Conservation at Esperance WA

Recommendations for the Management of the Lake Gore and Coobidge Creek

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

by Wetland project officer Kevin Hopkinson

December 2001

1 Table of Contents

1.0 Summary and Project background

2.0 Introduction

3.0 Lake Gore and Coobidge Creek Wetlands -physical description

4.0 Geological history of the Area

5.0 Hydrology of the Lake Gore and Coobidge Creek wetlands

6.0 Significance of the Lake Gore and Coobidge Creek wetlands

6.1 - Regional and National Significance 6.2 - Local Significance

7.0 Threats to the Lake Gore and Coobidge wetlands

7.1 Eutrophication and sedimentation 7.2 Inundation/waterlogging 7.3 Salinity 7.4 Grazing by livestock 7.5 Feral Animals 7.6 Weeds

8.0 Catchment Management Recommendations

9.0 Conclusion

Appendices

Appendix 1 Location Map of Coobidge Creek and Lake Gore wetlands

Appendix 2 Map of Revegetation and fencing projects 2002

Appendix 3 Wetland Aerial and Ground photographs, 2001

Appendix 4 Coobidge Creek Foreshore Survey

2 Recommendations for the Management of the Lake Gore and Coobidge Creek 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 Lake Gore wetlands/Coobidge Creek catchment was targeted due to the wetlands of the area being: 1. Locally outstanding, nationally and internationally significant, 2. Threatened or at risk, and 3. The opportunity available to work with the community and other agencies (Agriculture WAand 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. The project also includes a regional wetland monitoring program and an education component aimed at raising community awareness to the values and threats to South Coast wetlands.

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 revegetation and fencing demonstration projects planned during 2002 are included, to provide an example of wetland and riparian rehabilitation for other landholders to follow (Appendix 2).

3 2.0 Introduction

The study area for this report is located approximately 40km 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 study is the catchment and wetlands of Coobidge creek. This system flows into an unnamed swamp near Lake Kubitch, which is linked with nearby lakes Carbul and Gidong by a network of shallow swamps. These lakes are part of the Lake Gore Nature Reserve, which has recently been added to the international list of RAMSAR wetlands.

The wetlands in the Lake Gore nature reserve have been identified as important habitat for a number of waterbirds. This includes migratory species such as Hooded Plover and Banded stilt, and Australasian Shelducks (ANCA 1996).

All nature reserves are vested in the National Parks and Nature Conservation Authority (NPNCA), and are managed on its behalf by the Department of CALM (CALM 1999).

Management of the wetlands in the CALM reserve will depend upon a number of catchment based measures:

• Immediate protection of creeks 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 pastures and commercial timber plantations.

4 3.0 Lake Gore and Coobidge Creek Wetlands -physical description

Size The Lake Gore Nature reserve is approximately 1500ha in area, including the larger Lake Gore (740ha) and Overflow swamp (400ha). The wetlands in the reserve form a system that is connected or linked through a series of marshes, lakes and small creeks and drains. Overflow from Lake Gore and lakes Kubitch, Carbul and Gidong is linked to the coastal Qualillup Lake via the system of wetlands in Overflow swamp. Local farmers believe that in very wet years the coastal chain of wetlands west of Lake Gore link up and flow as far as Barker Inlet, 15km to the west (Baldock, pers comm).

There is a chain of wetlands associated with the mid-upper section of Coobidge Creek contained within a large block of remnant vegetation. This chain of salt lakes appears to have formed in a diagonal line WNW-ESE and is possibly the remnant of a sediment filled ancient watercourse (Simons, pers comm).

Type The Lake Gore wetlands vary in size from mesoscale (approx. 500m-1000m across) to macroscale (1km-10km across), and vary between lakes (permanent water) to sumplands (seasonal).

The Coobidge Creek wetlands are micro-mesoscale sumplands.

Landscape The Lake Gore wetlands have formed on the coastal plain between the coastal limestone and the termination point of southward flowing rivers. The Dalyup River is the main tributary of Lake Gore.

Water Quality

The Lake Gore wetlands vary from being brackish in the swamps, to saline in the lakes, depending upon the time of year and . Despite some fresh groundwater contributions, water quality is linked very closely with the runoff from the catchment and creek lines.

Algal blooms in recent years caused by nutrient enriched sediments from the catchment highlight the significance of the creek contributions to the health of the wetlands.

The Coobidge Creek wetland chain has formed on a sandplain over a deep profile of sediments that overly the regional bedrock. Refer to the following section on formation and hydrology of these wetlands for a full description of these processes.

