2000
Research report
- Determinants
of Reproductive Success in Female Red Kangaroos
- Wildlife
Tourism with Rangeland Kangaroos: Product development and
implementation
- Willy
Willies in the Australian Landscape: Environmental Controls
and Dust Transport Characteristics
- Vegetation,
hydrology, and erosion mechanisms in arid zone streams and
shrublands
- The
Western NSW Archaeological Program (WNSWAP) at Fowlers Gap
- The
Roles of Mitochondria and Capillaries in Determining the Maximum
Aerobic Capacity of Red Kangaroos (Macropus rufus)
- Thermoregulation
in Juvenile Red Kangaroos (Macropus rufus) after Pouch
Exit: Higher metabolism and evaporative water requirements
- Acquisition
and analysis of rainfall and waterborne pathogen data from
Fowlers Gap
- Surveying
at Fowlers Gap Using Rapid Static and Kinematic Stop-Go Geodetic
GPS
Determinants of Reproductive Success
in female Red Kangaroos.
Investigators: Amanda Bilton and David Croft, School of Biological Science, UNSW
Over
the past three years information on the reproductive success of
at least 33 radio-collared, free-ranging female Red Kangaroos
on Fowlers Gap has been collected. Of the 102 young known to be
born during this period, only one-third survived to weaning, the
remaining two-thirds dying before 12 months of age.
With
a weaning rate of only 0.43 young per female per year, and an
average reproductive life span of 7.55 years, the expected lifetime
reproductive success of a female Red Kangaroo on Fowlers Gap was
calculated to be 3.3 young in a lifetime. Based on the reproductive
life-history traits of these animals, they are in fact capable
of rearing a maximum of 7.6 young to weaning in an average lifetime.
Thus female Red Kangaroos on Fowlers are only achieving 40% of
their maximum reproductive potential.
Results
so far suggest that environmental conditions, in particular, rainfall
and the abundance of good quality feed (esp. green grass), have
a significant impact on the survival of young to weaning. It was
found that those females that successfully reared their offspring
to weaning were doing so at times when the amount of green grass
available in the habitat, and the rainfall over that period, was
significantly higher than for those females that lost their offspring.
Given the highly dependant relationship between rainfall and plant
growth in the semi-arid regions of Australia, and the high energy
and nutrient requirements of growing young, it fits that the survival
of the young is greatest during times of relatively good pasture
conditions.
Sex
of the offspring also seems to play an important role in the scheduling
of maternal reproductive effort. Those mothers weaning male offspring
were older than those weaning female offspring, a life-history
trait also observed in the Eastern Grey Kangaroo. Also, those
mothers successful at rearing male offspring to the stage of permanent
pouch exit, 8 months, were doing so at times when there was more
green grass available in the habitat compared to those mothers
rearing females. These results suggest that females may manipulate
their investment in male or female offspring according to the
relative costs and benefits of rearing the different sexes. Continuing
work on maternal care and behaviour will hopefully elucidate to
what degree the sex of a mother's young may affect her lifetime
reproductive success.
The
importance of this research lies in its contribution to a more
thorough understanding of Red Kangaroo population composition
and dynamics; and its application in terms of population modelling
and management will be vital to the process of ensuring the sustainable
use of this species.
Wildlife
Tourism with Rangeland Kangaroos: Product development and
implementation
Investigators: David
Croft, School
of Biological Science, UNSW
The
large populations of kangaroos in the boundless expanses of the
outback will be used to build a unique tourist experience, comparable
to an African game-viewing safari, but with animals and a safe
healthy environment unlike anything found elsewhere. This project
focuses on the far west of NSW, which offers both high abundance
and diversity of large kangaroos, as it supports Australia's greatest
densities of red kangaroos and euros alongside smaller populations
of eastern and western grey kangaroos. Large protected areas,
especially Sturt National Park, are set aside for their conservation
but pastoral leases also support kangaroo populations. An attitudinal
survey of visitors to the region demonstrated a strong attraction
to wildlife tourism based around kangaroos, and demand for products
to enhance knowledge and the quality of viewing opportunities.
