Wetland Conservation at Esperance WA

Recommendations for the Management of the Coomalbidgup Swamp wetlands

A report produced by Green Skills for the Natural Heritage Trust and the Water and Rivers Commission

by Wetland project officer Kevin Hopkinson

December 2002

1 Acknowledgments

Green Skills and the Water and Rivers Commission would like to thank the following people for their involvement and assistance with the production of this report.

Louise and John Gray, Coomalbidgup Landholders, for catchment information, planning help and tracking down other farmers. Special thanks to Louise for helping with catching bugs and taking water samples down at the swamp.

John Simons Hydrologist and Stephen Gee, Mapping Technical Officer, Department of Agriculture, Esperance for providing advice and catchment information.

All the landholders who permitted site visits including John and Louise Gray, Rex Mutch, and the Lanes.

Support and advice from Water and Rivers Commission staff particularly Regional Manager, South Coast Region Naomi Arrowsmith and Albany District Manager Chris Gunby.

Support and advice from Green Skills staff including Project Manager Basil Schur.

Field work, photography and report compilation by Kevin Hopkinson.

2 Do you have any comments or feedback you would like to give?

This report is intended to generate community discussion as to the most practical and effective management practices that can be incorporated into the catchment planning activities of the Coomalbidgup Swamp Catchment area.

If you have any comments on the recommendations provided in this report, Or may be interested in applying for funding for fencing, revegetation or surface drainage, we would like to hear from you. Comments can be directed to:

Kevin Hopkinson Wetland Project Officer PO Box 525 Albany WA 6330 Ph :98410114 Fax :98421204 Email : [email protected]

3 Table of Contents

1.0 Project background…………………………………………. 1

2.0 Introduction to the Coomalbidgup Swamp Catchment………… 2

3.0 Coomalbidgup Swamp Wetlands –Physical Description………….. 3

4.0 Geological History of the Area……………………………………. 4

5.0 Hydrology of the Coomalbidgup Swamp wetlands…………….. 5

6.0 Significance ………………………………………………… 6

6.1 -Regional …………………………………………… 6 6.2 -local………………………………………………… 6

7.0 Threats-……………………………………………………… 7

7.1 Inundation/waterlogging……………………………. 7 7.2 Salinity……………………………………… 8 7.3 Eutrophication/sedimentation ……………………… 8 7.4 Grazing……………………………………………… 9 7.5 Feral Animals……………………………………….. 9 7.6 Weeds ………………………………………………. 9

8.0 Catchment management recommendations…………………. 10

Action Plan…………………………………………. 11

Wetland Monitoring………………………………… 12

9.0 Conclusion……………………………………………………. 14

References…………………………………………………… 15

Appendices

Appendix 1 Location map

Appendix 2 Map of wetlands in Coomalbidgup Swamp Catchment

Appendix 3 Wetland aerial and ground photographs 2002

Appendix 4 Hydrograph of groundwater bores

Appendix 5 Potential Corridor Projects

4 Catchment Management of the Coomalbidgup Swamp Wetlands Esperance, South Coast Region of WA.

1.0 Summary and Project Background

The Water and Rivers Commission (WRC) is currently developing a regional water resources allocation plan for the Esperance ground water area. One of the components of this plan is to develop an understanding of the environmental significance of the wetlands of the area through a regional survey.

During 1999, the WRC initiated a regional survey and evaluation of the wetlands of the entire South Coast Region between Walpole and Esperance. The survey for the Esperance region was conducted by Ecologia Environmental Consultants and the last draft of the report was released in November, 1999.

The objectives of the report were to: • Identify regionally significant wetlands • Assign management categories and describe environmental values of these wetlands • Identify high priority wetlands and describe threatening processes and appropriate management action • Promote protection and enhancement of these wetlands. (Ecologia, 1999)

The regional survey and evaluation of wetlands is part of a broader wetland conservation project being undertaken by the Water and Rivers Commission and community group Green Skills.

The aim of the project is to focus on catchment areas within suites of significant or outstanding wetlands that have been identified in the survey by Ecologia (1999), and assisting those communities to develop and implement wetland management plans that integrate into existing catchment activities.

The Coomalbidgup Swamp catchment was targeted due to the wetlands of the area being: 1. Locally outstanding, 2. Threatened or at risk, and 3. The opportunity available to work with an active community and other agencies (Agriculture WA and CALM) to incorporate wetland management into farm and catchment planning activities.

NHT funding has been secured to provide limited on ground support for wetland fencing, revegetation and strategic earthworks. Further funding for additional works may be applied for during 2003 under the South Coast Regional Initiative Planning Team (SCRIPT) regional NHT project ‘Southern Incentives’.

This report documents the significant wetlands of the project area, explains the threatening processes that place these wetlands at risk of degradation, and includes management recommendations where appropriate. Details of future potential water management, revegetation and fencing demonstration projects are included, to provide an example of wetland and riparian rehabilitation for other landholders to follow (Section 8.0+Appendix 5).