Vegetation The fringing buffer vegetation of the Lake Gore wetlands borders privately owned property to the north. At this point the reserve is narrow and is only 100m wide in some parts. The reserve is more substantial to the south where there is up to 1km of vegetation running down to the coast.

The dominant vegetation community surrounding the wetlands is fringing woodland of salt paperbark Melaleuca cuticularis, with understorey of coast saw sedge (Gahnia trifida) and samphire in the salt marshes.

5 Catchment Area The Coobidge Creek catchment draining into the wetland system is approximately 20700 ha. Almost 20000 ha of this area is cleared farmland, leaving less than 5% of the catchment with remnant vegetation (Gee & Simons, 1997).

A significant feature of the catchment is the remnant vegetation associated with the chain of salt lakes mid Coobidge Creek. This privately owned vegetation is fenced from stock and covers close to 1000ha and is the major stand of vegetation in the catchment. Also important is the 370ha CALM reserve located at the watershed of the top of the Kateup Creek and the nearby eastern draining catchments.

Corridors Coobidge creek serves as an important corridor between the CALM reserves and the wetlands in the middle of the catchment. It is therefore essential the creek and its fringing vegetation is protected and enhanced to help fauna (and associated flora) move across the catchment.

Fortunately the creek is close to being totally protected with approximately 82% of the main channel protected from stock. Credit must be given to the landholders who have completed this work. Some landholders have completely self funded there fencing projects, whilst others have worked together to secure NHT funding to assist them with the aim of completing the fencing of a significant length of the creek.

4.0 Geological history of the Area

The southern portion of 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.

6 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. (Keen 1992).

Deposits of river borne (alluvial) material at the lower reaches of old rivers such as the Coobidge has formed impermeable layers on the plains at the termination of the southward flowing rivers, where the coastal dunes have formed a barrier between the rivers and the sea. This has led to the creation of extensive areas of wetlands, including the chains of lakes found in the Gore, Mortijinup, and Warden systems (Ecologia 1999).

The chain of lakes in the mid Coobidge catchment have formed over a full tertiary profile, where Werrilup sediments have filled an ancient drainage channel in the granite bedrock, and Pallinup siltstone has been deposited over this. Slumping of material in these sediments have led to the formation of the basins that created the chains of wetlands seen in the area today.

Underground processes and the action of the wind have formed other basin wetlands in the inland sandplain region. Leaching of carbonates in Pallinup siltstones has caused collapsing of sediments and led to localised slumping.

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.

5.0 Hydrology of the Lake Gore and Coobidge Creek 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 upper catchment areas are dominated by soils of the Esperance Land system. (Ecologia, 1999). This land unit is characterised by ancient bedrock overlaid by a zone of weathered bedrock and tertiary sediments. 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).

Most soils of the Esperance Sandplain 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.

7 The coastal wetlands that comprise the Lake Gore system are a reflection of a perched water table that receives flow from three sources:

• Surface runoff from the catchment is received via the waterways that feed the system, in this case the Coobidge creek and Dalyup River. This is the main source of water into these wetlands. • Ground water flowing from the upper catchment towards the coast discharges into the wetlands. This flow may be negligible, however, due to the low hydraulic conductivities of the tertiary sediments containing the groundwater. • Rainfall percolates through the sands of the coastal dunes and recharges the watertable within the dune system. This sandy lens of discharges through the interface with dune and wetland and will seasonally flow into the wetland system.

Water is lost from the wetlands due to:

• Evaporation from summer heat and wind • Evapotranspiration from fringing wetland vegetation • Discharge of wetland into ground water, primarily through the contact with the permeable sands of the coastal dunes.

The wetlands of the Coobidge Creek system reflect a local perched aquifer that is recharged by rainfall and surface runoff from the catchment. Some wetlands occur within the floodplain of the Coobidge creek and also fill when the creek system floods.

These wetlands mainly lose water through evaporation with minimal loss from discharge through base sediments. This means dissolved salts are unable to leave the system, and are concentrated as the wetland evaporates.

Lakes Gore, Gidong and Quallilup are permanent waterbodies, all other waterbodies are seasonal, although may remain inundated for 2-3years following wet . Lake Gore floods at a maximum depth of just over 2m, whilst Quallilup lake near the coast is believed to be up to 5m deep. (ANCA 1996).

6.0 Significance of the Lake Gore and Coobidge Creek wetlands

6.1 Regional and National Significance

Following the regional evaluation of wetlands, the Lake Gore System wetlands have been identified as being both regionally significant and outstanding at a national and international level due to a number of features. These features range from: • the size and type of the wetlands, • the landscape setting to which they belong, and • the refuge they provide to waterbirds.

