Merri Creek Management Committee

Chapter 3.3 Aquatic Flora, Fauna and Wetlands

Regional Port Phillip & Westernport Catchment Strategy Objective: RCS-WO2: Protect and improve the environmental health and social and economic values of waterways and wetlands. RCS-BO2: Maintain the diversity of indigenous habitats and species in terrestrial, aquatic and marine environments. Relevant Regional Targets: RCS-WT3: Diversions from all waterways to be within sustainable diversion limits by 2015. RCS-WT6: Improve the condition of the regions waterways so that: - at least 50% of all natural waterways will be in good or excellent condition by 2015; - all natural waterways will be in good or better condition by 2025. RCS-WT7: Progressive improvement in the condition of waterways across the region as measured by the Index of Stream Condition, including beds and banks, streamside zone and aquatic life. RCS-WT15: No net loss in the extent and health of wetlands of each existing type. RCS-WT16: Progressively improve the overall health and social value of natural wetlands, including those that are nationally and internationally recognised. RCS-BT7: Increase the diversity of native species in modified landscapes and aquatic systems. RCS-BT9: No human-induced reduction in species diversity for the freshwater, estuarine and marine environments of the region.

Background

Merri Creek, its tributaries and associated wetlands support a range of aquatic and semi-aquatic animals, plants and communities. Faunal groups include:

• Micro-organisms
• Aquatic macro-invertebrates
• Fish
• Aquatic mammals (Water Rat, occasional visiting Platypus)
• Water-dependent bats (e.g. Myotis species)
• Amphibians (various frog species)
• Reptiles
• Waterbirds
• Various terrestrial species which use the waterways for drinking-water

Floral groups include:

• microscopic and macroscopic algae
• submerged, emergent and floating species of flowering plants
• species of the banks, floodplain and other riparian areas which depend on the waterway environment, including those needing flooding for dispersal.

A healthy waterway requires a suite of physical and chemical conditions in order to sustain populations of animals and plants. For streams, many of these conditions are specified in the SEPP objectives discussed in chapter 3.2.

Physical Parameters

The physical parameters include:

• a stable substrate;
• stable banks;
• variable habitat niches (pools, riffles, woody debris);
• absence of artificial barriers to movement (particularly important for migratory fish);
• variable micro-climate provided by vegetation with a mix of light and shading probably more lightly shaded than waterways to the east of Melbourne;
• provision of a steady supply of energy/food;
• low levels of turbidity/suspended solids such that (a) light is able to penetrate the waters to permit photosynthesis and sustain food sources for in-stream fauna, (b) organisms and substrate are not smothered by excessive amounts of fine sediments.
• temperatures not excessively above or below seasonal norms so that breeding patterns of in-stream fauna are not disturbed and any flow-on effects (e.g. impacts of low dissolved oxygen) are not produced; and
• stream flow and hydrologic conditions which sustain aquatic communities.

In addition, for species which spend part of their life-cycle away from the aquatic environment, e.g. Growling Grass Frogs, the terrestrial environment must also provide suitable conditions to sustain populations and a variety of waterway/wetland types need to be accessible.

Chemical Parameters

The chemical parameters include:

• sufficiently high levels of dissolved oxygen to support the respiration of a diversity of aquatic organisms;
• salinity levels of a sufficiently low magnitude that the diversity of flora and fauna in the stream and its riparian zone is not depleted (n.b. some Merri waterways probably have a natural tendency towards somewhat saline conditions and may suffer if salinity is reduced e.g. saline adapted plant communities upstream of Craigieburn STP) ;
• nutrients (phosphorus and nitrogen) below levels which encourage excessive growth of filamentous and toxic algae growth which alters macro-invertebrate community structure and stream health;
• moderate pH levels such that in-stream flora can grow and the toxicity of other pollutants is not altered or released into the water column;
• Biological Oxygen Demand (BOD - the amount of oxygen required by the biological processes taking place in the water) low enough to not unduly affect levels of dissolved oxygen; and
• levels of heavy metals (e.g. copper, cadmium, chromium, arsenic, lead, zinc, mercury) and other toxicants in water and in sediments below levels harmful to aquatic life.

Where most of these fundamentals are in place, waterways can sustain a diverse and healthy range of aquatic life.

