Environmental Water Requirements of Aldinga Scrub, Blue ... · PDF fileEnvironmental Water Requirements of Aldinga Scrub, Blue Lagoon and the Washpool The City of Onkaparinga and The

Environmental Water Requirementsof Aldinga Scrub, Blue Lagoon andthe Washpool

The City of Onkaparinga and The OnkaparingaCatchment Water Management BoardPO Box 1NOARLUNGA CENTRE SA 5168

24 January 2003

REPORT REF. AE002 – R009B

Executive Summary

Introduction

Ecological Associates Pty Ltd was engaged by the Onkaparinga Catchment Water Management Board

and the City of Onkaparinga to assess the environmental water requirements of the Washpool, BlueLagoon and the Aldinga Scrub.

Background

The Aldinga Scrub, Washpool and Blue Lagoon are among the most important coastal woodland andwetland ecosystems remaining in the Adelaide metropolitan region. These ecosystems support plantassociations and fauna of conservation significance, including rare and threatened species and migratorybirds protected by international treaties. The wetlands and springs of the area have considerable

Aboriginal heritage value. These ecosystems have been degraded through by past drainage works andthey continue to be threatened.

The City of Onkaparinga is currently planning future land use and stormwater management in the SilverSands catchment. Rehabilitation and development of the stormwater system presents an opportunity toamend the surface and groundwater environment of the Aldinga Scrub, Washpool and Blue Lagoon.

Aldinga Scrub

The Aldinga Scrub is a complex of woodland and wetland habitats with a high plant diversity. Theecosystem is formed in freely-draining sands which overlie a low-permeability clay. A perched water

table develops in these sands, supporting the growth of Red Gum, Pink Gum and wetland plants andanimals. The water table creates freshwater wetland habitats in the north-east and saline waterholes nearthe coast.

The perched water table is believed to have been depleted. Surface water flows to Aldinga Scrub fromnorth of Aldinga Beach Road have been diverted to the sea. The shallow Quaternary sediments to the east

have been drained by channels near Main South Road, reducing flooding near the Scrub and increasinggroundwater flow away from the Scrub.

It is believed that the depleted water table now provides less reliable wetland habitat, resulting in fewerwater bird breeding opportunities, poorer tree health and lower plant diversity. The declining trend inecosystem health is believed to be ongoing.

The proposed management objective for Aldinga Scrub is therefore:

"to provide a suitable surface water and groundwater regime to maintain the health of groundwaterdependent woodland vegetation and to restore the former water regimes of wetlands and waterholes."

Blue Lagoon

Blue Lagoon is a small enclosed depression south of Norman Road. Blue Lagoon supports a LignumShrubland, which is sustained by seasonally waterlogged conditions. Blue Lagoon is rarely flooded and

Executive Summary

does not provide reliable feeding or hunting opportunities for waterbirds. Located near houses and

Norman Road, it is subject to ongoing disturbance. The site is isolated from other natural habitats byNorman Road or developed land.

Blue Lagoon bears little resemblance to the wetland described by historical reports. The wetlandoriginally supported duck populations of 400 to 500 birds, was 2 m deep and permanently flooded. BlueLagoon would have provided a complimentary deep water environment that was not present in Aldinga

Scrub or the Washpool. The lagoon would also have provided a continuous linkage between theseecosystems. They are now each isolated by farmland.

The proposed management objectives for Blue Lagoon are therefore:

"to preserve the remnant of Blue Lagoon as an isolated Lignum Shrubland; and

to recreate the deep water habitat formerly provided by Blue Lagoon and to restore the continuoushabitat linkage between Aldinga Scrub and the Washpool in a new constructed wetland, in the vicinity ofthe original Blue Lagoon site on modified farming land."

The Washpool

The Washpool is a low-lying, shallow coastal marsh that receives stormwater from the Silver Sandscatchment. The Washpool provides an important water bird habitat, particularly for wading species. Italso supports several rare and threatened plants.

The Washpool has been significantly altered from its original structure over the past 100 years, from a

semi-permanent freshwater wetland to a shallow, temporary coastal marsh. However, it now has newsignificant conservation values in its own right which should be preserved. If required, the habitatsformerly found in the Washpool could be created nearby in a constructed wetland, possibly near BlueLagoon.

The proposed management objectives for the Washpool are therefore:

"to maintain the new environment of the Washpool as a wading bird habitat; and

to promote waterbird breeding, waterbird carrying capacity and plant and animal diversity by increasingthe extent and duration of flooding in the wading bird habitat."

Recommendations

Restoration of Aldinga Scrub Perched Aquifer

It is proposed that a wetland is constructed on Hart Road north of Aldinga Scrub to recharge the perchedaquifer and provide surface flooding to wetland areas. The wetland would be designed to leak to theperched aquifer beneath the Scrub.

Executive Summary

Control of Flow Peaks in the Washpool

Flows to the Washpool occur in shorter, larger peaks than previously, resulting in intermittent flooding, apremature end to flooding each spring and lost opportunities for waterbirds to breed.

The detention of stormwater within the catchment could assist in damping stormwater peaks and

prolonging flooding. Stormwater detention basins could be designed to capture and slowly release stormflows downstream and may also have an engineering benefit in controlling flooding.

Restoration of Blue Lagoon

The permanent deep water wetland habitat originally provided by Blue Lagoon could be created throughthe construction of a stormwater wetland to the east of the remnant basin near Norman Road. The wetlandwould receive inflows from the drain below Norman Road and detain them before release to theWashpool. The constructed wetland would link the Washpool and Aldinga Scrub habitats.

Increase Flood Duration and Extent of the Washpool

The carrying capacity for waterbirds and plant diversity at the Washpool could be increased by increasingthe inundated area. This could be achieved by raising the sill at the outlet to the sea or by removingrecently deposited fill and sediment from the wetland edges.

Further Investigations

It is recommended that a detailed and calibrated catchment flow model is developed to predict monthlyinflows to system for a range of event probabilities. The model is required to provide advice on:

• hydrological parameters for the design of restored Blue Lagoon (size, depth, extent, flood duration);and

• scope to reduce and prolong flow peaks to the Washpool through detention structures in thecatchment, a wetland at Hart Road, a restored Blue Lagoon, a raised sill and any combination ofthese.

This will involve further assessment in the design phase of the stormwater system.

It is recommended that a topographic survey is undertaken of the Washpool including surrounding floodprone land, enclosing banks and the outlet sill.

Contents

i

1 Introduction --------------------------------------------------------------------------------------- 1-1

1.1 Introduction 1-11.2 Project Context 1-11.3 Scope of Work 1-1

2 Background ---------------------------------------------------------------------------------------- 2-1

2.1 Study Area 2-12.2 Drainage 2-12.3 Aboriginal Cultural Heritage 2-3

3 Hydrogeology -------------------------------------------------------------------------------------- 3-1

3.1 Topography 3-13.2 Geology 3-13.3 Hydrogeology 3-13.4 Climate and Groundwater Hydrographs 3-43.5 Interference With Natural Groundwater Conditions 3-4

4 Aldinga Scrub-------------------------------------------------------------------------------------- 4-1

4.1 Ecosystem Structure and Water Dependence 4-14.2 Water Requirements 4-24.3 Change in Water Regime 4-34.4 Rehabilitation and Protection 4-4

5 Blue Lagoon---------------------------------------------------------------------------------------- 5-1

5.1 Ecosystem Structure and Water Dependence 5-15.2 Water Requirements 5-15.3 Change in Water Regime 5-15.4 Rehabilitation and Protection 5-2

6 The Washpool ------------------------------------------------------------------------------------- 6-3

6.1 Conservation Significance 6-36.2 Ecosystem Structure 6-36.3 Water Regime 6-46.4 Waterbirds 6-66.5 Water Requirements 6-96.6 Changes in Water Regime 6-126.7 Rehabilitation and Protection 6-14

7 Recommendations -------------------------------------------------------------------------------- 7-1

7.1 Conclusions and Management Objectives 7-17.2 Recommendations 7-2

8 References----------------------------------------------------------------------------------------- 8-1

Tables, Figures & Appendices

ii

Tables

Table 1 Water requirements of Aldinga ScrubTable 2 Water requirements of waterbirds at the WashpoolTable 3 Water requirements of the WashpoolTable 4 Summary of interpreted hydrological impacts on ecosystems

Figures

Figure 1 Aldinga Scrub and Washpool Lagoon Locality PlanFigure 2 Aldinga Scrub, The Washpool and Blue LagoonFigure 3 Interpreted Perched Aquifer Groundwater Levels 25-6-02Figure 4 Geological SettingFigure 5 Elevation of the Upper Surface of Hindmarsh ClayFigure 6 Interpreted Depth to Water Perched Water Table Aquifer (m) 25-6-02Figure 7 Interpreted Perched Aquifer Salinity (mg/L) April 2002Figure 8 Interpreted Port Willunga Formation Aquifer Groundwater Levels 25-6-02Figure 9 Interpreted Port Willunga Formation Salinity April (mg/L) 2002Figure 10 Interpreted Thickness of Hindmarsh Clay (m)Figure 11 Vegetation Communities of the Washpool and Blue Lagoon

Appendices

Appendix A Groundwater Monitoring DataAppendix B Climate DataAppendix C Species Referred to in Text

Introduction

1-1

1 Introduction

1.1 Introduction

Ecological Associates Pty Ltd was engaged by the Onkaparinga Catchment Water Management Board

and the City of Onkaparinga to assess the environmental water requirements of the Washpool Lagoonwetland system and the Aldinga Scrub.

Ecological Associates undertook this project in association with Resource and EnvironmentalManagement Pty Ltd and Graham Carpenter, Avian Ecologist.

1.2 Project Context

The Aldinga Scrub, Washpool and Blue Lagoon are among the most important coastal woodland andwetland ecosystems remaining in the Adelaide metropolitan region. Almost all coastal woodlands havebeen cleared and developed, and all major coastal wetlands have been drained. These ecosystems

support plant associations and fauna of conservation significance, including rare and threatenedspecies and migratory birds protected by international treaties. The wetlands and springs of the areahave considerable Aboriginal heritage value.

The ecological character of these ecosystems is closely dependent on their local surface andgroundwater environment. Previous studies have identified hydrological threats to the ecosystemsassociated with hydrological changes in the Silver Sands catchment and locally within the sites.

Hydrological change has been considerable over the past 100 years and has included the diversion offlows, channelisation of watercourses, changes in land use and urbanisation.

The City of Onkaparinga is currently planning future land use and stormwater management in theSilver Sands catchment. Rehabilitation and development of the stormwater system presents anopportunity to amend the surface and groundwater environment of the Aldinga Scrub, Washpool and

Blue Lagoon. It is possible, through sensitive planning, to mitigate existing ecological stresses and torestore degraded elements of the ecosystems.

This project was commissioned to characterise the role of surface and groundwater in the function ofthe ecosystems. The project assesses the water requirements of the ecosystems and makesrecommendations for water management to maintain and enhance ecological character.

1.3 Scope of Work

The scope of work for this project was to:

• Collate and review existing ecological, hydrological and hydrogeological data relating togroundwater and surface water dependent ecosystems;

• Review the scope to enhance and restore the site in terms of availability of land, water andacceptable impacts on adjacent land uses;

Introduction

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• Characterise the ecosystem in terms of dependence on surface and groundwater, both to sustain thecurrent ecosystem or to enhance the ecosystem to a less disturbed state;

• In association with hydrologists from the City of Onkaparinga, characterise the natural and currentinflows to the area;

• Establish a conceptual model of the groundwater system to estimate the influence of surfaceinflows on the groundwater environment on which the ecosystems depend;

• Categorise surface water inflows to the system in a range of flow bands according to key groups ofenvironmental water requirements; and

• Identify the priority of water requirements considering:

- maintenance of the overall function / existence of the ecosystem;

- protection of the national, South Australian and regional conservation values; and

- enhancement of the ecosystem.

Background

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2 Background

2.1 Study Area

The Aldinga Scrub, Blue Lagoon and Washpool are located approximately 41 km south of Adelaide.The area lies within the Silver Sands catchment, in the south-west part of the Willunga Basin.

Figure 1 presents the location of Aldinga Scrub, Blue Lagoon and the Washpool.

The Aldinga Scrub Conservation Park comprises 38.2 ha of Pink Gum, Mallee Box and wetland

vegetation. The scrub extends from the beach inland approximately 2 km and lies on the gently sloping(1:200) northern face of the Silver Sands catchment between Norman and Hart Roads, behind thecoastal dunes. In contrast to the surrounding landscape, the Scrub was not cleared in the early years ofsettlement, partly due to the poor agricultural potential of the sandy soils on which it lies and partly

due to difficulties in accessing the flood-prone area. It is therefore an important representative remnantof the former vegetation of the area and coastal ecosystems in particular.