5 2.0 Introduction

The study area for this report is located approximately 60km to the west of Esperance, on the eastern south coast of WA (Appendix 1).

Climate The area experiences a Mediterranean climate with cool wet winters and warm to hot, dry summers. Annual rainfall is approximately 620mm at Esperance, with 410mm at Scaddan, 50km to the north. Summer rainfall is infrequent but can be substantial as a result of summer thunderstorm activity and the remnants of tropical cyclones. Annual pan evaporation is 1600mm. Monthly pan evaporation is less than rainfall 7 months of the year (Ecologia 1999).

Land Use Land use ranges from sheep grazing and cropping to cattle grazing and timber plantations closer to the coast. Pre 1995 the dominant tree species planted for timber were maritime pines (Pinus pinaster). Since the mid to late 90’s, increasing areas of the higher rainfall area have been planted to Tasmanian bluegum (Eucalyptus globulus) plantations.

Report Focus The focus area of this report is the catchment of Coomalbidgup Swamp and the associated wetlands. These include (named after the property owners): • ELD swamp south • Mutchs swamp north • Mutchs/Lanes swamp

Management of these wetlands will depend upon a number of catchment based measures:

• Protection of creeks, watercourses and drains and other wetlands on private property through fencing, exclusion of stock and control of feral animals. • Establishment of a vegetated buffer along watercourses to filter surface runoff and remove sediments and nutrients. • Rehabilitation of degraded sites through revegetation with native species. • Implementation of catchment activities that will stabilise the hydrology of the catchment and restore the water balance of the wetlands such as using surface water drainage, perennial fodder and pastures and commercial timber plantations.

6 3.0 Coomalbidgup Swamp Wetlands -physical description

Size The Coomalbidgup swamp is contained within a Shire reserve approximately 200ha in area. This reserve provides an excellent fringing buffer of a diverse range of vegetation that surrounds the wetland with a variety of important habitats.

The other large wetlands listed in addition to the Coomalbidgup Swamp are either part of an internally drained catchment (Mutchs and Mutchs/Lanes) or a catchment linked to the Coomalbidgup Creek (ELD South Swamp-Refer Figure 1). They are all located within 4 km of the Coomalbidgup Swamp. Mutchs North swamp covers approx 40ha, Mutchs/lanes swamp covers approx 60ha, and ELD south swamp covers approx. 30ha

Type All basin wetlands within the Coomalbidgup Creek catchments were once seasonal sumplands. (Ecologia, 1999). They supported dense stands of trees that were subjected to periods of inundation and drying as the wetland filled and dried. Catchment clearing and high rainfall years in the late 1980’s have changed the hydrological cycle of these wetlands, so they are now near permanent waterbodies – ie lakes, though the smaller basins at ELD South and Mutchs North may still dry out.

This increased inundation has led to the death of most of the wetland basin vegetation. Mutchs North swamp is covered in dead paperbarks, Melaleuca cuticularis. The other 3 swamps are covered in yate Eucalyptus occidentalis, with some paperbark on the fringes.

Mutchs/Lanes swamp and Coomalbidgup appear physically similar, they are both located within deep basins, and fringed by a sandy ridge on the south eastern shores. Formation history of these wetlands appears to be different however, with Ecologia (1999) classifying the wetlands into separate suites.

Wetland Suite Characteristics ELD swamp Sears rd suite Sumplands/damplands formed on the Esperance land system Mutchs North Swamp Ashdale suite Sumplands formed within Quaternary aeolian dunes Mutchs/Lanes swamp Ashdale suite Sumplands formed within Quaternary aeolian dunes Coomalbidgup swamp Coomalbidgup swamp suite Basin formed at interface of ocean shoreline sands and Pallinup siltstone.

Landscape The Coomalbidgup creek wetlands have formed on the undulating plain of the Esperance Land system. This land system is characterised by a surface layer of sand greater than 80cm deep overlying a thick layer of clay (Komarzynski, 2000). The clay layer then overlies the Pallinup sediments of the Plantagenet group.

Water Quality

The Coomalbidgup wetlands vary from being brackish to saline in the lakes, depending upon the time of year and season. Water quality is linked very closely with the runoff from the catchment and creek lines. Salinity levels have increased over recent years due to evaporation of lake water and concentration of salts.

7 Wetland Salinity-electrical Salinity- Salinity-grains per conductivity (ms/m) parts per million (ppm) gallon (gr/gal) ELD swamp 1100 6050 424 MutchsNorth Swamp 2000 11000 770 Mutchs/Lanes swamp 760 4180 304 Coomalbidgup swamp 960 5280 384

In addition to increasing salinity, there is potential for excessive nutrients that have been washed into the wetlands, to trigger algal blooms that will degrade water quality further.

Minor algal blooms have been observed in recent summers in Coomalbidgup swamp as a result of nutrient enriched sediments being transported in creek runoff from the catchment. This highlights the significance of the creek contributions to the health of the wetlands.