Fowlers Gap (UNSW arid zone field station) and Sturt National
Park will create such products based on the best designs in arid
lands in Africa and elsewhere. The objectives of this project
are: (1) to research product designs for access ways, viewing
platforms, interpretative materials and accommodation to create
and support a high quality experience in wildlife tourism with
kangaroos (2) to test market the products to clientele derived
from education groups (Study Abroad), alumni and a local operator
at Fowlers Gap and to trial some products with Sturt National
Park visitors, (3) to assess patterns of usage and visitor satisfaction
with the products, (4) to assess and apply remedial action to
any adverse impact on wildlife or habitat through the tourism
enterprise created around the products, and (5) to create a model
for wildlife tourism enterprises on public and 'private' lands
in the rangelands, and (6) to promote the products to stakeholders
from the National Parks and Wildlife Service, pastoral leaseholders,
local and national tourism operators from the development site
at UNSW arid zone field station, Fowlers Gap. The main outcome
will be to underpin tourism ventures in the region with well-researched
products that create new demand for wildlife tourism and strong
visitor satisfaction.
Work
competed in 2000 includes guides to the flora and fauna encountered
along the eco-trails on Fowlers Gap and the Olive Downs walking
trail at Sturt National Park, guides to the kangaroos of Fowlers
Gap and Sturt National Park, checklists of amphibians, reptiles,
birds and small mammals for both sites, and a checklist of plants
at Fowlers Gap. Wildlife viewing platforms have been constructed
in the form of a bird hide at Lake and a hide at a night-illuminated
water hole in Connors at Fowlers Gap. Adaptive re-use of surplus
pastoral infrastructure such as homesteads and Shearer's quarters
has been investigated with the Tibooburra Area of NPWS for development
in 2001.
Publications:
Croft, D.B. (2000). Sustainable use of wildlife in western New
South Wales: Possibilities and problems. Rangeland Journal 22, 88-104.
Return to index
Investigators: Alison Curl, David Dunkerley,
and Nigel Tapper.
S
chool of Geography and Environmental Science,
Monash
University
, Clayton, VIC 3168.
An
extensive census and sampling program conducted on the Fowlers
Gap Research Station provided quantitative information on willy willy characteristics and environmental constraints. Willy willies are
local convective circulations visually defined by the entrainment
and transport of dust and surface debris. They are common in most
Australian arid and semiarid landscapes and their American counterpart
the ‘dust devil’ has been observed in the Mojave Desert, California (Maxworthy, 1973) and the arid lands around Tucson,
Arizona (Sinclair, 1973) . Willy willies
are potentially significant geomorphic agents in
Australia
given the slow rate of the erosion processes active across large
areas of the continent. Despite this potential significance very
little is known about these atmospheric phenomena, with only one
other study having been completed in
Australia
.
Given the lack of understanding in this field, the study completed
at Fowlers Gap constitutes an exploratory rather than definitive
study of the characteristics of willy willies in the Australian semiarid landscape.
A
20-day census was conducted from
the 16th of January 2001
to
the 4th of February 2001
in
a 35-km2 study area on the lower eastern slopes of
the
Barrier
Range
.
The results from the census in which 557 willy willies were observed, indicated that willy willy frequency, size, shape and duration vary according to
local environmental conditions. An air temperature lapse rate, measured between 12 and
252 cm of the surface, of 0.9 °C m–1 was required for the initiation of the willy willies, with the frequency increasing with lapse
rate. Willy willies were also found to be restricted to wind speeds
between 1.5 and 7.5 m s-1, with some wind required
for their initiation but too much shearing the tops off the columns.
Analysis of the spatial distribution of willy willy initiation sites with respect
to vegetation cover of the study area showed that willy willy frequency increases with decreasing surface cover. Very
few willy willies
were observed in the thick tussock grassy areas compared to areas
with exposed bare ground.