Blue Lagoon is a small (approximately 1 ha) enclosed wetland basin located south of Aldinga Scrub,south of Norman Road and behind the coastal dunes. Originally a deep, semi-permanent water body,the wetland has been reduced in size and made drier through land reclamation and the diversion ofinflows to the Washpool.

The Washpool is a coastal marsh located south of Blue Lagoon and receives most of the stormwater

runoff generated in the Silver Sands catchment. The wetland is enclosed approximately by NormanRoad, Justs Road and Button Road. The Washpool comprises a flat basin surrounded by low dunesand ridges that is waterlogged and flooded annually. The Washpool drains to the sea and occasionallyreceives sea water inflows in storm tides.

2.2 Drainage

The Silver Sands Catchment is 3,320 ha in area and predominantly rural (Kinhill 1996). Urbandevelopments and remnant vegetation each make up approximately 5% of the catchment. The

catchment is bounded to the south and east by the steep and deeply incised Sellicks Hill Range atapproximately 300 m AHD and to the north by a low rise at approximately 30 m AHD in the vicinityof Quinliven Road and Biscay Road.

Prior to European Settlement the Aldinga and Sellicks Beach area was flood prone and difficult toaccess. Runoff generated in the Sellicks Hill Range discharged to the poorly drained, low relief plain.

Water flowed to the coast via sub-surface and sheet flow, creating widespread and regular floodingparticularly in the vicinity of South Road between Aldinga and Sellicks Hill. A system of lagoons andmarshland extended on the eastern and part of the northern sides of Aldinga Scrub such that Aldingacould only be accessed from the north-west for only 6 months of the year (Gardiner 1989).

Background

2-2

The plain has been drained extensively over the past 100 years to reclaim flooded land and to facilitateagricultural development. The overall objective of drainage has been to minimise the potential forwaterlogging in properties by collecting and transferring runoff to the sea as quickly as possible.

Aldinga Scrub is located on a local sandy rise of the coastal Semaphore Formation, 2 to 10 m abovethe surrounding landscape. It is situated down-slope of a small catchment area that originally extendedapproximately 2 km north to Quinliven Road at Port Willunga. Since the installation of a stormwater

network in Aldinga, the Scrub only receives runoff from half of this area, south of Aldinga BeachRoad. Stormwater from the developed area is now diverted to the sea.

The eastern part of the Scrub lies at 10 m AHD and was originally flooded by diffuse surface flowsfrom the plain north of Hahns Road. Water up to 1 m deep originally persisted in this area for at least 6months each year (Gardiner 1989). Water gradually drained south to Blue Lagoon and then to the

Washpool (Gardiner 1989). A deep drain along Main South Road, 500 m east of the Scrub, interceptsthese flows and has reduced flooding in Aldinga Scrub.

The area between Aldinga and Sellicks Hill near Main South Road was also originally subject toannual flooding and waterlogging. This area is also drained. A main drain collects water betweenRogers and Hahns Roads to the east of Aldinga Scrub. This drain meets the Main South Road drainsouth of Cox Road. A third drain is located to the east of the Washpool and collects water betweenButton and Rogers Roads.

Flows from these areas originally entered Blue Lagoon, south of Aldinga Scrub, and then flowed tothe Washpool. Blue Lagoon was originally 2 m deep and remained flooded for most of the year. Itsextent is not clear from available records, but is reported to have supported 400 to 500 ducks, and waspresumably more than 3 ha (Gardiner 1989). The drains now divert water directly to the Washpool,isolating Blue Lagoon from the catchment.

The Washpool originally received runoff from the range behind Sellicks Hill in the southern part ofthe Silver Sands catchment. Flow from this area was diverted directly to the sea early in the 20th

century when a gully formed adjacent to the current location of Sellicks Beach Road. Ploughing alongthe fence line destabilised the soils and runoff rapidly formed the deep gully that exists today(Gardiner 1989).

The absence of a well defined outlet to the sea at the Washpool contributed to flooding inland. The

dunes were initially much higher and permitted outflows only once or twice per year. The Washpoolwas flooded by up to several meters and in particularly big storms, boats could be launched from MainSouth Road, approximately 2 km inland (Nurton in litt. 1989 in Australian Cultural HeritageManagement 1999). The sill level was lowered in the 1930s and 1940s when the dunes were excavated

to provide construction material for the Myponga Reservoir (Gardiner 1989). The system is now rarelyflooded to more than 0.4 m.

In addition to removing surface water, the drains are also believed to have affected the water table. Nogroundwater records are available to describe change in the water table associated with drains.However, it has been reported that following construction in the 1940s and 1950s, they flowed

Background

2-3

continuously for several years (Nurton 1995). The drains may have intercepted and gradually de-watered a local perched aquifer over this period.

2.3 Aboriginal Cultural Heritage

The Aldinga area is part of the region occupied by the Kaurna people. In general, it is believed that theKaurna people occupied coastal areas in summer and retreated inland during winter. However, there isevidence suggesting that the Aldinga Scrub and Washpool ecosystems were unusual in that theysupported more permanent occupation (Wood 1996).

The area provided diverse and substantial food sources. Coastal fish, including salmon, mullet, tommy

ruff and mulloway were plentiful in spring. Shellfish, including oysters, limpets, pipis, mussels andcockles were available from the foreshore. Food plants present in Aldinga Scrub include Nardoo,Native Cranberries, White Currents, Pigface, Muntries, Quandong, Yams and other fruits, roots andtubers. The Aldinga Scrub, Blue Lagoon, the Washpool and surrounding Grey Box woodland also

provided hunting for vertebrate fauna, including kangaroos, birds and lizards (Australian CulturalHeritage Management 1999).

The Washpool is known to the Kaurna people as Wangkondanangko (Possum Place). The Washpoolprovided a semi-permanent water source that was used to cure and prepare skins. Skins were cured byrubbing with stones to make them loose and flexible and rubbing them with dust to absorb the fat(Australian Cultural Heritage Management 1999). Artefacts associated with hunting, food preparation

and skin curing have been found throughout the Washpool area (Campbell 1988; Australian CulturalHeritage Management 1999).

Permanent freshwater was available in the Aldinga area (Wood 1996). At least three springs werepresent in Aldinga Scrub prior to European occupation. Brackish, but drinkable, water could also beobtained by accessing shallow groundwater in Willunga Creek at Port Willunga (Tindale 1987). A

spring was believed to be located by Tindale in the south-west of the Washpool, but has been lostthrough various excavations and earthworks over the past 50 years. The cultural significance of thesesprings and other water sources on the Fleurieu Peninsula is evident in the Tjibulke dreaming trail.

Hydrogeology

3-1

3 Hydrogeology

3.1 Topography

The ground surface in the study area ranges between around 0 and 33 m AHD. Ground surface

elevation contours are presented on Figure 1. The more elevated parts of the study area occur near tothe coastline along the western portions, and to the north of the Scrub. Lower elevations occur along adrain that runs along the southeastern boundary of the Scrub toward Washpool Lagoon. TheWashpool Lagoon likely represents a window to the perched water table aquifer, whilst also receivingstormwater runoff from the general area of, and west of, the site.

Land inland of the Scrub and Washpool Lagoon has been fairly extensively drained by a network of

drains. Local drains and the position of the Aldinga Scrub in relation to Blue Lagoon and TheWashpool is presented in Figure 2.

3.2 Geology

The Washpool Lagoon and Aldinga Scrub are located within the Willunga Embayment, which wasformed during the early Tertiary and is bounded to the west by the Ochre Cove – Clarendon Fault, andto the east by the Willunga Fault. The faulted embayments were initially infilled by swamp and

stream sediments, and later by a series of transgressional and regressional marine sediments (Selbyand Lindsay, 1982). Today, the area of the Scrub is covered by aeolian dune sands.

The four shallowest geological units that occur in the study area are (from shallowest to deepest):

1. Semaphore Sand (Quaternary-aged), beneath the Scrub and south toward the Washpool;

2. Undifferentiated (Quaternary-aged) deposits, inland and south of the Scrub;

3. Hindmarsh Clay, or its equivalent (Quaternary-aged) to the north of the Scrub, and underlyingthe entire study area; and

4. Aldinga Member of the Port Willunga Formation (Tertiary-aged).

Figure 3 presents a plan showing the distribution of the geological units named above. The upper

surface of the Hindmarsh Clay dips from the northern (and possibly eastern) portions of the study areatoward the south, as shown by Figure 4.

3.3 Hydrogeology

Overview

The following describes the groundwater system that occurs beneath the study area. In addition to theSemaphore Sand perched water table aquifer, the Hindmarsh Clay aquitard and Port Willunga

Hydrogeology

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Formation aquifer are also discussed. This has been done to assess the level of interaction that mayexist between the shallow and deep aquifers.

Semaphore Sand (Quaternary Perched Water Table Aquifer)

In the lower lying southern portions of the study area, eg. near the former Blue Lagoon, a permanentperched water table is formed within the Semaphore Sand, over the Hindmarsh Clay aquitard. Basedon a groundwater level near the middle of the Washpool (greater than 3 m AHD – WLG133), it is

probable that the perched system maintains, to some degree, the Washpool. However, there areinsufficient groundwater level data to confirm this.

In the more elevated portions of the study area a seasonal perched water table aquifer is formed withinthe Semaphore Sand unit. This perched system is believed to be discontinuous over the site (Kinhill,1988). Groundwater data collected by DWLBC indicate this aquifer becomes dry over summer andautumn months (refer Appendix A).

Figure 5 shows a higher perched water table elevation beneath the northern part of the Scrub, which is

consistent with the interpreted northern extent of the unit and the highest elevation of the upper surfaceof the Hindmarsh Clay aquitard.

This aquifer receives direct rainfall recharge. In addition, there may be a tendency for surfacedrainage between Rowley and How Roads collect within the swale that occurs in that area, from whereit infiltrates to perch on the Hindmarsh Clay. Based upon interpreted elevation data for the top of theHindmarsh Clay (Figure 4) and interpreted water table contours (Figure 5), the Semaphore Sand

receives no throughflow from areas east of the site, although there are little data to the east to validatethis interpretation.

The sloping upper surface of the Hindmarsh Clay aquitard (Figure 4) means groundwater that percheson that unit will tend to flow west toward the coastline, south toward Washpool Lagoon and southeasttoward the Quaternary deposits, which may or may not be in good hydraulic connection with theSemaphore Sand. Figure 5 presents interpreted groundwater flow directions.

The reported seasonal nature of the perched system in the northern portion of the study area suggeststhe major groundwater discharge process is associated with evapotranspiration, or downward leakagethrough the Hindmarsh Clay to the deeper Port Willunga Formation.

Figure 6 presents a plan showing the interpreted depth to the perched water table aquifer. As shown,the perched water table is shallowest in the central portion of the Scrub and south toward WashpoolLagoon.

Figure 7 presents interpreted salinity (as TDS) contours for the perched water table aquifer. The plan

has been constructed based on a limited data set. The plan shows an increase in groundwater salinityfrom east to west, with the highest concentrations occurring beneath that area of the site where theperched water table is at its shallowest. This is consistent with a greater potential for evaporativeconcentration of salts occurring where groundwater is close to the surface.

Hydrogeology

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Undifferentiated Quaternary Deposits (Quaternary Perched Water TableAquifer)

Clarke and Graham (2002) suggest that a perched water table exists within the UndifferentiatedQuaternary deposits east of the study area. However, a review of the bore log for well WLG137

indicates the lithology at the depth at which groundwater has been gauged is consistent with theHindmarsh Clay.

Hindmarsh Clay Formation Aquitard

The Hindmarsh Clay Formation in the study area ranges up to 20 m thick and, due to a relatively lowhydraulic conductivity, is expected to restrict downward leakage from the perched water table aquiferto the deeper Port Willunga Formation aquifer. The available groundwater level data and lithological

logs suggest that the topographic surface of this unit (Figure 4) provides the greatest control over localgroundwater flow conditions, i.e. perched water table groundwaters drain toward the west and south-southeast.

The Hindmarsh Clay is by no means an homogeneous aquitard, with sand sequences interspersedwithin the formation (Selby and Lindsay, 1982) to form sub-aquifers. This is reflected in the bore logfor well WLG137. Comparison of the interpreted regional water table elevation in the general area of

WLG137 (Clarke and Graham, 2002) suggests a perched system exists within a clayey sand sequenceof the Hindmarsh Clay.

