Scientific Name
Common
Name
Conservation
status (WA)
Population
(no. of
individuals)
Season
Monitoring
Period
Acanthiza
robustirostris
Slaty-backed
Thornbill
none
resident
2008 - 2008
Anas gracilis
Grey Teal
none
0
–
28,312
unknown
1999 - 2003
Anas superciliosa
Pacific Black
Duck
none
0
–
63,560
unknown
1999 - 2003
Anhinga
novaehollandiae
Australian
Darter
none
0
–
1,474
unknown
1999 - 2003
Ardea pacifica
White-necked
Heron
none
0
–
2,148
resident
1999 - 2003
Ardeotis australis
Australian
Bustard
Priority 4 (WA)
resident
1998 - 2008
Aythya australis
Hardhead
none
0
–
76,746
resident
1999 - 2003
Burhinus grallarius
Bush
Stonecurlew
Priority 4 (WA)
resident
1998 - 2008
Chlidonias hybrida
Whiskered
Tern
none
0
–
19,601
unknown
1999 - 2003
Conopophila whitei
Grey
Honeyeater
none
resident
2008 - 2008
Cygnus atratus
Black Swan
none
0
–
17,535 i
resident
1999 - 2003
Dendrocygna
eytoni
Plumed
Whistling-duck
none
0
–
17,500
resident
1999 - 2003
Emblema pictum
Painted Firetail
none
resident
2008 - 2008
Eremiornis carteri
Spinifexbird
none
resident
2008 - 2008
Falco hypoleucos
Grey Falcon
Schedule 1 (WA)
resident
1998 - 2008
Himantopus
leucocephalus
White-headed
Stilt
none
0
–
24,837
unknown
1999 - 2003
Malacorhynchus
membranaceus
Pink-eared
Duck
none
0
–
11,157
unknown
1999 - 2003
Neopsephotus
bourkii
Bourke's Parrot
none
resident
2008 - 2008
Pezoporus
occidentalis
Night Parrot
Schedule 1 (WA)
18
unknown
2005 - 2005
Phalacrocorax
melanoleucos
Little Pied
Cormorant
none
0
–
5,991
unknown
1999 - 2003
Phalacrocorax
sulcirostris
Little Black
Cormorant
none
0
–
27,630
unknown
1999 - 2003
Poliocephalus
poliocephalus
Hoary-headed
Grebe
none
0
–
12,673
unknown
1999 - 2003
Threskiornis
spinicollis
Straw-necked
Ibis
none
0
–
16,947
unknown
1999 - 2003
4.2.4
Surface water catchments
Catchment areas contributing flows to the Marsh include (Map 4-01):
Ecohydrological Conceptualisation of the Fortescue Marsh Region
Status: Final
September 2015
Project No.: 83501069
Page 92
Our ref: FM-EcoConcept_v8.docx
downstream portions of the Fortescue River catchment. The majority of this catchment
extends
beyond the study area;
downstream portions of the Weeli Wolli Creek catchment, on the alluvial fan of this creek system.
The majority of this catchment extends beyond the study area;
Koodaideri Creek;
Chuckalong Creek, located between the Weeli Wolli Creek to the west and
Mindy Mindy Creek to
the east;
Coondiner
Creek and Mindy Mindy Creek;
BHP Billiton Iron
Ore Roy Hill East;
Goman/
Sandy Creek;
Christmas Creek;
Kulbee Creek; and
Kulkinbah Creek.
The Marsh itself consists of two basin areas (east and west) s eparated by a slightly more elevated
divide.
For each of these catchments, the relative contribution of different EHUs to the catchment area provides
an indication of surface water processes (source, transfer and receiving) operating within the catchment
(Map 4-01). This also provides a basis for comparing different catchments. For example, the Weeli Wolli
Alluvial Fan sub-catchment to the south of the Marsh comprises mostly lowland sandplains, with gently
undulating surfaces, significant infiltration losses and low surface water runoff. In contrast, the
Goman/Sandy Creek sub-catchment to the north of the Marsh includes a combination of upland source
and transitional areas with short flowpaths and high runoff, and lowland alluvial plains with higher
infiltration and lower surface runoff.
Each of the study area catchments are described in more detail as follows.
Catchments contributing to the eastern fringe of the Fortescue Marsh
A relatively small portion of the Fortescue River catchment, being 2,152 km
2
of the total catchment area
of 16,281 km
2
, lies within the study area to the east of the Marsh (Map 4-01). This area can be
partitioned into two distinct sub-areas, north and south of the Fortescue River respectively. The northern
sub-area contains areas of EHUs 1 and 2 - upland source areas comprising hills and dissected slopes
and plains. Surface water runoff from these areas is directed via dendritic drainage networks through
short flow paths that terminate in the Fortescue River. The southern sub-area consists of lowland alluvial
plains and sandplains (EHUs 5 and 6), which constitute part of the Fortescue River alluvial fan. These
EHUs are associated with poorly defined drainage patterns, high infiltration rates and minimal runoff;
although, some local scale surface water redistribution may occur. The Fortescue River including its
associated floodplain is classified as a lowland major channel system (EHU 8).