In
addition to the census, the dust being transported in the lower
160 cm of 20 willy willies was sampled using a tape-based vertical profile sampler
developed as part of this study. The analysis of the samples using
visual based digital analysis method revealed that almost 40%
of the particles counted were being transported within the first
5 cm of the columns and over 80% overall were between 6 and 63 mm
in major axis diameter. The results from this analysis when considered
in terms of the characteristics of the surface being traversed
during sampling show that the sediment load carried in the willy willies increases with decreasing vegetation cover.
The
increased frequency and sediment loads of willy willies with decreasing vegetation combined with the
preferential entrainment of silt sized particles could, over time,
make willy willies a potent mechanism for the local differentiation
of surface textures. Willy willies may be contributing to the
maintenance of the patchy plant cover that characterises much
of inland
Australia
.
Their increase in frequency and sediment carrying capacity with
decreasing surface cover indicates that they may also become more
potent with increasing aridity either during drought or with a
movement inland into
Australia
’s
arid core.
References:
Maxworthy, T. (1973). A vorticity source
for large-scale dust devils and other comments on naturally occuring columnar vortices. Journal of the Atmospheric Sciences 30, 1717-1722.
Sinclair,
P.C. (1973). The lower structure of dust devils. Journal of the Atmospheric Sciences 30, 1599-1619.
Return to index
Investigators:
David
Dunkerley
School
of Geography and Environmental
Science,
Monash
University
Victoria
3800
Across
the extensive low-gradient landscapes that occupy much of the
Australian arid and semi-arid lands, surface runoff is developed
episodically during heavy rains. Despite the gentle slopes, the
runoff provides an important agency for the movement of litter,
seeds, and eroded soil particles. Runoff redistributes surface
water and so influences the distribution of soil moisture within
the landscape.
Despite
these important roles, relatively little is known in detail about
the landscape characteristics that control the speed of surface
runoff or influence its capacity to entrain and carry sediment.
Furthermore, relatively subtle variations in soil microtopography,
infiltration capacity, and litter abundance appear to be critical
in deciding whether an area of sloping landscape sheds runoff downslope or absorbs runoff arriving
from upslope. There are many landscapes in the Australian drylands where plants grow in patchy communities related to such patterns
of runoff and runon.
Using
both field experiments based at Fowlers Gap, and laboratory experiments
using natural plant litter collected there, the properties of
shallow overland flows have been investigated. There are significant
challenges in measuring the depths and speeds of flows that may
be as little as 0.2 mm deep, resulting from small rain events.
A new measuring system, comprising a computer- controlled XY gantry
as well as a Z (elevation) sensor, has been developed for use
in studying such features. The system allows runoff depths and
soil surface elevations to be recorded at any number of nominated
grid points lying within a runoff plot, with a depth resolution
of 25 µm. During a series of experiments, litter loadings have
been manipulated, and flow rates varied, on experimental plots
sloping at about 1.2 degrees. From the measured flow characteristics,
parameters such as the Darcy-Weisbach friction coefficient can
be determined.
Results
to date have shown that plant litter can reduce runoff flow speeds
significantly more than an equal cover of quart stones, another
common soil surface feature in the Australian drylands.
Indeed, under some flow conditions, it has been shown that the
stones actually increase runoff flow speeds, by channelling the
flow across a narrower zone of soil lying between the stones.
Results of this kind are helping to shed light on the generation
and movement of surface runoff. They are also highlighting the
important role played by seemingly minor features of the landscape
– the residual organic litter and the veneers of surface stones
(gibbers).
The
experimental program is continuing, and further experiments with
the measuring gantry are planned for Fowlers Gap in 2001/2002.
Publications:
Dunkerley D.L. (2000). Flow hydraulics in laminar flows, the starting point
for interrill sediment erosion and transport.