Port Willunga Formation Aquifer

Depending on location in the study area, the regional Port Willunga Formation aquifer can be eitherconfined or unconfined (Clarke and Graham, 2002). As the Hindmarsh Clay dips toward the southand the coastline, the Port Willunga Formation water table aquifer becomes confined. Figure 8

presents a plan showing interpreted groundwater elevation contours, and groundwater flow directions,for the Port Willunga Formation aquifer.

Away from the coast, the Port Willunga Formation aquifer is recharged in the immediate study area byleakage through the Hindmarsh Clay Formation, although the rate at which this occurs is expected tobe relatively slow. Groundwater elevation data for wells WLG127 and WLG131 indicate this may

also be the dominant process close to the coast as well. Rainfall directly recharges the Port WillungaFormation aquifer further inland, mainly along the Willunga Fault and in areas where the Formationoutcrops.

Interpreted salinity (as TDS) contours, presented as Figure 9, are generally coincident with interpretedgroundwater level contours presented in Figure 8. They show that salinity increases from around1,000 mg/L east of the Scrub to over 10,000 mg/L beneath the Scrub. There is insufficient

information at this stage interpret the apparent relationship between salinity and groundwaterelevations, but seawater intrusion could be one possible explanation.

Hydrogeology

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Figure 8 shows the primary discharge zone for the Port Willunga Formation aquifer (in the study area)is likely to be beneath the Scrub, and not beneath the Washpool. Comparison of the shape of theinterpreted groundwater contours of the deeper aquifer and the shallow system indicates the twoaquifers are probably not in good hydraulic connection. In fact, based on a limited data set (i.e.

groundwater levels gauged at the Semaphore Sand well WLG133, and the Port Willunga Formationwell WLG132), it is apparent that a relatively steep downward hydraulic gradient (0.25m/m) existsbetween the perched and deeper groundwater systems.

Further, comparison of groundwater level contours presented in Figures 3 and 7, shows that there is adownward hydraulic gradient between the shallow and deeper aquifers over the entire study area. Thearea to the south of Washpool Lagoon is a possible exception to this observation, although sufficient

data are not available to support this conjecture. However, data presented in Coffey Geosciences(2000) suggests that even in this area the gradient is downward.

3.4 Climate and Groundwater Hydrographs

Appendix B presents rainfall data for the Aldinga climate station (#23700). Average annual rainfall is501 mm, and average annual evaporation approximates 1,410 mm (source: Australian Bureau ofMeteorology). On average, most rainfall occurs between the months of April and October, althoughsome rainfall (around 20 mm/month) does occur between November and March.

With the exception of WLG128, groundwater hydrographs (appendix A) show groundwater level

response to (what is attributed to) climatic factors, with perched aquifer groundwater levels generallyrising by less than a metre between April and the end of June 2002.

The observed groundwater level rise in the Port Willunga Formation aquifer is unexpected, especiallyif the aquifer is truly confined by the Hindmarsh Clay aquitard. There are two possible causes for thisresponse:

• the Hindmarsh Clay forms a very leaky aquitard; or

• unaccounted for stresses to the Port Willunga Formation, eg. pumping.

Further monitoring data are required to assist in ascertaining factors involved in aquifer response toclimatic (and other) factors.

3.5 Interference With Natural Groundwater Conditions

Semaphore Sand Perched Water Table Aquifer

Only two data points (wells WLG131 and WLG133) exist to compare differences between SemaphoreSand groundwater levels reported for 1988 (when monitoring commenced) and today. There appear to

be no substantial differences between 1988 and 2002 perched water table levels measured at well

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WLG133. However, reported groundwater level data for well WLG131 suggest that the perched watertable at that location has declined by around 4 m between 1988 and 2002. Given the similarity oflocations for these two monitoring points, the inconsistency between 1988 and 2002 groundwaterlevels should be further investigated and verified.

It is expected that groundwater discharging toward the south of the Scrub always has discharged toWashpool and Blue Lagoons. However, it is possible that installation of shallow drains may have

interfered to some extent with local perched water table dynamics (in both the Quaternary deposits andHindmarsh Clay, and possibly the Semaphore Sand), by intercepting shallow groundwater that mayhave previously discharged southeast of the Scrub area. The effect will depend on the degree ofhydraulic connection between the Semaphore Sand and Quaternary deposits / Hindmarsh Clay. If the

installation of drains has meant that groundwater is intercepted, the intercepted waters will likely bedelivered to Washpool Lagoon over a much shorter timeframe than that which would have occurredprior to drain installation.

Further construction or deepening of drains in the farmed areas east of the Scrub could (further)interfere with the shallow groundwater system and, if allowed to occur closer to the boundary of thestudy area, could contribute to a reduction in shallow groundwater levels beneath the Scrub itself.

Prior to drain construction, Washpool Lagoon would have been maintained primarily by groundwater

discharging from the north, east and possibly south. Runoff following storm events, or after prolongedwinter rainfall would also be expected to have assisted in maintaining Washpool Lagoon.

Port Willunga Formation Aquifer

There are only limited historical data that are available for the Port Willunga Formation aquifer.However, the available data suggest that groundwater levels are typically lower (with only twoexceptions; WLG132 and WLG136) but with no discernable pattern in the observed differences, eg.

well WLG127 reports a groundwater level decline of around 1.3 m between 1988 and 2002, whilstWLG134 (across hydraulic gradient) reports relatively static conditions over the same time andWLG132 (down hydraulic gradient) reports around 0.4 m recovery. These differences may be theresult of groundwater abstractions, seasonal factors, tidal influences, or a combination of any of theseinfluences.

With the exception of wells WLG125 and WLG 127, groundwater level data for the study area(Appendix A) indicate that overall conditions in the Port Willunga Formation aquifer probably remainmuch the same as those occurring prior to development of the Aldinga area, or are not influencedgreatly by existing activities in the immediate study area. Time series salinity data are not availablefor review.

The greatest likely future impact to this aquifer will possibly be a decline in water quality as a result of

the effects of irrigated horticulture (the impacts of which will likely be mitigated by the HindmarshClay), or development in the major recharge zones for this aquifer, east of the Aldinga Scrub area. Sea

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water intrusion arising from over-pumping of the Port Willunga Formation aquifer may also impact onthe long-term integrity of the aquifer.

There is little potential for impacts to the Port Willunga Formation Aquifer to affect surfaceecosystems due to the interpreted poor hydraulic connection with shallow aquifers.

Groundwater Pumping

Based on the reported high salinity of groundwater in both the Semaphore Sand and Port WillungaFormation aquifers it is unlikely that groundwater pumping takes place in the immediate area of theScrub or Washpool Lagoon. However, pumping of “fresh” groundwater lenses that have formed

beneath the dune sands that run close to the coastline most likely does occur. This, in association withlower recharge rates arising due to urban development (principally due to sealing of the ground surfaceby buildings and roads), is likely to have had, and will continue to have, an adverse impact on springsthat arise from the dunes to feed wetlands and small lagoons (such as Blue Lagoon).

Pumping from the Port Willunga Formation aquifer, up-hydraulic gradient of the study area, takes

place to support irrigated horticulture as well as domestic and stock water supplies. It is also probablethat the Quaternary sediments east of the study site are pumped for domestic and stockwater supply.However, due to the perched and unconfined nature of the Semaphore Sand aquifer, the largethickness of the Hindmarsh Clay aquitard in the study area (Figure 10), and the unconfined nature of

the Port Willunga Formation aquifer to the east of the study area, it is unlikely that pumping east of thestudy area has had or will have any adverse impact on either Washpool Lagoon or the perched watertable aquifer.

Aldinga Scrub

4-1

4 Aldinga Scrub

4.1 Ecosystem Structure and Water Dependence

Overview

The ecological structure of Aldinga Scrub is controlled to a large degree by the soil and groundwater

environment. The predominant soil type is deep, well drained sands (the Semaphore Sand) underlainby clay (the Hindmarsh Clay). The dependence of the ecosystem on water is associated with theperched aquifer that creates waterlogged or flooded conditions over shallow or outcropping clay.

The location of Aldinga Scrub in relation to Blue Lagoon and the Washpool is presented in Figure 2.

Pink Gum Sand Scrub

The white, sandy loam characteristic of most of the Scrub area is dominated by Pink Gum, DroopingSheoak and Golden Wattle. Other tree species are present to a lesser degree and include Mallee Box,

Quandong and Bitter Quandong. Where the sands are deep there is little potential for waterlogging andthe understorey is dominated by heath species including Heath Tea-tree, Beard-heath, CommonFringe-myrtle and Sea Box and various Epacrids. This vegetation association is similar to other sandscrubs in the region including Hardy's Scrub and Manning Reserve near McLaren Vale (Kraehenbuehland Smith 1989).

Where the sand is shallow the soils are more prone to waterlogging. The Pink Gum overstorey persists

in this area, but the understorey changes from a dryland heath to a wet sand scrub. Kraehenbuehl andSmith (1989) report that the Pink Gums near the wetland areas are particularly large, possibly due tothe greater availability of soil water. The understorey is dominated by species that are tolerant ofintermittent waterlogging including Black Bristle-rush, Bare Twig-rush and Rushes.

Wetlands

Sand is largely absent in the north-eastern corner of the Scrub, where the clay outcrops to create a

flood-prone wetland environment. The eastern boundary of the Scrub was originally a linked series ofwetlands that extended from the area north of Hart Road to Blue Lagoon in the south. This area wasflooded annually for at least six months to a depth of more than 1 m (Gardiner 1989). The wetlandoriginally supported a Red Gum woodland with an understorey of Lignum and Pale Rush. Most of the

Red Gum have been killed by fire but some examples remain near Hart Road. Understorey speciesinclude Loose-flower Rush, Stiff Flat-sedge and Spiny Flat-sedge. Areas subject to regular inundationsupport Common Reed, Sea Club Rush and Nardoo (Kraehenbuehl and Smith 1989). The salinity ofthe perched aquifer increases towards the coast up to 10,000 mg/L, and the wetland species associatedwith shallow groundwater tend to be salt tolerant.

The wetland habitat in the scrub provides an important level of complexity and complimentary habitatto the more permanent wetlands at Blue Lagoon and the Washpool. The woodlands around the

Aldinga Scrub

4-2

wetland provide nesting and roosting habitat for birds that hunt and graze the Washpool includingWhite-faced Herons, Australian Wood Duck, Pacific Black Duck and Grey Teal (Ashton 2001). RedGum are particularly important in this role because other tree species in the Scrub, Pink Gum andMallee Box, do not provide large enough hollows for these birds.

Prior to drainage of the area, Aldinga Scrub, Blue Lagoon and the Washpool would have beenconnected. The complexity of habitats in this system would have supported a greater diversity of

wetland fauna including invertebrates and freshwater fish. The permanent water associated withshallow groundwater would have provided drought refuges for aquatic species.

Waterholes

Waterholes are isolated depressions in the sand of Aldinga Scrub that expose the water table perchedabove the Hindmarsh Clay. At least three springs were present in Aldinga Scrub prior to Europeanoccupation. Blackfellows Waterhole was permanent, located in the south just east of Parrot Road. This

waterhole was covered by sand drift and lost in 1967 (Gardiner 1989). Cliffs Waterhole is still presentbut usually dries up in summer. A groundwater well known as Rekarnung is also present in the coastaldunes (Wood 1996).

The salinity of the waterholes reflects the local groundwater conditions. Rekarnung, nearer the coast,is reported to be relatively saline and located in an area dominated by salt tolerant wetland plants such

as Sea Club-rush and Sea Rush (Kraehenbuehl and Smith 1989). Cliffs Waterhole, in the east of thescrub, supports freshwater species. Waterholes are likely to provide watering points for vertebratefauna including woodland birds, reptiles and mammals. As productive sites for insects, they may alsoprovide hunting sites for insectivorous birds and bats. Permanent waterholes will support frogbreeding throughout the year and will attract predatory water birds such as Darters.

4.2 Water Requirements

The water requirements of Aldinga Scrub are presented in Table 1. below. The ecosystem depends on

the perched aquifer to sustain the wet heath vegetation of the Pink Gum Sand Scrub, the wetlandvegetation of Cliffs Waterhole and the former wetlands in the east and the waterholes elsewhere in thesystem. The water table is 1 to 2 m below ground level throughout the scrub (Figure 6). The salinity ofthe perched aquifer varies from less than 5,000 mg/L in the east to more than 10,000 mg/L near thecoast (Figure 7).