Vegetation The fringing buffer vegetation of the Coomalbidgup swamp reserve has been well surveyed by the Esperance Wildflower Society, in a study performed on behalf of the Coobidge Landcare Group (1998).

Six distinct plant communities were recorded, with species including Banksia speciosa (showy banksia), Lambertia inermis (chittick), Alyogyne huegelii (native hibiscus) and Eucalyptus occidentalis (swamp yate). In total 161 species were listed, including 18 weed species.

The remaining wetlands have poor fringes of vegetation, with only yate and paperbark trees and seedlings surviving. Removal of stock from the portion of Mutchs/Lanes wetland on Lanes property has seen an excellent regeneration of seedlings where high water levels have receded over recent years. The fenced wetland on ELD south also has some promising regeneration present, with some upland species including Acacia cyclops returning.

Catchment Area The Coomalbidgup swamp is fed by an intermittent creek that flows from a catchment of approximately 9700ha. Over 90% of the catchment was cleared between 1964-1972.(Froend and van der Moezel 1994). ELD south receives surface run off from the 2 properties to the north, Mutchs North has a small but significant creek feeding from the north, and Mutchs/Lanes is fed by overflow from Mutchs North, and also via 2 gullies draining land to the north east and west.

Corridors At present there is a patchy corridor of vegetation along the creek flowing into Coomalbidgup swamp. The main channel of the creek is around 9km in length, and the riparian fringe of the creek appears to be up to 50% vegetated, located in 3 main blocks. This creek has suffered severe erosion following the wet winter of 1989 and subsequent summer floods, with widespread loss of deep sands obvious in poorly vegetated sections. There is potential to create corridors from ELD south and Mutchs/Lanes by fencing and revegetating drainage lines feeding these swamps. Refer to the management recommendations that follow (Also Appendix 5).

8 4.0 Geological history of the Area

The southern portion of Western Australia is underlain by basement rock from two geological units-the Yilgarn Craton and the Albany Fraser Oregon.

The boundary between these two formations is not well defined east of Ravensthorpe, however it would appear the area of this study is underlain by the younger Albany –Fraser formation (Ecologia 1999).

Antarctica began to break away from Australia 135 million years ago resulting in the sagging of the continental shelf area. Fluctuating sea levels over the following 60 million years resulted in the deposition of material that formed the Bremer Basin. This basin extends right along the South Coast and well offshore into the present sea bed.

The tertiary sediments that have since filled the Bremer basin region consist of sands overlying material known as the Plantagenet group. This group consists of material from two origins – the lower laying Werillup formation and the overlying Pallinup siltstone

The Werillup formation consists of dark clays, coarse sands, siltstone, lignite (coal) and sandstones and has infilled low lying drainage depressions and channels in the underlying ancient bedrock.

The Pallinup siltstone was formed during a shallow marine environment and consists of siltstones, sandstones and spongolite.

The Pallinup siltstone sits higher in the landscape and may overly either the Werrilup formation or lay directly over the basement bedrock.

About 30 million years ago the Darling Plateau began to be uplifted, resulting in the Southern Coastline tilting towards the south and forming the extensive Ravensthorpe Ramp. The tilting of the ramp initiated the southward drainage that is seen in the near coastal region today. Eroded coastal sediments were transported inland to form sand sheets and dunes. Continued wind and wave action during the last geological period up to 2 million years ago has led to deposition of coastal sand dunes and development of the inland sandplain. (Short 2002, Keen 1992).

Wind blowing across the sandplain has scoured surface sand from these depressions and other flat lying terrain, enhancing the basins and exposing clays and forming claypans common to much of the sandplain area.

9 5.0 Hydrology of the Coomalbidgup swamp wetlands

Water movement through the catchment depends on the gradient of the land surface and the underlying bedrock, the hydraulic conductivity (the ability for water to travel through a soil) of the landform and the ability of the soil to store water.

The Coomalbidgup swamp wetland group has formed on the Esperance Sandplain over a deep profile of sediments that overly the regional bedrock. This zone of material overlying the bedrock is referred to as the regolith. Simons (2000) compares the regolith to a sponge sitting on a solid block of concrete (ie basement rock).

Soils of the Esperance land system are known as duplex soils, where a layer of sand overlays a thicker layer of clay. The upper (A) horizon allows easy infiltration of water which is perched above the more impermeable clay layer. This horizon can fill quickly and cause waterlogging and associated problems (Ecologia, 1999).

Relationship between the wetlands and the regional groundwater is unclear. In the original pre clearing state, these wetlands would have been perched above the deeper groundwater and were reflections of ponded water that resulted from creek inflow.

Higher salinities in parts of the catchment may be related to bedrock highs, that interrupt the flow of deeper groundwater and bring this to the surface. This could be responsible for the elevated salt concentrations in the Mutchs north swamp, which sits higher in the landscape than Mutchs/Lanes swamp. It is possible a bedrock high is south of this wetland, between this swamp and Mutchs/Lanes.