Abstracts, 9th Australian and
New
Zealand
Geomorphology
Conference, Wanaka NZ 11-15 December
2000, p.25
Dunkerley D.L. (2000). Water redistribution by runoff and runon in semi-arid mosaic landscapes – how does it work? Abstracts, 9th Australian and
New
Zealand
Geomorphology
Conference, Wanaka NZ 11-15 December
2000, p.26
Dunkerley D.L. (2001). Estimating the mean speed of laminar overland flow using dye injection
-uncertainty on rough surfaces. Earth Surface Processes
and Landforms 26(4), 363-374.
Dunkerley D.L. Domelow P. and Tooth D. (2001). Frictional retardation of laminar flow by plant litter and surface
stones on dryland surfaces: a laboratory study. Water Resources Research, 37(5), 1417-1424.
Thiery J.M. Dunkerley D.L. and Orr B. (2001). Landscape models for banded vegetation genesis. pp.167-197 in
D.J. Tongway, C. Valentin and J. Seghieri (Eds.) Banded vegetation patterning in arid and semiarid environments.
New York
: Springer Verlag, 251pp.
Seghieri J. and Dunkerley D.L. (2001). Specific methods of study. pp.32-51 in D.J. Tongway, C. Valentin and J. Seghieri (Eds.) Banded vegetation patterning in arid and semiarid environments.
New York
: Springer Verlag, 251pp.
The
Western NSW
Archaeological
Program (WNSWAP) at Fowlers Gap
Investigators: Trish
Fanning(1) and Simon Holdaway(2)
(1)Graduate
School
of the Environment,
Macquarie
University
,
Sydney
(2)Department of Anthropology,
University of Auckland
,
New Zealand
The
Western NSW Archaeological Program (WNSWAP) was initiated in 1995
to investigate Aboriginal stone artefact scatters in a landscape
context. Techniques based
around the close integration of archaeological and geomorphological data sets using electronic survey technology and Geographic Information
System (GIS) software were developed over a four-year period at
Mt Wood in
Sturt
National
Park
. We then moved to Fowlers Gap in order to apply
these techniques to investigating the Late Holocene archaeological
record in one location with a variety of landscapes as a way of
assessing variation in Aboriginal occupation intensity, mobility
and resource use. Pilot surveys in 1999 lead to the selection
of six upland land systems for more detailed investigation in
subsequent years.
During
a four week field season in June, 2000, our team of student volunteers
from Auckland University in New Zealand and Macquarie University
in Sydney, assisted by Ray O'Donnell and Paul Menz from Broken Hill Local Aboriginal Lands Council and Dr Dan Witter,
now retired from the NSW National Parks and Wildlife Service,
surveyed and logged around 7,500 artifacts at three locations: Sandy Creek gorge (Nundooka Land System), downstream of Nelia Dam (Sandy Creek Land System), and on Fowlers Creek
upstream of the Gap (mapped as Nuntherungie Land System, but more in common geomorphologically with Old Homestead Land System). In addition, we took advantage of a rather unique situation
by undertaking a repeat survey of an area in
Sandy
Creek
gorge that we
had previously logged in 1999. We did this because, in February 2000, one of the largest
rainfall events on record was experienced. We wanted to see if we could detect any changes to the
artefact densities and distribution that might have occurred as
a result of erosion triggered by a large magnitude storm event. We also described and sampled charcoal from the remains
of 30 heat retainer hearths, and sent these samples to the Waikato Radiocarbon Laboratory in
New Zealand
for radiometric dating.
Analysis
of the results of the artefact surveys has confirmed our first
impressions that the stone artifacts are not randomly nor uniformly distributed across the landscape,
but are clustered in different ways in each land system investigated,
reflecting the different ways in which Aboriginal people interacted
with the varied landscape in the past. For example, artifacts on the Fowlers Creek study site are manufactured
predominantly from quartz nodules that are available locally. Those from the Nundooka Land System, are made from a variety
of materials, some of which were brought to the location from
sources several kilometers distant. These
differences may represent differences in the activities performed
at different places in the landscape but they also reflect differences
in the length of occupation at these places. More complex sets of artifacts represent places that were returned to more often and were used
for longer periods when compared to locations that have less varied
artefact assemblages.