The Convention on Wetlands of International Importance is an international treaty that aims ‘to halt the worldwide loss of wetlands and to conserve, through wise use and management, those that remain’. The treaty is named after the city of Ramsar in Iran that held the first conference in 1971. The RAMSAR convention provides the framework for worldwide cooperation to support the protection and conservation of important wetland habitats.

8 During 2000, the Lake Gore system was nominated for inclusion onto the International register for wetland protection under the RAMSAR Convention. The listing was recently approved and the site becomes the twelfe Western Australian site listed. The RAMSAR listing does not include the satellite lakes of Carbul, Gidong Kubitch or Quallilup lake, however these wetlands are considered nationally significant and are included as part of the Lake Gore listing in the Directory of Important Wetlands (ANCA 1996).

This international and national recognition underlines the need for protection of these unique wetland systems.

The wetlands in the Lake Gore suite have 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.

A total of 55 species of bird have been recorded in the area, including 18 that are on international treaties. For example:

• The wetlands are the most important known area Hooded Plover Thinornis rubricollis in Australia. Lake Gore supports the largest known population of these waterbirds, with counts totalling over 30% of the global population.

• Lake Gore is also significant for Banded Stilt Cladorhynchus leucocephalus, with counts of up to 20000 individuals, which is 10% of the global population.

• The system is recognised as one of the most important moulting sites for Australian Shelduck Tadorna tadornoides.

Freckled Duck Stictonetta naevosa has been recorded at this site (ANCA 1996).

6.2 Local Significance

The wetlands are significant on a local scale for a variety of reasons. The large nature reserves include remnant vegetation that provides a valuable area of diverse habitat that adds significantly to the area’s fauna and flora refuge qualities.

Access to the lakes is limited. The only obvious tracks enter through private property and there appears to be few breaks in the shoreline vegetation. Human interference in the direct vicinity of the lakes is considered minimal.

Land has been cleared to within 100m of the northern and north eastern boundary of the lakes, however the remnant vegetation surrounding the lakes to the south extends to almost 1km wide.

The vast numbers of waterbirds that visit these wetlands are easily viewed and this makes the wetlands a special area for local bird enthusiasts.

9 7.0 Threats to the Lake Gore and Coobidge 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 Lake Gore and Coobidge creek systems.

7.1 Eutrophication and sedimentation

Observations made by local landholders in recent years indicate that Lake Gore and surrounding lakes have been subject to algal blooms at certain times during summer. This is evidenced by algal mats washed up on the shores of the lakes, particularly at Lake Gore. 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.

10 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. Sedimentation combined with rising water tables are believed responsible for the increased water levels and vegetation decline in Lake Gore (Komarzynski, 2000).

7.2 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 Lake Gore and Coobidge Creek 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 larger lakes of the area have become near permanent due to this excess catchment water. This is believed to have resulted in tree deaths witnessed in several of the lake Gore wetlands (ANCA 1996).

7.3 Salinity

The wetlands of the Lake Gore system are thought to be naturally saline, and some researchers believe that substantial increases in salinity will not occur in the future (ANCA 2000).

Despite this, increases in salinity of the wetlands is still occurring through salts being washed down waterways from salt affected areas higher in the catchment. These upper catchment outbreaks are caused by rising saline ground water bringing dissolved salts to the surface.

The dominant vegetation of the wetlands is saltwater paperbark, Melaleuca cuticularis. Froend (pers comm, 1999) has shown in glass house seedling tests that this species will tolerate wet, poorly drained sites and can withstand salinity levels in excess of 2000mS/m (electrical conductivity). Recent sampling of the water quality of the fringing Lake Gore wetlands showed levels to be 1860ms/m, indicating the fringing vegetation may be close to experiencing levels in the upper limits of tolerance.

There is a real threat to the ecological function of the wetlands from steadily rising water table levels as 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).

The rises in catchment salinity that have taken place in recent 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.

11 7.4 Grazing by livestock

Most of the wetlands of the Coobidge Creek system are fenced to prevent stock access, so grazing by livestock is not a threat to the wetland vegetation. In particular, some of the wetlands have long been protected, and so have buffers of high quality, diverse vegetation surrounding them.

Lake Gore is protected by fencing, however the nearby lakes of Carbul and Gidong have sections of the fringing vegetation presently open to grazing. Lake Kubitch is somewhat more protected by a broad fringe of sedgeland. A fencing program is currently planned by adjoining landowners to totally fence off these important stands of remnant vegetation.

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 Lake Gore and Coobidge Creek wetlands have excellent fenced buffers of native vegetation that is restricting the penetration of weeds and grasses.