Mutchs/North and Mutchs/Lanes have been classified as being of the same suite, however it is obvious from field visits that they are quite different in a number of areas including hydrology, vegetation and landscape setting. Interestingly, these systems are connected by surface flow when Mutchs north overflows. This overflow path has been enhanced in recent years with a broad shallow drain to guide the flow path when Mutchs north overflows. Mutchs/lanes is in a deep basin that would require an enormous amount of water to fill and overflow. As one local recently quoted when asked if this wetland would overflow –“if this lake ever fills, then the whole area is in a lot of trouble!”

Drilling close to the wetlands is needed to fully understand the relationship of the wetlands to the regional groundwater. For instance, a single bore hole has been drilled in the south west corner of the Coomalbidgup swamp reserve. This water level in this bore (COO10b) is 10- 11m below ground. (Appendix 4). Of interest, is a nearby borehole (AG24) which would only be 500m from the Coomalbidgup bore, has ground water some 2m closer to the surface.

This may indicate that the groundwater follows a similar contour to the level at the surface, which may be a result of the gradient of the underlying bedrock. Further drilling in the area would indicate if there is a bedrock high to the west, or if the bedrock deepens heading back towards the Lort River.

The Department of Agriculture have received funds through this project to drill another bore in the north eastern corner during 2003, and possibly conduct a bathometric survey of the bottom of the lake across a line between these two bores. This will give a clearer picture of the gradient of the water table beneath the lake, and how deep the bottom of the lake is with relation to the surface of the ground water. This will then help guide future management decisions.

10 6.0 Significance of the Coomalbidgup Swamp wetlands

6.1 Regional Significance

Following the regional evaluation of wetlands, the Coomalbidgup Swamp has been identified as being regionally significant due to a number of features. These features range from: • the size and type of the wetland, • the landscape setting, and • the refuge the wetland provides to waterbirds.

In particular, the size of the wetland and associated vegetation and the reasonable water quality ensures the area is a significant refuge for flora and fauna and so regionally important habitat in the mainly cleared agricultural landscape surrounding the reserve.

The Coomalbidgup swamp has been regularly monitored and surveyed by CALM and Birds Australia between 1981-1991, due to the large number of water birds that roost, nest and moult in the area. The wetlands have also been surveyed as part of the CALM waterfowl counts conducted annually in South Western Australia during 1988-1992.

During the most recent waterfowl counts, 59 individuals were counted representing 9 different species of waterbirds. In addition, a survey of the birds within the reserve fringing Coomalbidgup Swamp identified 36 different species, including breeding pairs of Eurasian Coots.

6.2 Local Significance

The wetlands are significant on a local scale for a variety of reasons. All the wetlands provide differing levels of refuge for fauna, in particular waterbirds, often being the only surface water in the surrounding landscape (with the exception of farm dams).

The large reserve at Coomalbidgup swamp provides an easily accessible area for bird watchers and wildflower enthusiasts. The South Coast highway passes along the southern boundary of the swamp reserve, with an access track from the highway down to the high water mark. Access to the lake is limited. There is a dense fringe of yate and paperbark seedlings that have germinated on the high water mark, with the only cleared path to the water a car width track from the highway access.

The area is a prime spot for highway travellers to have a break from driving, unfortunately there is no signage to indicate that the site is there. Negotiations are currently underway between the Shire of Esperance, Main Roads WA and Green Skills (on behalf of the Coobidge Landcare Group) to improve amenities. This includes road signage, and an interpretive sign/shelter in the car park to provide some basic information about the lake, and possibly the birds and plants of the area.

The open water of the wetland is also choked with vegetation, the dead trunks of yates that covered the basin preventing activities like boating but perhaps creating opportunities for more passive water craft like canoes. Some of the dead yates have fallen over, but large stands still remain. They are important to retain as many of the trees appear to have hollows and so provide nesting sites for birds. Human interference in the remainder of the lake is considered minimal.

11 7.0 Threats to the Coomalbidgup Swamp wetlands

Wetlands and waterways in southern Western Australia are under threat from changing water quality and degradation of fringing vegetation. Changes to water quality have occurred through increasing salinity, eutrophication and sedimentation. These changes are directly attributable to catchment clearing (Schofield, 1989).

Removal of native vegetation through clearing results in changes to the groundwater regime, with less groundwater being utilised through deep rooted vegetation, and more surface runoff discharging into waterways. This increase in catchment water has further degraded wetland vegetation through waterlogging.

Rising groundwater and associated waterlogging and salinisation, combined with grazing by introduced animals, is responsible for much of the decline in vegetation seen in wetlands and waterways across southern Western Australia (Olsen & Skitmore, 1991).

There are a broad range of these processes that likewise threaten the wetlands of the Coomalbidgup Swamp catchment.

7.1 Inundation/waterlogging

Increased runoff through catchment clearing has meant more water is flowing from the catchment, particularly after high rainfall events.

With internally drained catchments such as the Coomalbidgup swamp wetlands, a threat exists to the health of the wetlands from water quantity as well as water quality. Pen (1997) cites wetland drowning through prolonged flooding as a problem that is particularly pertinent for internally drained wetland systems.