The
most interesting and exciting results, however, come from the
radiocarbon dating of the hearth charcoal samples. They demonstrate that Aboriginal people repeatedly
occupied certain areas on what is now Fowlers Gap Station throughout
the mid to late Holocene. The
oldest date obtained so far is 5243 ± 164 y BP from the Fowlers Creek study site, and the youngest
is less than 200 years old (i.e. modern) from the Nelia Creek study site. However,
it is not the time span of these dates that is of most interest,
but the pattern of dates in relation to the inferred ages of the landsurfaces on which the hearths and
associated artifacts are found. On landsurfaces where geomorphic
processes of erosion and deposition are relatively active, such
as the apex of the Nelia Creek floodout, and the channel marginal elements of Sandy Creek
gorge, the dates are relatively recent and the record relatively
short, reflecting the dynamic geomorphic environments at these
locations, whereby sediments accumulate over short periods of
time, perhaps a few hundred years, and are then removed by erosion
during infrequent, high magnitude flood events. By contrast, the longest record is found on the relatively
stable terrace surface adjacent to Fowlers Creek, reflecting the
relatively less active geomorphic environment at this location.
But
even here, the record is not continuous: apart from the 5243±164
y BP date, there is a cluster of eight dates between 3661 and
3130 y BP, one at 1857±62
y BP, one at 898± y BP and one at 213±40
y BP. This suggests that
Aboriginal people moved into and out of the region throughout
the mid to late Holocene, occupying areas that had not been occupied
for several centuries. This contrasts with the commonly held view from
elsewhere in
Australia
that Aboriginal occupation of some regions was more or less continuous
from the late Holocene onwards, reflecting increasing population
and a more sedentary lifestyle. On the contrary, our research shows that, at least in the
area around Fowlers Gap, Aboriginal hunter-gatherer groups remained
relatively mobile, moving away from then back into previously
occupied areas on a fairly regular basis throughout the mid to
late Holocene and right up to the time of European contact around
250 years ago.
Confirmation
of this pattern of land use and mobility will be sought from further
radiocarbon dating of hearth charcoal collected during the 2001
field season. We eagerly
await the results, and will report them in the next Fowlers Gap
Field Station annual report.
Investigators: Brock Misfud and
Terence
Dawson
School
of Biological Science, UNSW
Sydney 2052
Red
kangaroos (Macropus rufus)
are perceived to be highly athletic mammals since they have an
efficient mode of locomotion. However, it is possible they also
have a high aerobic capacity as evidence suggests they have a high mass-specific maximal oxygen consumption ( O2max)
and the appropriate cardiovascular characteristics to go with
it. In placental mammals, total mitochondria and capillary volumes
have been shown to be strong indicators of aerobic capacity. To
gain further insights into the aerobic capacity of red kangaroos,
we investigated the capillary structure and mitochondrial capacities
of red kangaroo heart and skeletal muscles. The red kangaroo had
a high whole body mass specific mitochondrial volume (37.5 ml.kg-1)
similar to other athletic species, such as the dog (40.6 ml.kg-1; Hoppeler et al., 1987),
and much greater than less athletic species, such as the goat
(13.8 ml.kg-1; Hoppeler et
al., 1987). Although capillary length density varied proportionally
with mitochondria volume density, specific capillary length (221
km.kg-1) and specific capillary volume (3 ml.kg-1)
were low in comparison to both athletic and less athletic species.