Catchments contributing to the southern fringe of the Fortescue Marsh
Catchments that lie on the southern fringe of the Marsh include the Koodaideri Creek, Weeli Wolli
Alluvial Fan, Chuckalong and Mindy Mindy/Coondiner Creek sub-catchments. These sub-catchments
drain from the Hamersley Range and extend across the wide, flat plains between the base of the
Hamersley Range and the Marsh. The Chuckalong catchment is a small catchment between the Weeli
Wolli Alluvial Fan catchment and the Mindy Mindy / Coondiner Creek catchment. Examination of the 5 m
DEM revealed that the Mindy Mindy Creek catchment is a sub-catchment of the Coondiner Creek
catchment, with Mindy Mindy Creek flowing into the Coondiner Creek downstream of Coondiner Pool.
Each of these catchments includes upland source areas of the Hamersley Range (EHUs 1 and 2) in
association with upland drainage floors and channel networks (EHUs 3 and 4); however the proportional
contribution of these units varies considerably between the catchments .
18
Also a listed species under the Commonwealth
Environment Protection and Biodiversity Conservation
Act 1999 (EPBC Act)
Ecohydrological Conceptualisation of the Fortescue Marsh Region
Status: Final
September 2015
Project No.: 83501069
Page 93
Our ref: FM-EcoConcept_v8.docx
Upon exiting the Hamersley Range, channel flows are dissipated across the lowland plains. Drainage
through these areas can be complex and consists of low-energy channels, channel breakouts and
depressions. Areas of sheetflow may also occur as dictated by surface types and gradients. Within the
lowland sandplains, drainage is poorly organised and infiltration rates are high. Along the fringes of the
marsh, the calcrete plains (EHU 7) have numerous localised drainage termini which can collect runoff, in
addition to drainages extending into the Marsh.
One of the most significant features to the south of the Marsh is t he Weeli Wolli alluvial fan (Map 4-01).
The distribution of flow between the channels within the alluvial fan area varies with the intensity of the
event. For example, during low flow events, flow will be confined exclusively to the main Weeli Wolli
Creek channel; whereas, during large events the flow within the main channel would only represent a
small proportion of the total flow across the alluvial fan.
Surface water runoff from the Mindy Mindy / Coondiner Creek sub-catchment, with an area of 3,205 km
2
,
flows in a north-easterly direction from the Hamersley Range into the Fortescue Valley. Coondiner
Creek flows through Eagle Rock Pool and Eagle Rock Falls in the upper reaches of the catchment, and
Coondiner Pool at the base of the creek system (Map 3-01). Coondiner Pool occupies an area of
approximately 0.09 km² and is classified as a shallow, semi-permanent claypan area/wetland. It is
underlain by low permeability, fine to medium-grained alluvium.
The Wanna Munna sub-catchment lies to the southwest of Coondiner Creek sub-catchment, outside the
study area. It is a relatively small catchment with an area of 502 km
2
and is bound by the Fortescue
River, Weeli Wolli Creek and Coondiner Creek sub-catchments. The Wanna Munna sub-catchment is
believed to respond primarily as an internally draining catchment during minor and average rainfall
events. However, following significant rainfall events the internal capacity of this catchment may be
exceeded with flows spilling over into Coondiner Creek. It is not known whether there is any significant
groundwater outflow from the Wanna Munna area into the study area.
Catchments contributing to northern fringes of the Fortescue Marsh
Drainage from the Chichester Range flows towards the Marsh via a series of floodplains, all uvial fans
and incised ephemeral creeks. These drainage features extend along the northern edge of the Marsh,
between 5 and 10 km from the base of the Chichester Range and sloping at around 0.3%.
Catchments lying to the north of the Marsh include the BHP Billiton Iron Ore Roy Hill East, Goman/
Sandy Creek, Christmas Creek, Kulbee Creek and Kulkinbah Creek c atchments (Map 4-01). These
catchments include a relatively even distribution of upland source areas (EHU 1 and 2 within the
Chichester Range) and lowland alluvial plains (EHU 6).
The upland areas drain into a series of relatively well-defined, parallel drainage channels. Moving further
south, the topography becomes flat and the drainages become narrower and more divergent. A number
of drainages penetrate into the Marsh, where they further distribute into splay channels and marsh
playas. Areas of sheetflow may occur in the interdrainage zones. In comparison with the catchments
located on the southern fringes of the marsh, flow distances from the upland to lowland areas on the
northern fringes of the Marsh are shorter and cross a narrower alluvial plain.