The flooding responsible for the tree decline in the lakes is from events in the late 1980’s. Coomalbidgup swamp filled during the winter of 1986, and received another wet year in 1989. The swamp then became a lake and has not been dry since. Field observations in 1990 showed the lake to be up to 5m deep at this time (Froend and van der Moezel, 1994).

Another threat to the ecological function of the wetland is from loss of diversity fringing vegetation. Froend and van der Moezel ( 1994) have shown that upland vegetation communities were the first casualties of high water levels after 1989. Recruitment of the shoreline that was exposed as water levels receded has mainly been from wetland species such as yate and paperbark, and a variety of weed species. The upland areas have obviously diminished due to the prolonged and extreme flooding, and have probably been permanently lost from this zone.

7.2 Salinity

The Coomalbidgup swamp wetlands were fresh up to very recent years (with the exception of Mutchs north swamp), with increases in salinity mainly due to evapoconcentration of waters held within the lakes. Water quality results from 1994 show salinity at Coomalbidgup as being brackish, below 800ms/m (Froend and van der Moezel, 1994). Recent testing has levels in excess of 1000ms/m, which classifies the lake as being saline.

There is currently little secondary salinity in the catchment, though subsoil salt stores are large and there is evidence that groundwater in the catchment are rising. Continued rise of groundwater will see the salinisation of low lying areas of the catchment and the transport of these salts into the wetland basins (Froend and van der Moezel, 1994).

There is a real threat to the ecological function of the wetlands from steadily rising water table levels if the upper catchment becomes increasingly saline. Salinity and waterlogging combine to synergistically act together and cause more stress to plants than either factor on its own (Pen, 1997).

12 The rises in catchment salinity that may occur in future years are of concern and indicate that significant catchment based works are required to utilise more of the rainfall that hits the ground in an effort to stabilise and lower ground water levels.

7.3 Eutrophication and sedimentation

Observations made in recent years indicate that Coomalbidgup Swamp may have been subject to algal blooms at certain times during summer. This indicates the wetlands have become nutrient enriched, receiving an input of phosphorous, nitrogen and organic material from catchment runoff.

The loss of fringing vegetation along waterways together with increased run off from catchment clearing results in the transport of nutrient rich sediments (Olsen & Skitmore, 1991) which consequently flow into the wetlands.

Nutrients in the form of nitrogen, phosphorous and organic matter may be washed down the catchment in concentration after a summer storm or high rainfall event. Some nitrogen and phosphorous may be taken up by biological processes, however most will settle into the sediments of the lake.

Inorganic or dissolved phosphorous is bonded (adsorbs) to soil particles and is readily transported with mobilised sediment (George et al 1996).

Inorganic or dissolved nitrogen occurs as ammonium, nitrate and nitrite. Ammonium adsorbs to soil particles, but is slowly oxidised to nitrite. Both nitrate and nitrite are highly soluble and easily transported by water (George et al 1996).

Organic matter is broken down and decayed by microbial activity. If large quantities of organic matter are present, the decomposition process will dramatically reduce dissolved oxygen levels in the water, making conditions unsuitable for most aquatic fauna. Low concentrations of oxygen in the water will then trigger the release of nutrients previously stored in the sediments which may cause algal blooms.

Algal blooms are dependent on a combination of the right conditions of nutrient availability, temperature, and light. During summer, physical conditions for blooms become suitable and so rely upon suitable levels of nutrients being available.

Algal blooms have harmful effects on aquatic flora and fauna. Plants will suffer from shading and reduced light penetration. Some algae contain toxins that harm fish and water birds. The blooms also utilise large amounts of oxygen from the water, both during night time respiration and as they decompose after the bloom collapses.

Sediment build up in wetlands can also physically threaten wetland function. As wetland basins fill with sediment they become shallower and so flood further and further outwards, effectively drowning fringing vegetation.

7.4 Grazing by livestock

The Coomalbidgup Swamp reserve is fenced to prevent stock access, so grazing by livestock is not a threat to the wetland vegetation. Fencing of Mutchs north and the northern section of Mutchs/Lanes are priority actions to prevent further decline of the remaining fringing vegetation by stock.

13 7.5 Feral Animals

The isolated nature of the wetlands and surrounding vegetation in an otherwise largely cleared catchment means they are refuge sites for all fauna, including notable waterbirds and feral animals such as foxes and rabbits.

Foxes are a concern because they can predate heavily on breeding birds that nest amongst the wetland vegetation. The wetlands support threatened species such as Freckled Duck (Jaensch, 1992). Control of these predators is vital to preserve the conservation value of the wetlands.

Rabbits can cause disturbance through digging warrens and grazing on native vegetation, particularly young seedlings. This can impinge on the ability of vegetation to regenerate after flooding or fire, and places native fauna under stress through added competition for food. The grazing and diggings of rabbits can instigate erosion on fragile sandy areas. Rabbit control is essential in these remnant areas to prevent population explosions that will devastate the area.