The current levels of the perched aquifer appear to be inadequate to sustain the current ecosystemstructure. Vegetation dependent on waterlogging may currently be in a drought phase. The vegetationmay tolerate current dry conditions, but eventually die and be replaced by vegetation more suited todry conditions. Groundwater records collected in 1988 and 2002 do not reveal an ongoing depletion of

the water table and the aquifer may have reached a steady state. Change in the ecosystem is likely tolag behind groundwater change and continues to reflect past groundwater conditions.

Aldinga Scrub

4-3

Ecological change may not yet be irreversible. The provision of the water to sustain the currentecosystem will require additional water to that currently received to maintain a higher water table andto permit seasonal surface flooding near Cliffs Lagoon. The water requirements in Table 1 are basedon existing information. Detailed site investigations are required to plan more accurately suitablewater management targets.

Table 1. Water Requirements of Aldinga Scrub

Period Area Depth and Salinity Key Outcomes

January toMay

Cliffs Lagoon Waterlogged, lessthan 5,000 mg/L

• Resting stage for aquatic vegetation

• Resting stage and recruitment for RedGum and Lignum

June toDecember

Cliffs Lagoon Flooded to 1 m, lessthan 2,000 mg/L

• Growth of wetland plants

• Regeneration of Red Gum and Lignum

• Hunting habitat for waterbirds

• Breeding conditions for waterbirds

Annual Sea RushRushlands

Flooded to 0.5 m orwaterlogged, up to10,000 mg/L

• Sustain dense rushlands

• Perennial breeding habitat for frogs

• Hunting habitat for insectivorous birdsand bats

It is only possible to estimate possible water requirements for areas where water levels and salinitieshave previously been reported. These include Cliff's Lagoon and saline waterholes in the east of theScrub. As described above, Pink Gum and other phreatophytes surrounding these areas will also

depend on groundwater. However the groundwater conditions they require cannot be clearly describeddue to the limited historical groundwater data for the area. Since the waterholes reflect thegroundwater conditions of the perched aquifer, the provision of suitable flooding regimes in thewaterholes will also meet the requirements of the surrounding phreatophytic vegetation. However, a

more precise relationship should be developed with groundwater and vegetation monitoring, asdescribed in Section 7.

4.3 Change in Water Regime

There are no hydrological or hydrogeological records for Aldinga Scrub to describe change in waterregime over the past 100 years. Groundwater levels recorded in 1988 do not indicate ongoing changein the water table (Section 4). Change in water regime can only be interpreted from anecdotalobservations and analysis of land use change.

Flooding in Aldinga Scrub is now limited to within Cliffs Lagoon and other isolated depressions, and

occurs for a shorter period than previously. Observations that indicate the former water regime of thearea include:

• Cumbungi and Common Reed were reported as common in 1973 but later as rare (FieldNaturalists Society 1990);

Aldinga Scrub

4-4

• reports that the area near Cliff's Waterhole was originally so waterlogged it was only suitable formelon farming (Field Naturalists Society 1990); and

• Gardiner's (1989) report of annual flooding to 1 m for at least 6 months in the eastern part ofAldinga Scrub and that flooding extended 500 m north of Hart Road.

Interpreted groundwater contours indicate that the drains to the east and south of the Scrub have drawndown the water table beneath the Scrub (Figure 6). It is possible that by preventing flooding alongMain South Road east of the Scrub, the drains also reduce the potential for surface flooding in the

Scrub. The diversion of stormwater collected north of Aldinga Beach Road to the sea will also haveaffected the Scrub.

4.4 Rehabilitation and Protection

Objectives

The objectives for the protection of Aldinga Scrub should be to provide the flooding and waterloggingrequired to sustain the current ecosystem. The objectives for restoration would go further and attemptto restore the former extent and duration of flooding.

The key requirements for water are presented below. Proposals to provide water requirements arepresented in Section 7.

Groundwater Recharge

Aldinga Scrub would be enhanced by promoting recharge of the perched aquifer up-slope.

Stratigraphic data indicates that the upper surface of the Hindmarsh Clay slopes southwards from HartRoad, immediately north of the scrub. Groundwater recharged in this area would flow southwards andcould be designed to raise the water table in the Scrub.

Surface Flooding

The promotion of surface flooding in Cliffs Lagoon would need to balance the requirements of theenvironment and flooding risks to adjacent landholders. The release of stormwater at the north of theScrub, near Hart Road, could be designed to restore the former overland flows of this area.

Blue Lagoon

5-1

5 Blue Lagoon

5.1 Ecosystem Structure and Water Dependence

Blue Lagoon is a small enclosed depression, approximately 1 ha in area, located south of Norman

Road behind the coastal dunes (Figure 11). The invert of the depression is approximately 2 m belowthe surrounding landscape and lies in the clay of the Hindmarsh Clay. The wetland is bounded to thenorth by Norman Road and by houses to the west and south. The only open area lies to the east and isreclaimed land currently used for cropping.

Blue Lagoon is sustained principally by direct rainfall, but may receive some stormwater runoff fromthe built-up area to the east. Consequently the wetland rarely floods, but is seasonally waterlogged.

This water regime supports a dense Lignum shrubland with an understorey of Notched Sedge(Valimanesh 1999). The surrounding vegetation is dominated by exotic grassland weeds.

Blue Lagoon currently has little habitat value for fauna. It is rarely flooded and does not providereliable feeding or hunting opportunities for waterbirds. Located near houses and Norman Road, it issubject to ongoing disturbance. The site is isolated from other natural habitats by Norman Road ordeveloped land. When flooded, Blue Lagoon may support visiting waterfowl.


The current ecosystem reflects the current water regime and can be maintained without manipulation.

The basin is dominated by drought-tolerant Lignum with an understorey of Notched Sedge whichdepend on seasonal waterlogging but are intolerant of prolonged flooding (Roberts 2001). This siteprobably requires waterlogging and flooding to 0.3 m annually for 2 to 3 months. This ecosystemwould persist without surface water flooding for up to five years.

5.3 Change in Water Regime

Blue Lagoon bears little resemblance to the wetland described by historical reports. The wetland

originally supported duck populations of 400 to 500 birds and was 2 m deep. Receiving dischargefrom the flooded area near Main South Road and Aldinga Scrub, Blue Lagoon would have beenpermanently flooded. Blue Lagoon would have provided a complimentary deep water environmentthat was not present in Aldinga Scrub or the Washpool.

The ecosystem is not well described in available historical records, but can be interpreted from thewater regime. It is likely that permanent deep water areas were vegetated with submerged aquatic

plants such as Milfoil and Pondweed which provide grazing material for ducks. The submergedvegetation would have supported aquatic invertebrates and fish, which provide food for predatorywater birds. The fringes of Blue Lagoon would have been vegetated with emergent macrophytes suchas Sea Club-rush and River Club-rush which provide protection and nesting material for several

species of water bird including Grebes and Black-tailed Native-hen. Blue Lagoon would have

Blue Lagoon

5-2

provided a drought refuge for aquatic fauna that could opportunistically spread into the seasonallyflooded areas to the east.

The drain below Norman Road diverts almost all of the water that formerly flowed to Blue Lagoon tothe Washpool. The extent of the wetland may also have been reduced by earthworks to fill in andreclaim surrounding land.


No action is required provide water to sustain Blue Lagoon in its current state.

The site represents an important opportunity to restore semi-permanent deep water habitats that usedto occur in the area. The wetland could be restored by constructing a deep water wetland south ofNorman Road to collect and detain stormwater. The wetland would contribute to the habitat diversityof the area and would contribute to the water requirements of the Washpool by damping flood peaks.

Rehabilitation recommendations are presented in Section 7.

The Washpool

6-3

6 The Washpool

6.1 Conservation Significance

The Washpool preserves important characteristics of coastal wetlands that are priorities forconservation including:

• rare and threatened wetland plants;

• migratory wading birds protected by international treaties;

• threatened water birds protected by South Australian and Federal legislation; and

• threatened wetland plant associations.

The Washpool has a significantly different hydrology and ecology from the ecosystem that existedprior to the settlement and drainage of the Sellicks area. Aspects of the original system that have been

lost include deep water habitats, linkages to Blue Lagoon and persistent flooding in summer. The sizeof the wetland has also been reduced.

Management of the Washpool should first address the protection and enhancement of existingecological values associated with the coastal marsh. Restoration of former deep wetland habitat shouldbe undertaken on adjacent land.

6.2 Ecosystem Structure

The Washpool is a shallow coastal lagoon located behind the coastal dunes of Gulf St Vincent (Figure11). The wetland is approximately triangular in shape and covers 38.2 ha. Button Road, built up on

gravel above the wetland level by approximately one metre, passes through the wetland from JustsRoad to the coast. Approximately two thirds of the wetland area lies north of Button Road. Floodingpatterns suggest a culvert beneath Button Road connects the two areas

The Washpool receives inflows principally from the north and north-east. The Norman Road draincollects water from the east of Aldinga Scrub and bypasses Blue Lagoon to enter the Washpool at itsnorth-eastern corner. A second drain, which collects water from the east of the Washpool, passes under

Main South Road south of Norman Road and enters the Washpool at the same location. The drainsmeet at an inlet channel that flows south-easterly on the eastern boundary of the wetland. The inletchannel delivers low flows to the lowest part of the wetland, near Button Road. Due to its limitedcapacity however, larger flows spill along the channel's length into the wetland basin.

A minor drain along Button Road contributes water from a smaller catchment to the east. A fourth

drain enters the southern corner of the system and contributes storm water collected from the newhousing development at Sellicks Beach.

The Washpool generally floods to a maximum depth of 400 mm. Water exits the system via an outletchannel to the sea which passes through the dunes just north of Button Road. A weir has been

The Washpool

6-4

constructed on the channel to reduce tidal inflow and to help retain fresh water in the wetland. Seawater occasionally enters the system during storms and high tides.

Due to its shallow depth, the Washpool has a low capacity to retain water. The wetland fills rapidly inresponse to rain events and tends to fill at the break of season in May or June each year. Surface wateror waterlogging persists as long as rain continues, usually until October. However, the wetland can dryout between rain events in this period.

Long term observations of salinity indicate that conditions are usually fresh or slightly saline (Ashton

2001), probably less than 1,000 mg/L. Reports of more saline conditions may have been made aftersignificant sea water intrusions after storm events (Fenner and Cleland 1935).

6.3 Water Regime

The structure of vegetation associations in the Washpool is closely related to the flooding pattern. Thewetland comprises three plant associations in the wetland basin (Samphire, Sea Club Rush Sedgelandand Exotic Grassland).

Samphire Shrubland

Water initially fills the lowest part of the wetland which borders the north side of Button Road. Waterlater spreads, possibly via a culvert, to the south of the road. These areas are vegetated with perennial

Samphire shrubs or bare mud (cracked clay in summer) in the lowest areas. When flooded, particularlyin spring, these areas are densely vegetated with submerged aquatic species including Widgeon grassand Swamp Crassula.

Towards the end of spring, when the wetland dries out, other low shrub and herbaceous plants grow,including Mallee Hemichroa, Trailing Hemichroa, Silky Wilsonia, Round-leaved Wilsonia andCreeping Brookweed (Kraehenbuehl 1995).

The plants present in this area are indicative of saline conditions. Although the Washpool may be freshwhen filled with stormwater, this internally draining area is likely to be the most saline as the systemdries out in summer. When the wetland is dry, any sea water inflows will pool in this area and mayconcentrate by evaporation to highly saline conditions.

This area is the most frequently flooded part of the system and receives water every year.

Sea Club-rush Sedgeland

As the wetland fills, water spreads outwards to flood the areas to the north and south, abutting thedrainage channel to the east. This area is seasonally flooded to a maximum depth of 300 mm and

supports dense stands of Sea Club-rush. Growth begins in late winter from underground tubers. Shoots

The Washpool

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grow to a height determined by the flooding depth, 0.5 to 1 m achieving their maximum density inNovember. The shoots die off in early summer to form a dense, grey thatch (Kraehenbuehl 1995).

The thatch persists until the wetland is flooded in May or June. The rotting plant material providesfood, shelter and substrates for aquatic algae, invertebrates and frogs, which in turn provide food forwaterbirds (Carpenter 2001).

The Sea Club Rush is favoured by annual flooding in winter and spring but tolerates occasional dryseasons. Waterlogged conditions are required for shoot growth. Persistently dry seasons will reducethe density of Sea Club Rush and favour invasive terrestrial species.

Exotic Grassland

The wetland basin increases in elevation towards the northern corner. The frequency of floodingdeclines towards the north as the bed level of the wetland exceeds the sill level of the outlet to the sea.This area is only temporarily flooded during storm events, when inflows exceed the capacity of theoutlet and water is temporarily backed up.