Therefore, it is suggested that the red kangaroo uses other physiological
mechanisms to match capillary O2 supply with mitochondrial
demand, such as high hemoglobin concentration during exercise and, possibly, a
higher pressure difference for O2 diffusion in the
capillaries. In regard to mitochondria and capillary structure
within the kangaroo, the heart has the greatest mitochondrial
and capillary volume, reflecting its important role in continuous
and variable transport of O2 to muscles. Interestingly,
the multifidi lumborum, a large back muscle, had relatively high
mitochondrial and capillary volumes when compared with the other
skeletal muscles. This muscle has an important tail counterbalance
function during hopping. Overall, the data suggests that a high
mitochondrial capacity in the red kangaroo is an adaptation, which
facilitates a high aerobic capacity. However, the delivery of
oxygen from the capillaries needs further examination in order
to complete our understanding.
Return to index
Investigators: Adam
Munn and
Terence
Dawson
School
of Biological Science, UNSW Sydney 2052
The
population dynamics of red kangaroos (Macropus rufus) in the Australian arid zone is tightly linked with
environmental factors, which partly operate via the survival of
juvenile animals. A crucial stage is the young-at-foot (YAF) stage
when kangaroos permanently exit the pouch. We have examined the
thermal biology of YAF red kangaroos during ages from permanent-pouch-exit
(PPE) until weaning. Over a wide range of environmental temperatures
(Ta -5°C to 45°C) YAF red kangaroos had a mass-specific
metabolism that was generally twice that of adults, and considerably
higher than would be expected for an adult marsupial of their
body size. The total energy requirements of YAF red kangaroos
were 60 –70% of those of adult females, which were three times
their size. Over the same range in Ta YAF red kangaroos
also had total evaporative water losses equal to those of adult
females. At the highest Ta, 45°C, differences were
noted in patterns of dry heat loss (dry conductance) between YAF
red kangaroos and adult females, which may partially explain the
relatively high levels of evaporative cooling by YAF. By weaning
age young kangaroos showed little change in their basal energy
and water requirements (at Ta 25°C), but did show reduced
mass-specific costs in terms of energy and water use at extremes
of ambient temperature (-5°C and 45°C respectively). In their
arid environment, typified by unpredictable rainfall and extremes
of Ta, young red kangaroos may need to remain close
to water points, in turn restricting their ability to find the
high quality forage needed to meet their high energy demands.
Return to index
Acquisition
and analysis of rainfall and waterborne pathogen data from
Fowlers Gap.
Investigators: Ian Cordery, Jerry Ongerth,
Jim Tilley and
Alf
Wojcik
School
of Civil and Environmental Engineering, UNSW
Sydney
2052
Arid
Zone Rainfall and Runoff
In early February 1999,
Jim Tilley (
PO
, Civil & Environmental Enginering (C&EE), UNSW) installed
new automatic rainfall monitoring equipment at four of 11 historic
Water Engineering rainfall recording sites at Fowlers Gap. Historic
rainfall and runoff data are available from 17 sites through 1989,
including 11 pluviometer and runoff plot sites
as well as 6 water storage recording sites. The current four rainfall
sites are at Sandstone West (the old Frieslich Mort site), Nelia III plot site, Mating
large plot site and the
North Mandleman
large plot site. Previous observation indicates that a denser
network of rainfall sites would provide for more sophisticated
hydrologic analysis. However, the current sites were chosen to
provide a baseline consisting of a north-south and east-west cross
sectional representation of rainfall at the Station. The continuation
of monitoring provides an important continuing data base on rainfall-runoff
relationships in the arid zone of western
New
South Wales
.
The
four existing instruments are tipping bucket rain gauges complete
with data loggers. These instruments require operator inspection
at a minimum of quarterly to check on their operation and retrieve
data after events as required. The data loggers record the time
and date of bucket tip. At present, station staff
remove the loggers and replace them with units posted out
from Kensington and return the used units to Kensington to download
and disseminate the data. The data is stored in the School's large
HYDSYS time series database and can be accessed from there to
forward to the station for on site records or to others on campus
as required. The data is available electronically for insertion
into spreadsheets etc. or as hard copy graphs etc. directly from
HYDSYS.