Sandy ridges traverse the lower catchment area and provide excellent areas for rabbits to establish large warren complexes. This is particularly the case in areas that have not been cleared and not disturbed by farming activities. Where warrens are difficult to locate and access, individual bait stations may be the most effective method of controlling rabbits to any degree (Parry pers comm).

7.6 Weeds

Weeds can threaten the habitat value of a wetland by out competing native vegetation, affecting nutrient recycling, increasing fire risk, and inhibiting regeneration of natives, particularly after a disturbance such as fire or stock grazing. Fencing from stock is an effective way of reducing weed invasion. Sheep and cattle can transport weed seeds, denude native vegetation, and provide disturbed environments ideal for the establishment of fast growing weeds. (Hussey et al, 1997)

In general, the Coomalbidgup swamp has an excellent fenced buffer of native vegetation that is restricting the penetration of weeds and grasses. The area where weed invasion is a problem appears to be on the lake shore line that becomes exposed as the water levels recede. Weeds quickly colonise this bare damp ground and will flourish and outcompete native plants, until the next flood event drowns them.

The creeks feeding the lakes are a potential source of weeds, particularly if perennials such as kikuyu becomes established in the upper catchment. Whilst this perennial does have important water use and stabilisation capabilities, it can easily spread by seed and runners so care must be taken to ensure it does not spread down the creeks.

14 8.0 Catchment Management Recommendations

The protection and enhancement of waterways of the Coomalbidgup Swamp catchment is a priority activity to maintain water quality in the catchment and the downstream lakes. In addition to the protection and enhancement actions on the waterways and wetlands, there are works further out in the catchment in the farm paddock where the processes of recharge, discharge and surface water control will need to be managed.

These works will have positive benefits to both the wetlands and the farms by aiding the movement of water from low lying flats, preventing waterlogging of these areas and minimising recharge to the regional ground water.

Significant planning has already been completed in the catchment in recent years, with the area being a Focus catchment under the State Salinity Action Plan during 1999. Previously, the Coobidge Landcare Group Inc has undertaken several surface water and catchment planning projects since the late 1980’s.

As a result of this activity, reports on catchment management planning, hydrology and wetland response to flooding were completed (Read 1991, Gutteridge et al 1990, Froend and van der Merzel 1991).

Unfortunately a lot of effort from landholders in planning projects in the past has resulted in little on ground action, and currently the group is static with key motivating farmers in the area becoming ‘burnt out’ from the workload involved with coordinating the group. This, combined with consecutive summer floods in the area, has resulted in the group not spending past NHT funding with the result that funds have had to be returned unspent.

There is however some important protection and rehabilitation work continuing by individual farmers in the catchment and these works need to be supported with continued funding and planning assistance.

Future Catchment Management

Given that excess catchment water is the major process threatening the Coomalbidgup Swamp wetland systems, the most effective management option is to manage and utilise some of this water by retaining as much as possible in the upper catchment areas.

Surface water management options recommended in the reports produced for the catchment include utilising degraded wetlands as retention basins. This could also be extended to clay flats areas which are bare and unproductive, as ponds could be created by pushing earth bunds up and creating small dams.

This strategy would appear to be an effective way of holding excess water in the catchment, but would depend upon the following factors: • The wetland was not going to be degraded from holding excess water, ie existing vegetation (if any ) was not going to be drowned. Also a good understanding of the wetland hydrology and base sediments would be needed to ensure the regional groundwater would not be recharged. • Suitable surface water drainage ie shallow ‘w’ drains were installed to direct flow into these basins. • Protected overflow areas were in place to deal with high run off events and minimise possible erosion damage.

Possible benefits from holding water back from entering the Coomalbidgup Swamp include : • Creating a supply of fresh water in upper catchment areas for stock use, possible aquaculture or summer crop irrigation. • Reduce water volume and sedimentation in receiving wetlands. • Minimise ground water recharge.

15 On farm problems of scalding/waterlogging, erosion and topsoil loss, and feed/water shortages can be helped by diversifying farm activities and incorporating water management measures into the farm operation. Other options include: • perennial vegetation (tagasaste/lucerne and kikuyu), • rehabilitation bare salt affected ground with salt tolerant plants such as fodder saltbush, • alleys of trees for fodder or on farm timber, • contour banks and shallow drains to enhance water movement and dams/ponds/wetlands for harvesting.

Detailed farm water management is beyond the scope of this report and further advice should be sought from specialists such as catchment support staff and hydrologists from Agriculture WA.

Action Plan for the catchment

Specific recommendations relating to catchment works on individual properties is presented in the Action Plan table that follows (Table 1+Appendix 5). The table summarises potential projects that will have a positive benefit to both the properties concerned, and downstream on the watercourses and wetlands of the catchment.

A priority activity is to establish the groundwater depth, flow path and relationship with Coomalbidgup Swamp, through the drilling of a further piezometer and conducting a survey of the Lake. Funding has been provided to Dept Agriculture staff to commence autumn 2003.