Towards the north the vegetation changes from a wetland community dominated by Samphire and Sea

Club-rush to a disturbed exotic grassland dominated by Sea Barley and Wild Oats. Other weed speciesinclude Artichoke Thistle, Soursob and Aster Weed (Valimanesh 1999).

Flooding can persist for several days in this area. In spring, inflows back up when the wetland isalready full. Large summer storm events can also flood this area. Flooding is too brief for wetlandspecies, such as Sea Club-rush, to dominate.

Inlet Channel

The inlet channel on the eastern boundary is enclosed on either side by ridges. The ridge to the west islower and allows high flows to spill into the wetland. The inlet channel is frequently and intermittently

flooded throughout the year. The channel includes pools up to 1 m deep, and shallower connectingsections. The banks are believed to be waterlogged for the greater part of the year.

Soil and surface water salinity appears to be lower than in the rest of the Washpool. It is frequentlyflushed by fresh stormwater and is above the level regularly affected by sea water inflow.

The deep pools support plants that require summer flooding including Common Reed and Cumbungi.The shallower sections of the channel are vegetated with meadow species that require persistentwaterlogging but tolerate only intermittent flooding. These plants include Streaked Arrow Grass,Prickly Arrow Grass, Monkey Flower and Emu Grass.

The banks of the ridges are believed to be waterlogged for a large proportion of the year and rarely, ifever, inundated. The dominant vegetation is tall, shrubby Smooth Cutting-grass. A number of Lignumshrubs are also present.

The Washpool

6-6

Dunes

The Washpool is isolated from the sea on the western side by sand dunes. The dunes are potentiallyflooded by large storm events but are usually exposed. The vegetation of the dunes includes speciesthat are tolerant of waterlogging, suggesting that the water that fills the Washpool seeps into the dunesand creates a perched water table in the overlying sands. Wetland plants growing in the dunes includeSea Rush, Bare Twig-rush and Knobby Club-rush.

6.4 Waterbirds

The conservation value of the Washpool is largely based on the waterbirds it supports. The followinggroups the waterbirds of the Washpool according to their dependence on water. Water requirementsare summarised in Table 2. Information is sourced from Carpenter (2001) and Ashton (2001).

Cape Barren Geese

Cape Barren Geese are grazing waterbirds that visit the Washpool when it is flooded. They tend to bepresent for only two months each year, arriving in September and remaining until the system dries out.The birds mainly graze pastures in the surrounding areas. Within the Washpool they graze grassesgrowing in the Samphire shrubland, such as Emu Grass, Barley Grass and Perennial Ryegrass.

Cape Barren Geese depend on flooding in the Washpool to provide a refuge from disturbance. Thebirds return to the water's edge when disturbed. They depend on the open landscape to provide a clearview of potential danger. They do not breed at the Washpool.

Crakes and Australasian Bittern

The Baillon's Crake, Australian Spotted Crake and Australasian Bittern depend on dense aquaticvegetation for shelter. They feed in the Sea Club-rush, occasionally also venturing into the nearby

flooded Samphire to feed on aquatic invertebrates, algal mats and seeds. The Australasian Bitterndepends particularly on frogs as a food source. These birds are shy and retreat quickly to the Sea Club-rush and Smooth Cutting-grass when disturbed.

These birds are present only when the Washpool is flooded, generally from September to October.

Wading Birds

Wading birds depend on mudflats and shallow flooded areas. Species in this group include White-faced Heron, White-necked Heron, Great Egret, Royal Spoonbill, Yellow-billed Spoonbill, Bitterns,Red-necked Avocet, Sandpipers, Snipe and Dotterels.

The Washpool

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Table 2. Water requirements of waterbirds at the Washpool

Group Species Habitat Requirements Water Requirements

Open Water Feeders Ducks, Black Swan,Whiskered Tern, Grebes,Cormorants

Flooding at any time ofyear.

Flooding to more than 200mm in winter and spring.

Absence of tall emergentmacrophytes

Summer drawdown toexclude Common Reedand Cumbungi.

Cape Barren Geese Cape Barren Goose Pasture in surroundingfarmland

n.a.

Refuge from disturbance,open vegetation for clearsight of threats

Flooding in Septemberand October.

Summer drawdown topromote samphire andexclude Common Reedand Cumbungi.

Occasional sea waterintrusion to control extentof emergent macrophytes.

Crakes and AustralasianBittern

Baillon's Crake, AustralianSpotted Crake,Australasian Bittern

Shallow flooding Flooding to more than 200mm in winter and spring.

Vigorous Sea Club-rushto support prey habitatrequirements

Flooding to 300 mm for 3months, August toOctober

Samphire for foraging andhunting

Seasonal winter/springflooding to provideexposed mud flats in latespring.


Smooth Cutting-grass forshelter from disturbance

Seasonal waterloggingand drainage of easternfringe to support SmoothCutting-grass

Wading Birds White-faced Heron,White-necked Heron,Great Egret, RoyalSpoonbill, YellowSpoonbill, Red-neckedAvocet, Sandpiper, Snipeand Dotterels

Flooding of sparsevegetation or open waterto 0-50 mm.

Seasonal winter/springflooding to provideexposed mud flats in latespring.


Vigorous Sea Club-rushto support prey habitatrequirements

Flooding to 300 mm for 3months, August toOctober

Cisticola Golden-headed Cisticola Smooth Cutting-grass forshelter

Seasonal waterlogging ofbanks of inlet channel.

The Washpool

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Wading birds visit the Washpool late in spring as the water level declines. They depend on shallow

flooding in sparse vegetation up to 50 mm deep and recently exposed wet mud. They predominantlyhunt aquatic invertebrates from the mud and water column, but larger birds (Egrets) may also huntfrogs and fish if present.

These species have a strong requirement for a seasonally fluctuating water level to provide suitableconditions for hunting as the water retreats. They require open areas with low growing vegetation,predominantly Samphire, but they also make some use of Sea Club-rush sedgeland.

The occasional intrusion of sea water to the Washpool is likely to be important in controlling thespread of emergent macrophytes such as Sea Club-rush. Samphire has a higher salinity tolerance thanemergent plant species and are an important component of wading bird habitat.

White-faced Heron have an important habitat linkage to Aldinga Scrub, where they breed in Red Gumat Cliffs Lagoon. Fledglings would come down to the Washpool to feed in November, if water ispresent.

Flooding generally ends too early in spring to support wading bird breeding. Black-winged Stilts and

Red-capped Dotterels breed sucessfully at similar wetlands nearby, and may also breed at theWashpool if flooding were extended into late spring and early summer.

Open Water Feeders

Birds that feed in open water include Ducks, Black Swan, Whiskered Tern, Grebes and Cormorants.This habitat component is present in the deeper areas in the central part of the Washpool, either side ofButton Road.

Cormorants (Little Pied, Pied, Little Black and Great) and Grebes (Australasian and Hoary-headed)are predatory and hunt mainly small fish, invertebrates and tadpoles. Black Swan and Ducks

(Australian Shelduck, Australind Wood Duck, Pacific Black Duck, Australasian Shoveler, Grey Teal,Chestnut Teal and Pink-eared Duck) are omnivorous. They hunt aquatic fauna such as invertebrates,tadpoles and fish and graze on soft-leaved submerged plants, such as Widgeon Grass and SwampCrassula.

Open water feeders make opportunistic use of water and visit whenever water is present. They can

arrive as early as July and remain as long as water persists. They have no strong seasonal waterrequirements.

Aldinga Scrub provides breeding habitat for ducks, particularly Australian Wood Duck, Black Duckand Grey Teal which nest in the substantial hollows provided by Red Gum. Fledglings are brought tothe Washpool to breed.

The Washpool

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Pacific Black Duck has bred at the Washpool. Breeding is regularly initiated by Black Swan, butgenerally fails because the wetland dries out before chicks can be raised to independence.

Golden-headed Cisticola

Golden-headed Cisticola are small shy birds that depend on the Smooth Cutting-grass on the easternboundary of the wetland to provide shelter. They feed in cereal crops, such as oats, if available nearbyand Sea Club-rush when present.


The water requirements of the Washpool are summarised in Table 3. The table presents the floodingphases of the wetland based on the periods at which water levels should be maintained to achievecritical ecosystem outcomes.

The annual flooding cycle of the Washpool is described in a series of four flooding stages which relateto important ecological stages through the year. The timing and duration of the stages indicates typicalconditions, which will vary from year to year depending on seasonal rainfall and temperatures. Thedepth at each stage and extent of flooding is estimated from the personal observations of GrahamCarpenter. Calibrated water level monitoring data are required to improve water level estimates.

The ecological significance of each stage is presented as Key Outcomes. These are the ecological

processes that define the character and diversity of the Washpool These outcomes must be achieved ineach flooding to maintain the ecosystem. The Key Outcomes are appropriate performance indicators ina future monitoring program.

The dry phase in late summer and autumn is an uneventful period for waterbirds. However, it isimportant in maintaining the samphire flats and open vegetation required for many waterbirds later in

the year. The accumulation of thatch from the spring growth of sedges provides an important substratefor invertebrates when the wetland is flooded. Periodic drying is important to maintain Saw-sedgehealth.

The wetland fills at the break of the season as drains discharge to the wetland and flush saline waterout to sea. Flooding in winter initiates production by aquatic fauna and emergent macrophytes.Opportunisitc waterbirds appear at this time.

Temporary deeper flooding is more likely to occur from September to November, particularly if the

catchment is saturated and the Washpool is already full. Under these conditions, flooding maytemporarily extend to the Grassland areas.

Few bird species breed at the Washpool, partly because water does not persist into early summer. TheWashpool could be enhanced by prolonging flooding at this time.

The Washpool

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The salinity of the Washpool is critical to its habitat value and closely related to the water regime. It isimportant that the salinity of the flooded system (from May to October) does not persistently exceed'brackish' levels (approximately 3,000 mg/L). Salinities below this concentration are required tosupport the aquatic fauna important to water birds, such as insect larvae, frogs, tadpoles and small fish.

A higher salinity would favour crustaceans and would exclude some of the water birds that depend onthe site.

The Washpool

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Table 3. Water Requirements of the Washpool

Timing Depth AboveWashpoolInvert

Salinity Vegetation Zone Inundation Key Outcomes

February toMay

Dry Salinisation byevaporation ofseawater inflows

All zones dry Temporary salinisation of wetland bed

Exclusion of tall emergent macrophtyes from Samphire zone

Accumulation of Sea Club-rush thatch

Resting stage for Samphire, Sea Club-rush, Saw-sedge

June toAugust

Flooded 100to 300 mm

Flushing byfresh stormwaterinflows

Samphire: 100 to 300 mm

Sea Club-rush: up to 100 mm

Saw-sedge: waterlogged

Grassland: dry

Invertebrate and frog production commences

Hunting by Open Water waterbirds

Recharge of perched aquifer below dunes

Sea Club-rush growth commences

Growth of Saw-sedge and Lignum

SeptembertoNovember

Flooded 300mm withintermittentpeaks up to400 mm

Flushing byfresh stormwaterinflows


Sea Club-rush: 100 to 300 mm

Saw-sedge: waterlogged

Grassland: up to 100 mm temporarily

Invertebrate and frog production continues

Hunting by Open Water waterbirds

Sea Club-rush growth continues

Refuge for Cape Barren Geese

Feeding by fledglings

Wading bird hunting

Growth of Saw-sedge and Lignum

Decemberto January

Flooded 100to 200 mmwithintermittentpeaks up to400 mm

Partialsalinisation byevaporatingstormwater andseawater inflows


Sea Club-rush: up to 100 mm

Saw-sedge: dry

Grassland: dry

Wading bird hunting

The Washpool

6-12

However, temporary salinisation is believed to be important. Sea water potentially enters duringparticularly high or storm tides. When the level in the Washpool is low, sea water accumulates andconcentrate in the wetland bed. The temporary salinisation of these areas is likely to be important inmaintaining the bare mud and Samphire, which is critical to the wading birds. If less saline conditions

were to occur, less suitable emergent macrophytes such as Sea Club-rush, Cumbungi and CommonReed may invade.

6.6 Changes in Water Regime

The hydrology of the Washpool has changed significantly through changes in the hydrology of thecatchment and through local drainage and earthworks. There is little specific information on thestructure of the original ecosystem, but the following observations can be interpreted from availabledata.