Data
from the above system have been recorded since mid February, 1999.
Data from the recent period have been incorporated into technical
publications prepared by Professor Ian Cordery (see below). Data can be obtained by special arrangement by contacting
Mr. Alf Wojcik, P.O. at the School of Civil and Environmental Engineering, (02) 9385 5025, 0415 271 723, or a.wojcik@unsw.edu.au.
Future
plans include submission of quotations, to the management committee,
for a complete compact weather station to be installed at the
site of the old homestead weather station. This would use a data
logger on site connected, if required, to a PC in the office for
instant read outs and/or alarm conditions. Technology has moved
a long way in the last decade or so such that the current cost
of a state of the art, simple to operate, weather station is now
only a fraction of the cost of the original weather station installed
in the early 1980's. Likewise telemetry is now another real option
to be investigated that would be capable of connecting all the
outlying sites to the same system.
Catchment
Management for Pathogen Control
In
September of 2000, Jerry Ongerth (A.
Professor, Water Engineering, C&EE, UNSW) traveled to Fowlers gap to collect animal faecal samples to
determine the presence and characteristics of protozoan cyst-forming
pathogens, Cryptosporidium and Giardia. These organisms
are wide-spread infecting agents common in domestic animals and
responsible for outbreaks of waterborne gastrointestinal illness
in many parts of the world. Dr. Ongerth’s current work is focussed on identifying pathogen
subgroups identifiable by molecular typing (Doctoral studies of
S. Blasdall
, C&EE, UNSW), and studying the host
population specificity of pathogen subtypes. Additional interests
include identifying major attenuation and transport mechanisms
relating pathogen production by domestic animal herds to pathogen
loading in local surface water.
Results
of the September, 2000, sampling indicate that sheep, feral goats and kangaroo populations at Fowlers Gap
all carry both Cryptosporidium and Giardia. The
prevalence found is similar to that found in the same species
in non-arid areas elsewhere both in
Australia
and overseas. Further, molecular typing indicates that the Cryptosporidium type carried by Fowlers Gap sheep is shared by both red and grey
Kangaroos.
Publications:
Cordery,
I.
and Fraser,J.,
2000 "Some hydrological characteristics of the Australian
arid zone". Int. Conf. on Integrated Water Resources Management,
Roorkee
,
India
,
Dec. 19-21, 611
-616.
Cordery,
I.
and Fraser,J.,
2000 "Characteristics of rainfall and transmission losses
in the Australian arid zone". Hydro2000, 3rd Int. Hydrology
and Water Resources Symp.,
Perth
,
Nov. 20-23, 701
-705.
Ongerth, J.E., Blasdall S. A., and Fisher, M..,
2001. “Characteristics of Cryptosporidium in Domestic and Wild Animals,
New
South Wales
and
Victoria
,
Australia
”. International Cryptosporidium Conference,
Fremantle
,
WA
,
October
8-12, 2001
.
Return to index
Investigators: Gresley Wakelin-King(1), Ken Johnston(2), Alisdair Walker(2), Phil Collier(2)
( 1)Dept. Earth Sciences, La
Trobe
University
, Bundoora, Vic. 3088
(
2)Dept. Geomatics,
University
of
Melbourne
,
Parkville
, Vic. 3052
As
part of a larger project investigating the geomorphology, landscape
history and fluvial process of Fowlers Creek, a geodetic-quality
GPS (Global Positioning System0 survey was undertaken in 1999
and the results analysed in 1999 & 2000. Sites surveyed included
pre-existing sample locations, previously marked with star pickets;
and the flat country in and around the creek’s terminal fan. In
addition, a number of permanent survey markers
had their eastings and northings established (heights being known) or their full coordinates established
(Table 1). The project was commissioned and supported by GWK, and two final-year Geomatics students
(KJ & AW) collected data in the field, and processed the results
in
Melbourne
under
the supervision of PC.