A proposal to investigate once this work is completed is to survey the lowest lying point of the basin rim surrounding Coomalbidgup Swamp to determine if it is feasible to construct an overflow point for the wetland. The plan would be to run this overflow into the Coomalbidgup west creek, for disposal into the Barker Inlet.

The point would need to be low enough so as to provide a reduced high water mark in the swamp, to preserve the belt of fringing vegetation that is establishing in this zone. This would ensure that no further loss of this fringing vegetation occurs, recognising that there is no chance of establishing trees across the bottom of the lake again.

The overflow would reduce maximum water levels in the lake, allow flushing to prevent salts concentrating, with outflow occurring at a controlled rate to ensure no interference with downstream watercourses.

This proposal could be modelled on a similar project that was funded during 2001 at Chillinup Lake in South Stirlings, where 1500m of 200mm pipe was laid through a sand dune to provide an overflow point for the lake to prevent loss of valuable fringing vegetation.

Obviously this proposal would need approval from downstream landholders and stakeholders such as Esperance Shire and Main Roads.

The other recommended priority actions can be part or fully funded immediately if landholders are interested in completing works during 2003. Fencing grants and native seedlings are available, with funding for drains also possible, but this may depend upon all parties along the watercourse being involved. Drainage plans in isolation may not be eligible for funding.

Funding is currently available to assist landholders with fencing of watercourses at a rate of $600 per km. There is also assistance available to help revegetate these fringing areas, with native seedlings provided for areas that can be ripped and sprayed by landholders. Applications can be made by simply providing a location map of the property detailing the areas for proposed fencing/revegetation. For further information, refer to the contact details in the front of this report.

16 Wetland Monitoring

A comprehensive regional wetland monitoring program has been established by the Water and Rivers Commission to sample 30 high value wetlands from across the South Coast region, including 3 sites in the Esperance area.

This program samples a range of water quality parameters and macroinvertebrate populations, to establish a base set of data for the condition of these high priority sites. This will enable early detection to changes in water quality that may result through catchment based activities.

The program focuses on sites that are on privately owned land, and includes sampling the Coomalbidgup Swamp. Currently water quality measurements are recorded twice yearly, in spring and autumn. This data is recorded on a database held by the water and Rivers Commission and is readily available to any individuals or groups. Refer to the contact details in the front of this report.

17 Action Plan – Coomalbidgup Swamp catchment

Loc Description Works Required Priority No 1559- North eastern fringe of Drill piezometer to determine High-funded 1553 Coomalbidgup Swamp depth to groundwater for Autumn 2003 1554 Upper reach of broad flat area that Install scraper/spoon/’w’ drain to High drains southward better define low lying flat and aid –Funding water movement off site. Fence may be drain and revegetate to create available to windbreak/corridor assist. 1555 Mid reaches of low lying flats. As above. High-as above 1571 Low reaches of flat, terminating in As above. High-as wetland in adjoining property. above 765 ELD South Swamp Construct broad spillway for drain High to enter wetland basin. Excavate and construct overflow point-possibly by installing 100- 200mm pipe to slow release peak levels in wetland basin. 1571 Drainage line from wetland basin Enhance drainage, fence and High into defined waterway on southern revegetate as per shallow drains blocks (Coomalbidgup west creek) above. waterlogging and direct fresh water Construct armoured spillway to into wetland. receive overflow from wetland. 1551 Broad gently sloping flat area Install scraper/spoon/’w’ drain to Medium drains into Mutchs/lanes swamp. better define low lying flat and aid water movement off site. Fence drain and revegetate to create windbreak/corridor 1551 Northern half of Mutchs/Lanes Fence this fringe of the wetland to High-funding swamp prevent stock access. currently Revegetate area within fence to available to establish buffer between fence assist. and existing wetland vegetation. 1552 Mid reaches of Coomalbidgup This section of creek has patchy Medium- creek remnant vegetation-revegetate to seedlings link existing blocks of trees. available to plant. 1550 Upper reaches of Coomalbidgup Little remaining vegetation along High creek this section of watercourse. Fencing Revegetate and protect creek and assistance fringing vegetation from stock. and seedlings available 1/3488 Headwaters of Coomalbidgup Little remaining vegetation along High 0 Creek this section of watercourse. Fencing Revegetate and protect creek and assistance fringing vegetation from stock. and seedlings available

18 9.0 Conclusion

This report has brought together information about the Coomalbidgup Swamp wetlands that will help to raise local awareness to the value and significance of these unique wetlands and aid in the future management of these sites.

Significant works have already been undertaken by some landholders in the area towards fencing and rehabilitating the catchments of these valuable wetlands.

Ongoing enhancement of these protected waterway areas is necessary to ensure the corridor of vegetation is continuous and of sufficient density to filter surface runoff from adjoining farmland. Importantly, there is little vegetation existing amongst much of these upper catchment blocks, so this is a great opportunity to establish a belt of vegetation to act as a corridor for birds to move along, and provide wind shelter for stock.