Size

The extent of the Washpool is believed to originally have been larger. Up to the 1930s the wetland was

continuous with Blue Lagoon, near Norman Road (Gardiner 1989). The extent of the main wetlandbasin is similar to early surveyors maps, but would have included an additional 600 m of flood proneland up to Norman Road. This former wetland area may have been flooded by:

• water backing up from the outlet to the sea;

• the overland movement of water via poorly defined channels from Blue Lagoon, Aldinga Scruband flood-prone land to the north and east; or

• both of these processes.

The area between the Washpool and Norman Road has been reclaimed and levelled and is cultivatedfor cereal crop production. Water flows past this area via deep well defined drains.

Depth

The Washpool is reported to have originally been flooded by up to 1.5 m into summer every year.

Sand was excavated from dunes between the wetland and the sea in the 1930s and 1940s to providebuilding material for the Myponga Reservoir (Gardiner 1989). It is possible that the sill level of theoutlet was lowered at this time. Potential flooding depth and duration of flooding would have beenreduced as water flowed out to sea more readily.

The original outlet must have been low enough to allow occasional sea water intrusion. There arereports of the wetland being saline (Fenner and Cleland 1935) or being fresh with occasional saline

events extending up to 100 m inland. However, if the sill were higher, saline conditions from sea waterintrusion may have lasted longer.

The Washpool

6-13

Outlet Location

The original outlet was located to the south of Button Road, but was relocated in the course of variousearthworks and excavations over the years to its present site just north of Button Road. The location ofthe outlet is not believed to be significant to the water and salinity regime of the wetland.

Flood-prone Area

The available flood-prone area in the wetland has declined. Sedimentology investigations show thatmost of the original wetland bed lay at 2.3 to 2.4 m AHD, which is the elevation of the current lowest

lying area (Dyson 2000). An additional 0.4 to 0.9 m of material has been added to approximately halfthe wetland since 1800, either through the dumping of fill or the deposition of sediment in stormwater.These areas are subject to only temporary inundation and do not provide long term wetland habitat.

Flow Duration

The duration and reliability of flooding has declined. Prior to the 1930s the Washpool was flooded upto 1.5 m deep through to summer, with permanent water present in the deepest area.

The original potential of the catchment to detain and slowly release runoff has declined, and inflowevents are now larger and more brief. Factors contributing to this change include:

• replacement of native vegetation with crops and pasture;

• construction of drains to capture and transfer runoff to the sea as quickly as possible; and

• isolation of Blue Lagoon, originally 2 m deep, which would have acted as a buffering storage forstormwater flows to the north.

The water table aquifer would also have acted as an important buffering storage. The aquifer to the

east and north was originally recharged principally by the ponding of stormwater from the SellicksHill Range. As drains were constructed to reduce the ponding of water on farmland east of theWashpool, the potential for groundwater recharge was reduced. The Washpool is located down-gradient of this aquifer and would have received a slow, persistent discharge of groundwater,extending the duration and reliability of flooding.

Furthermore, the drains are believed to have intercepted the water table. Engineering and WaterSupply Department engineers reported that the drains constructed after World War II flowedcontinuously for several years, indicative of groundwater interception (Nurton 1999). The potential forgroundwater discharge to support the Washpool may have declined.

Flooding in the Washpool is now closely related to individual storm events in the catchment becausewithout a buffering capacity in the catchment, inflows stop shortly after rainfall ends. The wetland is

vulnerable to dry periods between rain events in winter and spring and tends to dry shortly afterreliable rainfall ends in October.

The Washpool

6-14


Objectives

Although the hydrology and ecology of the Washpool has changed since development of the region,the current ecosystem structure is valuable and should be preserved. It represents an importantcomponent of the original system of coastal wetlands in the area and it supports threatened species andplant communities. Enhancement of the Washpool should focus on protecting and improving thecurrent characteristics of the ecosystem as a freshwater coastal marsh.

Prolonging Inflows

The capacity of the Washpool to support breeding bird populations is compromised by the alteredcharacteristics of inflows. Changes in the catchment, particularly land clearance and drainage, result inrainfall runoff being delivered to the Washpool more quickly and in shorter, larger flow events. Thewetland has a small capacity to retain water due to the low sill level to the sea. The water level

consequently falls soon after rain events end, making the system vulnerable to dry periods withinwinter and spring and prone to dry out soon after warm weather begins around October.

The wetland would be enhanced by damping the current peaks in flow. Reducing the size andprolonging the duration of flows would reduce the probability of dry periods in winter and spring andincrease the probability of flooding persisting into November and December. Birds which regularlyattempt, but fail, to breed would be favoured by damped inflows: Black Swan, Black-winged Stilts,Red Capped Dotterels and several other species.

Any changes in water regime must allow the system to dry out in summer and autumn to maintain thevegetation structure and salinity balance of the current ecosystem.

Linked Ecosystems

The wetland would be enhanced by restoring the adjacent and ecologically linked ecosystems at theWashpool and Aldinga Scrub.

The deep water habitat of Blue Lagoon was originally adjacent to and continuous with the shallowmarsh of the Washpool. The two ecosystems would have complimented each other through the

exchange of aquatic fauna, plant propagules and the provision of refuges from disturbance such asdrought or fire in either site. Fauna living in Aldinga Scrub would also have used these ecosystems assites for grazing, foraging, hunting, watering and nesting.

Restoring the linkages will increase the range of habitats available to fauna in the area and mayincrease the biodiversity of the site.

Recommendations

7-1

7 Recommendations

7.1 Conclusions and Management Objectives

The coastal ecosystems of Aldinga Scrub, Blue Lagoon and the Washpool have been significantly

altered through the drainage of the Silver Sands Catchment and various intrusive earthworks. Theprincipal hydrological changes are presented in Table 4.

Aldinga Scrub is dependent on flooding associated with the underlying perched water table. The extentand duration of flooding appears to have declined due to the diversion of stormwater north of AldingaBeach Road, the drainage of flooded land to the east of the Scrub and the interception of the perchedwater table by drains. The wetland vegetation of the Scrub may be drought-stressed and in transition to

a more terrestrial community. Action is required to provide the water to sustain the current ecosystem.Action includes recharge of the perched water table and provision of surface water flows.

Table 4. Summary of interpreted hydrological impacts on ecosystems.

Catchment Change Hydrological Change Probable Impact on

Ecosystems

Land clearance in catchment Increased runoff, flows of greater

magnitude but shorter duration

Water levels fluctuate more,flooding more intermittent, flooding

ends earlier in season.

Drains capture and transfer

surface water

Increased runoff, flows of greater

magnitude but shorter duration

Water levels fluctuate more,flooding more intermittent, flooding

ends earlier in season.

Diversion of water down

Sellicks Beach Road

Reduced inflow to Washpool Water levels fluctuate more,flooding more intermittent, flooding

ends earlier in season

Water table lowered by drains

east of Washpool

Reduced groundwater flow Water levels fluctuate more,flooding more intermittent, flooding

ends earlier in season

Drains divert water from Blue

Lagoon directly to Washpool

Reduced inflow to Blue Lagoon Flooding rare and shallow

Increased inflow to Washpool Increased flooding depth and

duration

Catchment north of Aldinga

Beach Road diverted to sea

Reduced runoff Flooding of Aldinga Scrub wetlandsless frequent and of shorter

duration, waterlogging of scrub

Sedimentation in Washpool Reduced storage Flooding shallower, more

intermittent

Reduction in size of dunes at

Washpool

Increased sea water exchange,

reduced storage

Reduced flooding depth, increasedfrequency of saline episodes,

reduced flooding duration

Sill in Washpool outlet Reduced sea water exchange,

increased storage

Increased flooding depth, reducedfrequency of saline episodes,

increased flooding duration

Recommendations

7-2

The proposed management objective for Aldinga Scrub is therefore:

"to provide a suitable surface water and groundwater regime to maintain the health of phreatophyticwoodland vegetation and to restore the former water regimes of wetlands and waterholes."

Blue Lagoon is a small isolated depression vegetated with Lignum. Despite the regional conservationsignificance of Lignum, the wetland has little habitat value for vertebrate fauna. The ecosystemreflects the water regime it currently receives and no action is required to provide its waterrequirements. Blue Lagoon was formerly a permanent deep water habitat. Restoration of this habitatwould have significant biodiversity benefits for the Washpool and Aldinga Scrub.

The proposed management objectives for Blue Lagoon are therefore:

"to preserve the remnant of Blue Lagoon as an isolated Lignum Shrubland; and

to recreate the deep water habitat formerly provided by Blue Lagoon and to restore the continuous

habitat linkage between Aldinga Scrub and the Washpool in a new constructed wetland, in the vicinityof the original Blue Lagoon site on modified farming land."

The Washpool is a low-lying, shallow coastal marsh that receives stormwater collected in the SilverSands catchment before it flows out to sea. The Washpool provides an important water bird habitat,particularly for wading species. It also supports several rare and threatened plants. The ecology of theWashpool reflects the current water regime and no action is required to provide its water requirements.

However, the ecosystem could be significantly enhanced through hydrological works to reduce flowpeaks and to prolong flooding.

The Washpool has been significantly altered from its original structure over the past 100 years,particularly in becoming shallower and seasonally dry. However, it now has new significantconservation values in its own right which should be preserved. If required, the habitats formerlyfound in the Washpool could be created nearby in a constructed wetland, possibly near Blue Lagoon.

The proposed management objectives for the Washpool are therefore:

"to maintain the new environment of the Washpool as a wading bird habitat; and

to promote waterbird breeding, waterbird carrying capacity and plant and animal diversity byincreasing the extent and duration of flooding in the wading bird habitat."

7.2 Recommendations

Restoration of Perched Water Table

It is proposed that a wetland is constructed on Hart Road north of Aldinga Scrub to recharge theperched aquifer and provide surface flooding to wetland areas. This has previously been proposed byKinhill (1988) to manage stormwater run-off from urban development in this area. The wetland could

Recommendations

7-3

be designed to leak to the perched aquifer beneath the Scrub. The wetland would provide habitat andwould compensate to some extent for the loss to wetland habitat to drainage elsewhere in the area.

In engineering terms, the constructed wetland would function as a stormwater retention and anartificial recharge pond (what is described by ASCE, 2001, as an off-channel pond). An importantconsideration in the design of such a system would be an understanding of the physiochemical natureof both stormwater and shallow soils so that allowance can be made for physical, chemical and

biological clogging of the infiltrating soils surface (Bouwer, undated). Phased construction isrecommended, so that pilot trial(s) provide operating experience as the full-scale system is designed.

The construction of a wetland in the northern part of the Scrub would be designed to compensate forreduced surface (stormwater) drainage from north of Aldinga Beach Road. For this reason it may benecessary to incorporate a system in the design of the wetland that can divert excess-to-needsstormwater away from the wetland.

Control of Flow Peaks in the Washpool

Flows to the Washpool occur in shorter, larger peaks than previously, resulting in a premature end toflooding each spring and lost opportunities for wetland fauna to breed.

The detention of stormwater within the catchment could assist in damping stormwater peaks andprolonging flooding. Stormwater detention basins could be designed to capture and slowly releasestorm flows downstream and may also have an engineering benefit in controlling flooding.

Restoration of Blue Lagoon

Blue Lagoon was formerly a large, deep perennial wetland. It is now small and only temporarily filledby direct rainfall.

The permanent deep water wetland habitat originally provided by Blue Lagoon could be created

through the construction of a stormwater wetland near Norman Road. The wetland would receiveinflows from the drain below Norman Road and detain them before release to the Washpool. A deepwater envirionment could be created between the Washpool and Norman Road, to the east of the BlueLagoon remnant.

The wetland would provide a complimentary habitat to the Washpool and Aldinga Scrub by providing

a drought refuge for aquatic fauna and a contrasting habitat type to increase biodiversity. The newwetland would be connected to the Washpool via flow paths and would provide opportunities forfauna exchange.

A constructed wetland would assist in prolonging flows to the Washpool by detaining and slowlyreleasing stormwater. This would assist in extending seasonal flooding in the Washpool and maypromote breeding by water birds.

Recommendations

7-4

Increase Flood Duration and Extent in the Washpool

The area of the Washpool subject to regular inundation is believed to have declined throughsedimentation, the dumping of fill, land reclamation and water regime manipulation. Some areas ofrecent deposition are identified by Dyson (2000). These recent materials could be excavated toincrease the extent of shallow flooding and available wetland habitat.

The level of the outlet sill could be raised to increase the depth, extent and duration of flooding. A

higher sill would also reduce the inflow of sea water the salinity of the wetland. A hydrological andecological assessment would be required to ensure that the important elements of the water regimewere maintained; that the wetland dries out in autumn and that the wetland bed remains dominated bysamphire.

