of precipitation records from
with a hard, gray aspect. Similarly, because sur-
1941 to 1995 and aerial photographs from April and
face water was observed inside drainage areas on
August 1992. The former set of photos corresponded
the playa, these drainage areas and depressions
to a rainfall history at the 95th percentile level, the latter
were rated as reliable indicators. Sloped and highly
to a 50th percentile level. OHW determinations were
eroded areas at the edge of or within the playa itself
made by compiling and then evaluating the surface char-
were excluded.
acteristics of the playas and dry washes. Ponded water
Soils with moist matrix colors of 10YR 7/1 to 8/2
and the potential indicators that developed after dry-
and high silt contents were found only in the playa.
ing were followed over several months. Indicators were
Low bulk density soils were found only on soft
then assigned a rating of primary, one that is consis-
playas and thus used as a negative indicator of
tently reliable for assessing the location of OHW in the
inundation.
field at EAFB; and secondary, for those indicators that
were either less reliable or found occasionally in upland
Secondary indicators
landscape positions. Traditional indicators, such as drift
(1) Mud cracks ranging from polygonal to open and
lines, were used in addition to unconventional indica-
lined were common. The former type was observed in
tors. These included features that had been document-
the presence of ponded water and soil mottles; the lat-
ed in the geomorphic literature as indication of previ-
ter type was interpreted as occurring near the edge of
ously standing water: mud crack styles, reddish-brown
the OHW. (2) The unvegetated areas between mounds
of phreatophytic vegetation (Allenrolfia occidentalis)
stains, and biotic crusts. Considerable attention was
paid to the nature of soil crusts; while a few specific
were assumed to pond water. (3) Because the origin of
crust types were consistently associated with stand-
salt crusting is ambiguous it was rated as a secondary
ing water, both bacterial- and algal-dominated crusts
indicator. (4) Soil texture is a negative indicator in that
occurred in previously inundated areas. The black, pedi-
soils with high sand content (>50%) were not found on
cled, cryptobiotic crusts were negatively associated
the playa except as nonjurisdictional sand dunes.
with standing water. (Note that in later work Brostoff
Twentynine Palms
and Rundel [1998] and Lichvar [personal observation]
found rare occurrences of black crusts in areas that
The largest playas on the base at the U.S. Marine
20
to contents
Previous Page