In addition to the watercourse protection work, another priority area for management lays with utilising the water that falls on the surrounding farmland.

Increasing water usage in the upper catchment areas will have downstream benefits by reducing volumes of water that flow into the creeks and the potential pollutants (salt, sediment, nutrients) that are transported.

The full suite of alternatives needs exploring with advice from qualified officers such as Department of Agriculture staff. The best opportunity for this lays with the farmers in the catchment coming together and once again working as a group and making decisions based on the needs of the whole catchment.

The Coobidge Landcare Group has instigated most of the land management planning that has occurred over recent years. It is recognised that much effort has gone into previous work, with at times limited outcomes. This has resulted in burn out by some landholders who are no longer willing to spend time working with the group on a catchment scale. It is hoped that some interest for new projects such as catchment surface water management options may revive the group.

If the community can work and plan together as a catchment, the benefits of any activities will be enhanced so that both the farms and the wetlands at the bottom of the catchment are winners. By working together the landholders will aid the long term sustainability of their farms and ensure protection of the important Coomalbidgup Swamp wetlands long into the future.

19 References

BOM (Bureau of Meteorology) 1998 “Wind Frequency Analyses and Wind Roses for Albany Town and Albany Airport”. National Climate Centre, Bureau of Meteorology, Melbourne.

Department of Conservation and Land Management. 1999 “ Esperance Lakes Nature Reserves Management Plan”, National parks and conservation Authority, Perth, WA.

Ecologia Environmental Consultants 1999 “ A Preliminary Evaluation of Wetlands in the Esperance Water Resource Region”

Froend, RH & van der Moezel, PG 1994 “The Impact of Prolonged Flooding on the Vegetation of Coomalbidgup Swamp”, in Journal of the Royal Society of Western Australia, 77:15-22, 1994.

Froend, RH & van der Moezel, PG 1991 “Wetlands of the Coobidge Creek Catchment, their classification and response to prolonged flooding”.

Gee, ST & Simons, JA. 1997 “Catchments of the Esperance Region of Western Australia, Resource Management Technical Report 165, Agriculture Western Australia, Esperance.

George,R. et al 1996 “Environmental Water Quality – A Guide to Sampling and Measurement” Agriculture Western Australia, Miscellaneous publication 16/96 Issn 1326-4168.

Gutteridge Haskins & Davey Pty Ltd 1990 “Dept of Agriculture Esperance Land Conservation District Coobidge Creek Catchment Group : Drainage.

Ferdowsian, R. et al. 1996 “Wetlands on tertiary Sandplains need to be managed to Reduce Secondary Salinity” Agriculture Western Australia, 444 Albany Highway Albany, WA 6330.

Ferdowsian, R. 2000 Personal Communication, Agriculture Western Australia, 444 Albany Highway Albany, WA 6330.

Hussey,B.M.J. Keighery,G.J. Cousins,R.D. Dodd,J. Lloyd,S.G. 1997 “ Western Weeds: A guide to the weeds of Western Australia”, The Plant Protection Society of Western Australia (Inc.), Victoria Park, WA, 6100.

Komarzynski, R 2000 “Surface and subsurface water management” in ‘Dalyup-State of the Catchment 2000’, AgWest Esperance publication.

Olsen, G & Skitmore, E. 1991 “State of the Rivers of the South West Drainage Division”, Western Australian Water Resources Council Publication No 2/91

Parry,C 2000 Personal Communication, Agriculture Protection Board, Agriculture Western Australia, 444 Albany Highway Albany, WA 6330.

Pen, L. 1997 “A Systematic Overview of Environmental Values of the Wetlands, Rivers and Estuaries of the Busselton – Walpole Region”, Water and Rivers Commission, Water Resource and Planning Series, Report No WRAP 7.

20 Pen,L. 1999 “Managing Our Rivers”, Water and Rivers Commission, 3 Plain St East Perth, WA 6004.

Read, VT 1991 “Catchment Planning for the Coobidge Landcare Group”. Rural Planning, Land Management Consultant

Schofield, N.J. 1989 “Stream Salinity and its Reclamation in South-West Western Australia”, Water Authority of Western Australia Report No WS 52

Short, R. 2000 A conceptual hydrogeological model for the Lake Warden Recovery catchments Esperance, Western Australia,Resource Management Technical Report 200, Agriculture Western Australia.

Simons, J. 2000 “Hydrogeology” in ‘Dalyup-State of the Catchment 2000’, AgWest Esperance publication.

Spencer, D 2000 Personal communication, Esperance Shire.

21 Appendix 1

Location Map of

Coomalbidgup Swamp wetlands

22 Appendix 2

Map of Wetlands in the Coomalbidgup Swamp catchment

23 Appendix 3

Wetland Aerial and Ground photographs, 2002

24 Appendix 4

Map and Hydrograph of Coomalbidgup Swamp Groundwater Bores

25 Appendix 5

Potential corridor projects

26