Limitations

These proposals must be developed with care to avoid disturbance to existing ecosystems. The risk tobird life associated with earthworks for a constructed wetland at Norman Road should be assessed.

The Washpool is known to be a site of considerable Aboriginal cultural significance, with many

artifacts present in the area. The risk of disturbance to Aboriginal cultural values should be assessed inany plans involving earthworks.

Water regime manipulation may present risks of flooding to adjacent land. Flooding risks should beassessed in detail.

Further Investigations

It is recommended that a detailed and calibrated catchment flow model is developed to predictmonthly inflows to system for a range of event probabilities. The model is required to provide adviceon:

• hydrological parameters for the design of restored Blue Lagoon (size, depth, extent, floodduration); and

• scope to reduce and prolong flow peaks to the Washpool through detention structures in thecatchment, a wetland at Hart Road, a restored Blue Lagoon and any combination of these.

This will involve further assessment of in the design phase of the stormwater system.

It is recommended that a topographic survey is undertaken of the Washpool including surroundingflood prone land, enclosing banks and the outlet sill.

Recommendations

7-5

Monitoring

It is recommended that the current groundwater monitoring program in Aldinga Scrub and theWashpool is maintained. It is recommended that an additional shallow bore is installed on Justs Roadnear Button Road to monitor potential shallow groundwater discharge from the east.

It is recommended that surface water levels are monitored weekly in the Washpool and Cliffs Lagoon.Levels should be monitored against permanent graduated staffs calibrated to the Australian Height

Datum. Accurate water level information will enable more accurate estimates of environmental waterdeficiencies and requirements.

It is recommended that permanent vegetation transects are established in Aldinga Scrub in waterholesand other wetland areas. The transects should be used to identify transitions in vegetation structure onthe elevation gradient from waterlogged and flood-prone areas to terrestrial vegetation in highelevation areas. Long term monitoring, undertaken annually, will describe the response of vegetationto change in the elevation of the perched water table.

References

8-1

8 References

Ashton, C.B. (2001). Birds at the 'Washpool', Sellicks Beach, an ephemeral degraded swamp, prior toplanned restoration. South Australian Ornithologist 33 (8): 145-155.

ASCE. (2001). Standard Guidelines for Artificial Recharge of Ground Water. Environmental andWater Resources Institute, American Society of Civil Engineers. EWRI/ASCE 34-01.

Australian Cultural Heritage Management (1999). An Aboriginal (Kaurna) Cultural HeritageAssessment for the Proposed Re-instatement of the Aldinga Washpool, South Australia. Stage One.Report prepared for The City of Onkaparinga, Noarlunga Centre.

Bouwer H. (undated). Artificial Recharge of Groundwater: Systems and Guidelines. In: GroundwaterResources: Assessment and Management. Wairaki Research Centre Taupo. New Zealand.

Campbell, V.M. (1988). The coastal archaeology of the Fleurieu Peninsula. Unpublished MA Thesis,The Flinders University of South Australia.

Carpenter, G. (2001). Habitat use by waterbirds at the Washpool wetland, Aldinga 1999-2000. Reportprepared for the Friends of Aldinga Scrub Conservation Park.

Clarke D. and Graham, J. (2002). Aldinga Scrub Conservation Park Groundwater Piezometer SurveyReport. DWLBC, June 2002.

CoffeyGeosciences (2000). City of Onkaparinga Aldinga Beach Wetlands Button Road, AldingaBeach Groundwater and Environmental Investigations. Ref. A3337/1-AB.

Dyson, I.A. (2000). Evolution of the Aldinga Washpool in the Last 200 Years. Report ref Version 1.0prepared for the City of Onkaparinga, Noarlunga Centre.

Ecological Associates (2002). Investigation of Groundwater Dependent Ecosystems in the McLarenVale Prescribed Wells Area. Ref. AE001.

Fatchen and Associates (1986). Northern Aldinga Scrub Vegetation and Groundwater. Report ref KSR19 86 prepared for Kinhill Stearns, Adelaide.

Fenner, C. and Cleland, J.B. (1935). The geography and botany of the Adelaide Coast. FieldNaturalists Section of the Royal Society of South Australia, Publication Number 3.

Gardiner, G. (1989). History. In Aldinga Sellicks Scrub Report, Wollaston, E. M. (Ed). NatureConservation Society of South Australia, Adelaide.

Field Naturalists Society (1990). Concept Management Plan for the Aldinga Scrub Conervation Park(Draft). Field Naturalists Society, Adelaide.

Golder Associates (1995). Geotechnical Investigation Proposed Acacia Street Drainage AldingaBeach South Australia. Ref. 95661161/2.

Kinhill (1988). Draft Environmental Impact Statement Sellicks Beach Marina – Residential Project.Prepared for District Council of Willunga. October 1988.

References

8-2

Kinhill Engineers (1995). Aldinga Beach Drainage Study. Final Report ref AE4092 002 Rev 0prepared for District Council of Willunga and Department of Housing and Urban Development,Adelaide.

Kinhill Engineers (1996). Washpool Wetland Lagoon Re-establishment. Report prepared ref. AE6067C DO 001 Rev C for District Council of Willunga, Willunga.

Kraehenbuehl, D.N. (1995). Letter from The Field Naturalists Society of South Australia to WillungaDistrict Council, Willunga.

Kraehenbuehl, D.N. and Smith, T. (1989). Native vegetation. In Aldinga Sellicks Scrub Report,Wollaston, E. M. (Ed). Nature Conservation Society of South Australia, Adelaide.

Nurton, D. (1989). Letter from Dave Nurton, Friends of the Earth Willunga to Mr Bob Ware, ManagerAboriginal Heritage Brach, Department of Environment and Planning South Australia.

Nurton, D. (1995). An overview of the Washpool and its Environment Significance. Focus on theWashpool, Seminar held at McLaren Vale, District Council of Willunga.

PIRSA 2003. Yankalilla 6527-II Barker SI5413, 1:50,000 Geological Map, Department of PrimaryIndustries and Resources, South Australia.

Selby J. and Lindsay, J.M. (1982). Engineering Geology of the Adelaide City Area. South AustralianDept. of Mines and Energy. Bulletin 51

Tindale, N.B. (1987). The Wanderings of Tjirbruki: a tale of the Kaurna people. Records of the SouthAustralian Museum 20: 5-13.

Wegener, J.E. (1995). The Relationship between Sedimentation on Aldinga Reef, and Washpool Creekand Sellicks Creek Catchments, Willunga Basin. Unpublished Honours thesis, Department ofGeography, The University of Adelaide.

Wood, V. (1996). Aboriginal heritage desktop study for the proposed re-establishment of theWashpool lagoon and wetlands, Aldinga. A report to Kinhill Engineers Pty Ltd, Parkside SA.

Valimanesh, A. (1999). Aldinga Washpool Lagoon Vegetation and Revegetation Management Plan.Stage 1: Remnant vegetation and weed management. Report prepared for the City of Onkaparinga.

Figures

270000

270000

6090

000

6090

000

ALDINGA SCRUB & WASHPOOL LAGOON

LOCALITY PLAN

Figure

1Project AV-01

September 2002

0 0.25 0.5 0.75 10.125Kilometres

Document: \\Eserver\rem\GIS\Eco Assoc\washpool.mxd

Gulf

St

Vincent

Quaternary

Depth to Groundwater (mBGL)< 2.52.5 - 5.05.0 - 10.010.0 - 15.0> 15.0

Note: the watertable occurs for the major part of the zone in Quaternary sediments, with some exceptions in the north where the Port Willunga Formation outcrops.

WashpoolLagoon

BlueLagoon

Marcus Cooling

BUTTON

NORMAN

JUSTS

Gulf

St Vincent

BLUELAGOON

ROAD

RO

AD

ROAD

THEWASHPOOL

SamphireSeaClub-rush

Samphire

Drain

Drain

Coas

tal

Veg

etat

ion

Dune

Saw-sedge and Lignum

Main Inlet Channel


Pasture

Pasture

Saw-sedge

Saw-sedge

Saw-sedge

Sam- phire

ACAC

IA TCE

JUSTS

RO

AD

MA

IN

SOU

THR

OA

D

COX ROAD

HART ROAD

ALDINGA

SCRUB

CONSERVATION

PARK

KESTREL TC

E

ESPLANAD

E

ACAC

IA TCE

QUONDONG AVE

ESPLANAD

E

DO

VERSTR

EET

RO

WLEY

RO

AD

ALDINGA BEACHROAD

Drain

Drain

Drain

Drain

Drain

Drain

Cliff'sLagoon

FormerBlackfellow'sWaterhole

SalineWaterholes

Interpreted overland flow

path

AldingaBeach

Figure 2.

Aldinga Scrub, The Washpool and Blue Lagoon

Not to Scale: 250 m (approx)

N

SalineWaterholes

Red Gumand Lignum

HO

WR

D

SilverSandsBeach

KEY:

(NOT TO SCALE)

FIGURE

Plan sourced from PIRSA (2003) September-02

GEOLOGICAL SETTING

3

N

The Washpool

Aldinga Scrub

Aldinga Scrub

FIGURE

Base plan sourced from Clarke and Graham (2002) September-02

ELEVATION OF THE UPPER SURFACE OF HINDMARSH CLAY 4

5.0

7.5

10.0

12.5

15

16.6

15.8

13.5

12.6 12.8

11.3

9.59.5

4.6

1.7

DRAIN

Approximate Scale

0.3 0 0.3 0.6km

INTERPRETED UPPER ELEVATION OF HINDMARSH CLAY (dashed = inferred)

WLG136

WLG135

WLG125

WLG134WLG127

WLG132

WLG129

WLG138

WLG128

WLG126

WLG137

WLG130

WLG133

WLG131

WLG129 MONITORING WELL

FIGURE


INTERPRETED PERCHED AQUIFERGROUNDWATER LEVELS

mAHD 25/6/02 5

15

10

5

16.81

16.05

14.97

13.78

11.97

7.26

4.45

DRAIN

Approximate Scale

0.3 0 0.3 0.6km

INTERPRETED GROUNDWATER CONTOUR (dashed = inferred)

INTERPRETED GROUNDWATER FLOW DIRECTION

WLG136

WLG135

WLG125

WLG134WLG127

WLG132

WLG129

WLG138

WLG128

WLG126

WLG137

WLG130

WLG133

WLG131


FIGURE


INTERPRETED DEPTH TO WATERPERCHED WATER TABLE AQUIFER (m)

25/6/02 6

2 mgbl

1 mgbl

2.2

1.8

1.5

1.26

6.25

0.64

DRAIN

Approximate Scale

0.3 0 0.3 0.6km

INTERPRETED DEPTH TO PERCHED WATER TABLE CONTOUR (dashed = inferred)

WLG136

WLG135

WLG125

WLG134WLG127

WLG132

WLG129

WLG138

WLG128

WLG126

WLG137

WLG130

WLG133

WLG131


FIGURE

Base plan sourced from Clarke and Graham (2002) Septmeber-02

INTERPRETED PERCHED AQUIFER SALINITY (mg/L)

April 2002 7

10,000

5,000

1,732

8,327

19,816

DRAIN

Approximate Scale

0.3 0 0.3 0.6km

INTERPRETED SALINITY CONTOUR

WLG136

WLG135

WLG125

WLG134WLG127

WLG132

WLG129

WLG138

WLG128

WLG126

WLG137

WLG130

WLG133

WLG131


11,904

9,078

FIGURE


INTERPRETED PORT WILLUNGA FORMATION GROUNDWATER LEVELS

(mAHD) 25/6/02 8

1.0 mAHD

1.1 mAHD

1.2 mAHD

0.88

1.37

0.92

1.23

1.28

DRAIN

Approximate Scale

0.3 0 0.3 0.6km

INTERPRETED GROUNDWATER CONTOUR (dashed = inferred)

INTERPRETED GROUNDWATER FLOW DIRECTION

WLG136

WLG135

WLG125

WLG134WLG127

WLG132

WLG129

WLG138

WLG128

WLG126

WLG137

WLG130

WLG133

WLG131


0.79

FIGURE


INTERPRETED PORT WILLUNGAFORMATION SALINITY (mg/L)

April 2002 9

1,000 mg/L

5,000 mg/L

10,000 mg/L

3,712

10,878

2,165

4,740

5,904

1,119

DRAIN

Approximate Scale

0.3 0 0.3 0.6km

INTERPRETED SALINITY CONTOUR

WLG136

WLG135

WLG125

WLG134WLG127

WLG132

WLG129

WLG138

WLG128

WLG126

WLG137

WLG130

WLG133

WLG131


FIGURE

Base plan sourced from Clarke and Graham (2002)

INTERPRETED THICKNESS OF HINDMARSH CLAY (m) 10

5

10

15

3.0

3.0

4.88.6

19.511.6

9.5

17.1

DRAIN

Approximate Scale

0.3 0 0.3 0.6km

INTERPRETED THICKNESS CONTOUR

WLG136

WLG135

WLG125

WLG134WLG127

WLG132

WLG129

WLG138

WLG128

WLG126

WLG137

WLG130

WLG133

WLG131


BUTTON

NORMAN

JUSTS

Gulf St Vincent

SilverSandsBeach

BLUELAGOON

ROAD

RO

AD

ROAD

THEWASHPOOL

ExoticGrassland

Samphire Sea Club-rush

Lignum

Samphire

Drain

Drain

Coas

tal D

une

Veg

etat

ion

Coas

tal

Veg

etat

ion

Dune


Main Inlet Channel


Pasture

Pasture

Pasture

Pasture

Saw-sedge

Saw-sedge

Saw-sedge

Sam- phire

CoastalDuneVegetation

RO

AD

TERR

ACE

ESPLANAD

E

Drain

SalineWaterholes

Pasture

ALDINGASCRUB

N

Figure 11.