The
large area under investigation, combined with the line-of-sight
problems presented by the creek’s treeline,
would have made it difficult to collect the desired data by standard
(EDM theodolite) surveying in any feasible timeframe; making GPS
an attractive alternative. However, because of the very low relief
of the landscape, a high degree of vertical accuracy was desired.
Geodetic-quality GPS is fundamentally different to the more commonly
used hand-held GPS, both in position computation and accuracy.
Whereas hand-held receivers used in a differential GPS mode rely
on the use of the GPS pseudocode to
resolve position, geodetic-quality receivers use phase measurements
of the of the two carrier phases in the GPS signal. The best possible
accuracy that can be expected from hand-held receivers in differential
GPS mode is + 1m in the horizontal plane, and upwards of + 10m in height, due to the geoid-ellipsoid separation.
The geoid-ellipsoid separation is the difference between the actual
height of a point as determined from a specific datum (usually
mean sea level), and the height from GPS measurements based on
the datum WGS84.
Accuracies
in the order of 1mm per kilometre of baseline length are achievable
(where a baseline is the vector between two GPS receiver stations).
However, geodetic-quality GPS requires considerably more field
time and post-processing time, and must be done by qualified surveyors.
Despite
time constraints, access problems, and the relative inexperience
of the field party, a very fair degree of accuracy was achieved,
with many locations being recorded at accuracies of + 0.03m
or less in the vertical plane. (A more detailed description of
this project is currently in
prep by Wakelin-King & Collier.) The local geoid-ellipsoid
separation was provided by the AUSLIG service Ausgeoid,
and was found to be accurate to a maximum error of 5mm over the
entire survey area.
As
part of the process some highly accurate bases were established
on pre-existing concrete surveyors’ markers. These markers were either unofficial, with no
pre-existing location data (which we named Homestead and Boundary
Beacons); or State Survey Markers with pre-existing height
data only, installed during the construction of the Silver City
Highway (numbers prefixed with SSM). Full coordinates or horizontal
coordinates were propagated onto these markers, which were then
used as reference points. The coordinates (in Geodetic Datum of
Australia ’94 and AHD) are presented here for use by other Fowlers
Gap researchers (Table 1). Homestead Beacon is between Cottage
5 and the Managers’ Cottage; Boundary Beacon is on the boundary
fence between Fowlers Gap Station and the Selection. (A beacon
is the boxy metal structure, mounted about 4m high on 3 or 4 strong
metal legs; under the beacon is the concreted marker with a metal
central point). The other concrete markers are along the Highway:
these are identifiable by SSM number, and some have beacons above
them. Information regarding these markers is available from the
Land Information Centre,
New South Wales
.
TABLE
1. Co-ordinates of Surveyed
markers (datum: GDA94 and AHD)
Name |
Easting |
Northing |
Height |
Homestead
Beacon |
567069.407 |
6560725.418 |
179.968 |
Boundary
Beacon |
582477.831 |
6570791.939 |
133.368 |
SSM30033 |
576089.119 |
6573239.430 |
141.744 |
SSM31900 |
568026.879 |
6562067.178 |
(available
from |
SSM31901 |
571504.111 |
6563437.561 |
LIC,
NSW) |
SSM3655 |
- |
- |
160.496 |
SSM3658 |
574487.333 |
6567509.764 |
149.328 |
SSM3659 |
572821.183 |
6564789.799 |
157.941 |
SSM3660 |
570513.118 |
6562440.630 |
167.692 |
SSM3661 |
568031.953 |
6561003.789 |
177.178 |
SSM3662 |
566651.418 |
6558407.577 |
198.567 |
SSM3665 |
561767.141 |
6546453.532 |
237.034 |
SSM3666 |
559991.830 |
6543696.012 |
264.721 |
SSM3667 |
- |
- |
242.336 |
SSM3668 |
- |
- |
256.168 |
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