The creeks feeding the lakes are a potential source of weeds, particularly if 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.

12 8.0 Catchment Management Recommendations

The wetlands of the Lake Gore and Coobidge Creek systems are reasonably well protected by fencing. Small areas remain around isolated wetlands within the cleared farmland of the catchment, also the north and north east sections around lakes Carbul and Kubitch remain unfenced. Several projects planned for next season will complete some of this work, details of these projects are in appendix 2.

A survey of the foreshore vegetation of Coobidge Creek was conducted to assess the condition of the riparian vegetation, and identify areas that required revegetating or further fencing (Appendix 4). Currently around 82% of the creek is fenced, with further projects planned that will add to this. 4 revegetation projects are also planned with a total of 12800 native seedlings to be planted in the catchment during 2002. Refer appendix 2 for species details.

The protection and enhancement of waterways of the Coobidge Creek is a priority activity to maintain water quality in the catchment and the downstream lakes. Having completed much of this task means the focus must shift to further out in the catchment to the farm paddock where the processes of recharge, discharge and surface water control will need to be managed.

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 significant 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. Some of the work that has been assisted through the Regional Wetland program are summarised in the appendix (2).

Future Catchment Management

Given that excess catchment water is the major process threatening the Lake Gore and Coobidge 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.

13 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 creek system 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 and slow spread of saline scalds in lower catchment and river valley areas.

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). The table summarises projects that are being completed over the next 12 months, as well as suggestions for future projects that will have a positive benefit to both the properties concerned, and downstream on the watercourses and wetlands of the catchment.

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.

14 The program focuses on sites that are on privately owned land, and includes sampling the nearby Coomalbidgup Swamp.

Currently CALM sample the waters of lake Gore twice yearly, as part of the South West wetland database project. This important data will serve as a baseline record that will enable regular comparison to ensure variations in water quality can be detected and possibly correlated to catchment activities.

In addition to this monitoring, a series of groundwater monitoring bores will be drilled in the mid catchment during 2002 to compliment the bores currently monitored by Agriculture WA staff under the Community Bores program.

Action Plan - Coobidge Creek Catchment 2001

Loc Description Works Required Priority No 1 Lower reach of creek that braids Complete fencing to north of High – to be across broad floodplain. Most fringing vegetation surrounding completed vegetation in A grade condition lakes during 2002 1434 Badly eroded section along west Area is fenced and requires High – to be bank of creek from 1999/2000 riparian fringe planting completed floods. progressively from 2001 on 1435 West bank of creek unfenced and Separate the floodplain area from High under pressure from cattle. other paddock with fencing along creek channel and manage as a separate land unit. 1495 Most remnant vegetation fenced Fence wetland and associated High and in excellent condition. Large fringing buffer vegetation. wetland is unfenced and fringe is degrading from stock access. 1495 Broad flat area draining into Survey area, construct ‘w’ drains Medium wetland (above) needs shallow ‘w’ into the wetland basin drains to enhance runoff, prevent waterlogging and direct fresh water into wetland. 1497 Western bank of creek is fenced Fence wetland flats on south Medium and carefully managed as a eastern section to separate floodplain paddock. Eastern side of floodplain from other paddock. channel needs similar management 1497 Wetland chain extending from large These wetlands have been Medium- remnant vegetation block adjoining recently fenced and are being ongoing this location needs rehabilitation. gradually revegetated around the 2002 fringe to compliment the natural regeneration that is occurring. 1497 Wetland fencing and revegetation Drill a series of observation bores Medium-to may impact on groundwater levels across the wetland landscape for be completed as vegetation and regrowth regular monitoring by landholder. 2002 becomes established. 1496 Creek channel more defined, 75% Complete creek fencing. High of channel fenced, including double fencing on northern third of channel 25 Large waterlogged area becoming Fence and revegetate area to Medium - bare when dry, with scalding protect bare ground and utilise Project to be appearing. more water. undertaken during 2002 1821 Bare scalded ground at top of creek Fully enclose in fencing and Medium line revegetate. 15 9.0 Conclusion

This report has brought together information about the Lake Gore and Coobidge Creek 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.

With the bulk of the watercourse protection work completed, the 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 Agriculture WA 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 Lake Gore and Coobidge Creek wetlands long into the future.

16 Appendix 1

Location Map of

Coobidge Creek and Lake Gore wetlands

17 Appendix 2

Map of Revegetation and fencing projects 2002

18 Appendix 3

Wetland Aerial and Ground photographs, 2001

19 Appendix 4

Coobidge Creek Foreshore Survey

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