Vegetation Communities of the Washpool and Blue Lagoon

Not to Scale: 250 m (approx)

Appendix AGroundwater Monitoring Data

Groundwater Levels

Semaphore SandUnit No Obs No Obs Date SWL(m) SWL(mAHD)

6527-01112 WLG126 28-03-88 no reading6527-01112 WLG126 09-04-02 Dry6527-01112 WLG126 02-05-02 Dry6527-01112 WLG126 03-05-02 Dry6527-01112 WLG126 29-05-02 Dry6527-01112 WLG126 25-06-02 1.26 13.786527-01114 WLG128 28-03-88 no reading6527-01114 WLG128 09-04-02 1.87 15.346527-01114 WLG128 02-05-02 Dry6527-01114 WLG128 03-05-02 Dry6527-01114 WLG128 29-05-02 Dry6527-01114 WLG128 25-06-02 2.24 14.976527-01115 WLG129 28-03-88 no reading6527-01115 WLG129 12-04-02 Dry6527-01115 WLG129 02-05-02 no reading6527-01115 WLG129 29-05-02 no reading6527-01115 WLG129 25-06-02 1.5 16.816527-01116 WLG130 28-03-88 no reading6527-01116 WLG130 11-04-02 -0.02 11.786527-01116 WLG130 02-05-02 -0.1 11.866527-01116 WLG130 03-05-02 -0.1 11.866527-01116 WLG130 29-05-02 -0.22 11.986527-01116 WLG130 25-06-02 -0.21 11.976527-01118 WLG131 05-04-88 2.12 8.336527-01118 WLG131 11-04-02 Dry6527-01118 WLG131 02-05-02 Dry6527-01118 WLG131 03-05-02 Dry6527-01118 WLG131 29-05-02 Dry6527-01118 WLG131 25-06-02 no reading6527-01121 WLG133 07-04-88 1.82 3.276527-01121 WLG133 10-04-02 1.57 3.526527-01121 WLG133 02-05-02 1.64 3.456527-01121 WLG133 03-05-02 1.64 3.456527-01121 WLG133 29-05-02 1.28 3.816527-01121 WLG133 25-06-02 0.64 4.456527-01128 WLG137 28-03-88 no reading6527-01128 WLG137 10-04-02 Dry6527-01128 WLG137 02-05-02 Dry6527-01128 WLG137 03-05-02 Dry6527-01128 WLG137 29-05-02 Dry6527-01128 WLG137 25-06-02 6.25 7.266527-01129 WLG138 28-03-88 no reading6527-01129 WLG138 10-04-02 2.47 15.46527-01129 WLG138 02-05-02 no reading6527-01129 WLG138 03-05-02 Dry6527-01129 WLG138 29-05-02 no reading6527-01129 WLG138 25-06-02 1.82 16.05


Port Willunga FormationUnit No Obs No Obs Date SWL(m) SWL(mAHD)

6527-01111 WLG125 25-03-88 13.30 1.746527-01111 WLG125 09-04-02 14.38 0.666527-01111 WLG125 02-05-02 14.36 0.686527-01111 WLG125 03-05-02 14.36 0.686527-01111 WLG125 29-05-02 14.2 0.846527-01111 WLG125 25-06-02 14.12 0.926527-01117 WLG127 04-04-88 8.43 2.076527-01117 WLG127 11-04-02 9.76 0.746527-01117 WLG127 02-05-02 9.73 0.776527-01117 WLG127 03-05-02 9.73 0.776527-01117 WLG127 29-05-02 9.81 0.696527-01117 WLG127 25-06-02 9.71 0.796527-01120 WLG132 07-04-88 3.36 1.736527-01120 WLG132 10-04-02 4.22 0.876527-01120 WLG132 02-05-02 4.23 0.866527-01120 WLG132 03-05-02 4.23 0.866527-01120 WLG132 29-05-02 3.86 1.236527-01120 WLG132 25-06-02 3.86 1.236527-01122 WLG134 13-04-88 10.70 0.756527-01122 WLG134 11-04-02 10.51 0.946527-01122 WLG134 02-05-02 11.09 0.366527-01122 WLG134 03-05-02 11.09 0.366527-01122 WLG134 29-05-02 10.88 0.576527-01122 WLG134 25-06-02 10.57 0.886527-01123 WLG135 14-04-88 13.70 1.506527-01123 WLG135 10-04-02 14.56 0.646527-01123 WLG135 02-05-02 14.5 0.76527-01123 WLG135 03-05-02 14.5 0.76527-01123 WLG135 29-05-02 13.91 1.296527-01123 WLG135 25-06-02 13.83 1.376527-01125 WLG136 20-04-88 1.71 1.976527-01125 WLG136 11-04-02 2.75 0.936527-01125 WLG136 02-05-02 2.85 0.836527-01125 WLG136 03-05-02 2.75 0.936527-01125 WLG136 29-05-02 2.7 0.986527-01125 WLG136 25-06-02 2.4 1.28


Groundwater Salinity

Semaphore SandUnit No Obs No Collect Date EC TDS6527-01114WLG128 09-04-02 3120 17326527-01117WLG127 11-04-02 20100 119046527-01116WLG130 11-04-02 32100 198166527-01120WLG133 11-04-02 15580 90786527-01121WLG133 05-07-02 14570 84586527-01129WLG138 10-04-02 14370 8327

Port Willunga FormationUnit No Obs No Collect Date EC TDS6527-01111WLG125 13-03-01 5910 33006527-01111WLG125 09-04-02 6600 37126527-01111WLG125 02-05-026527-01120WLG132 11-04-02 8370 47406527-01120WLG132 05-07-02 8480 48056527-01122WLG134 11-04-02 3890 21656527-01123WLG135 11-04-02 18500 108786527-01123WLG135 25-06-02 14830 86096527-01123WLG135 05-07-02 19500 115076527-01125WLG136 11-04-02 2170 1199


Port Willunga Formation: Groundwater Hydrographs Washpool Lagoon and Aldinga Scrub Hydrogeological Assessment

WLG125

13.5

14

14.5

15

Apr-02 May-02 Jun-02

Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG127

9

9.5

10

10.5


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG132

3

3.5

4

4.5


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG134

10

10.5

11

11.5


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG135

13.5

14

14.5

15


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG136

1.5

2

2.5

3


Month

Dep

th t

o G

rou

nd

wat

er

(m)


Semaphore Sand: Groundwater Hydrographs

WLG126

0.5

1

1.5

2


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG128

1.5

2

2.5

3


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG129

1

1.5

2

2.5


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG130

-0.5

0

0.5

1


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG133

0.5

1

1.5

2


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG138

1.5

2

2.5

3


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG137

5.5

6

6.5

7


Month

Dep

th t

o G

rou

nd

wat

er

(m)

Washpool Lagoon and Aldinga Scrub Hydrogeological Assessment

WLG138

1.5

2

2.5

3


Month

Dep

th t

o G

rou

nd

wat

er

(m)

WLG137

5.5

6

6.5

7


Month

Dep

th t

o G

rou

nd

wat

er

(m)

Appendix BClimate Data

MACINTOSH HD:EASSOC:PROJECTS:AE002 WASHPOOL:REPORT:FINAL REPORT:FINAL REPORT.DOC\24-JAN-03

Rainfall Data

Average Rainfall (mm/month) Washpool Lagoon and Aldinga Scrub Hydrogeological AssessmentJan 16.5Feb 18.1Mar 21.7Apr 39.9

May 62.1Jun 72.4Jul 70.8

Aug 61.8Sep 51.3Oct 40.7Nov 25Dec 21

Evaporation = 1,410 mm/yr

0

20

40

60

80

100

Jan-

01

Feb

-01

Mar

-01

Apr

-01

May

-01

Jun-

01

Jul-0

1

Aug

-01

Sep

-01

Oct

-01

Nov

-01

Dec

-01

Month

Rai

nfa

ll (m

m/m

on

th)

Appendix CSpecies Referred to in Text


Common Name Scientific Name

PLANTS

Aster Weed Aster subulatus

Bare Twig-rush Baumea juncea

Bare Twig-rush Baumea juncea

Barley Grass Critesion murinum

Beard-heath Leucopogon sp.

Bitter Quandong Santalum murrayanum

Black Bristle-rush Chorizandra enodis

Common Fringe-myrtle Calytrix tetragona

Common Reed Phragmites australis

Creeping Brookweed Samolus repens

Cumbungi Typha sp.

Drooping Sheoak Allocasuarina verticillata

Golden Wattle Acacia pycnantha

Heath Tea-tree Leptospermum myrsinoides

Knobby Club-rush Isolepis nodosa

Lignum Muehlenbeckia florulenta

Loose-flower Rush Juncus pauciflorus

Mallee Box Eucalyptus porosa

Mallee Hemichroa Hemichroa diandra

Milfoil Myriophyllum spp.

Monkey Flower Mimulus repens

Nardoo Marsellia drummondi

Notched Sedge Carex bichenoviana

Pale Rush Juncus pallidus

Perennial Ryegrass Lolium perenne

Pink Gum Eucalyptus fasciculosa

Pondweed Potamogeton spp.

Prickly Arrow-grass Triglochin mucronatum

Quandong Santalum acuminatum

Red Gum Eucalyptus camaldulensis

Round-leaved Wilsonia Wilsonia rotundifolia

Rush Juncus spp.

Samphire species Halosarcia pergranulata

Sea Barley Critesion maritima

Sea Box Alyxia buxifolia

Sea Club-rush Bolboschoenus caldwellii

Appendix CSpecies Referred to in Text


Common Name Scientific Name

Sea Rush Juncus kraussii

Smooth Cutting-grass Gahnia filum

Stiff Flat-sedge Cyperus vaginatus

Spiny Flat-sedge Cyperus gymnocauolos

Streaked Arrow-grass Triglochin striatum

Swamp Crassula Crassula helmsii

Trailing Hemichroa Hemichroa pentandra

Widgeon Grass Ruppia sp.

Wild Oats Avena barbata

BIRDS

Australasian Shoveler Anas rhynchotis

Australasian Bittern Botaurus poiciloptilus

Australian Shelduck Tadorna tadornoides

Australian Spotted Crake Porzana fluminea

Australian Wood Duck Chenonetta jubata

Baillon's Crake Porzana pusilla

Black-tailed Native Hen Gallinula ventralis

Cape Barren Goose Cereopsis novaehollandiae

Chestnut Teal Anas castanea

Darter Anhinga melanogaster

Golden-headed Cisticola Cisticola exilis

Great Egret Ardea alba

Grey Teal Anas gracilis

Little Pied Cormorant Phalacrocorax melanoleucos

Pacific Black Duck Anas superciliosa

Pink-eared Duck Malacorhynchus membranaceus

Purple Swamphen Porphyrio porphyrio

Red-necked Avocet Recurvirostra novaehollandiae

Royal Spoonbill Platalea regia

Sandpipers Calidris spp.

Snipe Gallinago spp.

White-faced Heron Ardea novaehollandiae

Yellow-billed Spoonbill Platalea flavipes

Documents

Environmental Water Requirements of Aldinga Scrub, Blue ... · PDF fileEnvironmental Water Requirements of Aldinga Scrub, Blue Lagoon and the Washpool The City of Onkaparinga and The