In some locations the drainages from these northern catchments feed into semi -permanent waterbodies
on the fringes of the Marsh, possibly associated with channel remnants and scours. These waterbodies
are referred to as Yintas and have cultural significance to Traditional Owners.
Fortescue Marsh Basin
The Marsh (EHU 9) is the terminus for all surrounding catchments. Runoff from the surrounding
catchments is influenced by surface detention, vegetation uptake, seepage and other removal processes
before reaching the Marsh basin.
Examination of the 5 m DEM suggests that flood waters can pond up to 8 m in depth in the lowest
elevation portions of the marsh following significant flood events. Water stored in the Marsh will slowly
dissipate via seepage and evaporation. As these dissipation processes progress, the extent of the
Marsh waterbody decreases and separates into a series of pools as controlled by basin topography until
the surface completely dries. During the evaporation process, surface water salinity increases and
traces of precipitated salt can be seen as floodwaters recede. During the seepage process, a proportion
of the increasingly saline waterbody percolates into the deep, valley floor alluvium.
Based on comparison between Landsat and surface topographic data, flood peak elevations of up to
407 m AHD have occurred in the Marsh area in the past several decades. Spillover from the Marsh
Ecohydrological Conceptualisation of the Fortescue Marsh Region
Status: Final
September 2015
Project No.: 83501069
Page 94
Our ref: FM-EcoConcept_v8.docx
beyond the Goodiadarrie Hills requires Marsh flood elevations in excess of 412 m AHD, suggesting that
this is a very rare event under the prevailing climate regime.
Examination of the 5 m DEM, together with aerial photographs, shows that the Marsh can be partitioned
into two internal catchment areas (Figure 4-7). These eastern and western basins interconnect during
and following large flood events and wet periods, but may remain disconnected with lower inflows. The
eastern basin is likely to spillover into the western basin at a level of around 406 m AHD. While the east-
west divide is evident from the 5 m DEM and satellite imagery of flood inundation areas, field
investigation and groundtruthing would be required to understand the process and explaination for
formation of the divide.
Satellite imagery of the Marsh (Figure 4-7 top frame) clearly illustrates this east-west divide, showing
inundation of the eastern basin whilst the western basin remains dry. This situation was likely due to
inflow from the upper Fortescue River catchment, following a localised rainfall event. The bottom frame
in Figure 4-7 shows the Marsh basin elevations based on the 5 m DEM, with lower elevations to the east
of the divide.
Ecohydrological Conceptualisation of the Fortescue Marsh Region
Status: Final
September 2015
Project No.: 83501069
Page 95
Our ref: FM-EcoConcept_v8.docx
Figure 4-7: Fortescue Marsh internal catchment delineation as indicated by: inundulation of the west catchment only in early 2012 (Top) and by elevation differences between the east and west basins (Bottom)
Ecohydrological Conceptualisation of the Fortescue Marsh Region
Status: Final
September 2015
Project No.: 83501069
Page 96
Our ref: FM-EcoConcept_v8.docx
4.2.5
Flood regime
Surface water expression is intermittent across the majority of the Marsh. Flooding of the Marsh
corresponds with episodic surface flow events.
Little data are available to quantify the flood regime of the Marsh. Flooding of the Marsh results from
direct rainfall, runoff from the surrounding catchments and inflow from the Upper Fortescue River and
Weeli Wolli Creek. Large surface water inflows to the Marsh are generally associated with large-scale
cyclonic events in the summer months, with a mean recurrence interval of about five to seven years
(DEC 2009).
Historical flooding patterns of the Marsh can be inferred from Landsat imagery. The combination of
Landsat imagery and high resolution DEM information can be used to improve the estimates of flooding
depths and extents. A baseline flooding history dataset has been generated by UWA PhD candidate
Alex Rouillard based on a review of historic Landsat images, but is yet to be published. This data would
be useful to validate outputs from the conceptual water balance model (Section 4.2.6), which suggested
a maximum (simulated) flooding extent of just more than 50% of the total Marsh area, and occurred only
once over a 27 year simulation period (further detail provided in Section 4.2.7).
Rainfall measured at the BOM Wittenoom rainfall gauge (BOM station number 5026) shows a largely
drying cycle (Figure 4-8) for most of the period from 1950 to the mid 1990s. This period is followed by a
wet period to the early 2000s, with clear indications of a drying period since 2001/02.
A conceptual depiction of the dynamics of flooding and drying scenarios observed in the Marsh over the
past three decades is shown in Figure 4-8. During the drought period from 1980 to around 1993, surface
water inflows to the Marsh were well below the longe term average, with low volumes of water captured
in the Marsh resulting in the Marsh being dry for extended periods. The Marsh acts as a groundwater
sink although the net groundwater contribution to the Marsh is minimal, owing to the removal of shallow
groundwater by evapotranspiration.
A much wetter period followed between 1999 and 2002, with a number of cyclones resulting in high
inflows into the Marsh and extended periods of ponding. This wetter phase facilitated groundwater
recharge and rise of the watertable. The nature of groundwater flow during mounding events is still
radial with respect to the Marsh basin, however the flow directions may be reversed (i.e. away from the
Marsh) for short periods until the groundwater system re-equilibrates.
The current period (post 2002) has seen a reduction in rainfall and runoff into the Marsh. The reduction
in inflows and ponding events has contributed to a general drying trend compared to the 1999 to 2002
wet period.
Outputs from the Marsh conceptual water balance model (Fig ure 4.13 and Figure 4.14) support the
contention that the Marsh experiences long term (interannual to decadal) drying and wetting cycles in
response to climatic conditions.
Ecohydrological Conceptualisation of the Fortescue Marsh Region
Status: Final
September 2015
Project No.: 83501069
Page 97
Our ref: FM-EcoConcept_v8.docx
Figure 4-8: Conceptual flooding and drying dynamics of the Fortescue Marsh groundwater with
rainfall cumulative deviation plot (BOM Wittenoom gauge)
Ecohydrological Conceptualisation of the Fortescue Marsh Region
Status: Final
September 2015
Project No.: 83501069
Page 98
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4.2.6
Hydrogeological setting
As detailed in Section 2, the Fortescue Valley is underlain by a flat-lying, complex sequence of
Quaternary and Tertiary alluvial, colluvial and lacustrine sediments. The saturated thickness of
sediments beneath the Marsh which overlie sedimentary rocks of the Wittenoom Formation is on
average 40 m (can be deeper, up to 70 m bgl, at places).
Hydrostratigraphy
The M
arsh’s aquifer
system (Figure 4-9) is associated with the following general hydrostratigraphic
sequence:
Alluvial and colluvial deposits, consisting mainly of fine grained material but with occasional
courser grained components such as those associated with outwash fans. The permeability of
the alluvium is reported to be in the order of 0.1 to 1 m /day, with coarser material exhibiting
higher permeability (FMG 2005a). The alluvium is the product of complex formation proce sses
and is likely to be highly variable physically and with respect to its hydraulic properties. In places
the Marsh bed includes shallow hardpans with very low permeability.
Tertiary Detritals (TD3 unit). A mix of complex lacustrine deposits, with textural variations from
sandy silt to a silty clay, generally texturally finest at the Marsh, with very low permeability (less
than 0.1 to 0.01 m/day), effectively an aquitard. Pisolitic gravel may be present in places at the
base of the TD3 unit forming localised aquifers.
Calcrete layers associated with ancient watertable levels. Although referred to as calcrete this
unit may contain significant silcrete and ferricrete horizons as the new drilling work undertaken in
2013 and 2014 by UWA shows that this unit underwent further significant silicification or iron
enrichment at places. In the Mount Lewin area, the hydraulic conductivity of the calcrete unit has
been determined to be in the range of 3 m/day to 20 m/day, with an average of approximately 10
m/day (Aquaterra, 2005c). The permeability of the calcrete in the area north of the Marsh is
significantly higher, FMG (2010) reporting values over 100 m/day. There may be other
calcretisation horizons within the Fortescue Valley, as it is not clear whether the calcr ete
outcrops to the south of the Fortescue Marsh belong to Oakover Formation. The recent UWA
work confirms that in parts of the Marsh, particularly along the southern perimeter of the Marsh
and further south of that perimeter, outcropping calcrete extends to a depth of approximately 16
to 25 m bgl. Calcrete is an important part of the regional aquifer under the Fortescue Marsh.
Brecciated siliceous caprock has also been identified as a potential aquifer within the
alluvial/colluvial deposits in the Fortescue Valley area (MWH 2009).
On the northern flanks of the Marsh, the mineralised Marra Mamba Formation (a member of the
Hamersley Group) dips and intersects the alluvium and Wittenoom Formation. The permeability
of the Marra Mamba Formation is reported to be in the order of 3 m/day (Aquaterra 2005c).
The Wittenoom Formation dolomite at depth under the Marsh. Weathered sections of the
Wittenoom dolomite tend to have relatively high transmissivities (in the order of 20 m /day or
more) due to the karstification (MWH 2009).
Beneath the Marsh the aquifer system hosts saline to hypersaline (in the order of TDS 10,000 to 75,000
mg/L) water and the deeper aquifers are saturated with hypersaline water (in the order of TDS 75,000 to
160,000 mg/L) (FMG 2005a; FMG 2009a). The hypersalinity is a consequence of the downward density-
driven migration of salt due to the increased density of the solution.
Ecohydrological Conceptualisation of the Fortescue Marsh Region
Status: Final
September 2015
Project No.: 83501069
Page 99
Our ref: FM-EcoConcept_v8.docx
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