Aquatic macroinvertebrates

Macroinvertebrates are animals without a backbone, visible to the naked eye, and include shrimps, snails, water fleas, worms and insects. They are commonly referred to as water bugs.

As discussed in 3.2 the condition of the macroinvertebrate community provides a sound indication of the level of ecological health of a stream. Macroinvertebrates are a key element of the food chain as they eat organic debris (leaves etc), and plants within the stream, as well as being eaten by larger invertebrates, which in turn are food for birds, Platypus and fish.

Those macroinvertebrates found in Merri Creek tend to be the hardier, wide-spread forms found across lowland streams in south-eastern Australia. This is particularly the case for the urban stream sections. Most surveys have not identified macroinvertebrates to the specific species level, as this is not necessary for assessing general stream health. The vast majority are indigenous species, although a few introduced species, widely found in Victorian streams are found in the Merri including the aquatic snail, Physa.

The Ecowise (2005) report commented that sites upstream of the Craigieburn Sewage Treatment Plant may contain unique aquatic habitats and macroinvertebrate species &that have significant conservation values& (p.47). In other words, there is a level of detail in the makeup of the aquatic macroinvertebrate communities that is yet to be investigated and assessed.

Fish

Overall there is a paucity of fish numbers and species diversity in Merri Creek[240] (Amenta 2002), perhaps a function of poor water quality and lack of habitat. Koster (2002) recorded Short-finned Eels as the most abundant fish species, in Merri Creek. Common and Broad-finned Galaxias were found only below the Craigieburn Sewage Treatment Plant (STP), and River Blackfish and Flat-headed Gudgeon only found above it, though this apparent relationship may be spurious. Earlier reports have also recorded Spotted Galaxias, Tupong and Australian Smelt. All of the above are native fish species.

The introduced Eastern Gambusia (or Mosquito Fish) was the second most abundant species found by Koster (op cit). Other exotic fish which have been recorded include Goldfish, Carp, Oriental Weatherloach, Rainbow and Brown Trout, and Roach.

There is no specific information available on fish in the tributaries of the Merri.

In the past, barriers in the form of Dights Falls (on the Yarra), and the walls at Coburg Lake (on the Merri) and Edwardes Lake (on Edgars Creek) have prevented fish migration upstream in the Merri. A further 18 less significant barriers in the Merri Creek and tributaries have been reported (Doeg and Curmi, 1994 in Finlay, McGann and Roy, 1996). These barriers, plus the presence of pest exotic species such as Carp and Mosquito Fish, have reduced the numbers of native fish in the stream, although Blackfish is still present in the upper catchment (Schulz and Webster, 1991), and is considered regionally significant due to its rarity in this and surrounding catchments.

A fish ladder was installed in the late 1990s at Dights Falls, on the Yarra just below the confluence with the Merri. Finger (1998) assessed that the ladder was only partially working as water velocities had not been sufficiently reduced. Melbourne Water is currently investigating the potential to improve the fish ladder as part of a project to rebuild the weir.

In March 2001 a fish ladder was installed at Coburg Lake, and Koster (2002) evaluated the success of this rock ramp fishway by undertaking a pre and post fish survey. He found that the distribution and /or abundance of the three migratory native species, Common Galaxias, Broad-finned Galaxias and Short-finned Eel, was greater post fishway construction. Nevertheless, abundances of migratory species were generally greater downstream of Coburg Lake compared with abundances upstream. Koster suggested upstream passage may have been restricted for a number of reasons including vertical drops within the fishway and high velocity of water. Although Amenta (op.cit.) reports that additional works have been undertaken to remedy the vertical drops, the Merri Creek Waterway Activity Plan (Melbourne Water 2003) notes that some minor improvements to the Coburg Lake Fish Ladder are likely to be needed to improve fish passage to a wider range of species.

The installation of a fish ladder at the Edwardes Lake weir was investigated in 2000 as part of the Edwardes Lake Redevelopment study undertaken for Darebin Council by Woodward Clyde. The draft sketch involved a covered channel in places 4.5 m below ground level and costing around $60,000. The suggestion was shelved without further investigation.

The Draft Merri Creek Waterways Activity Plan (Melbourne Water 2003) mentions investigating whether a historic ford at Craigieburn Grasslands (Galgi ngarrk) is a fish barrier, however fails to mention the two more significant fords downstream at OHerns Road and just north of Cooper Street.

Amphibians

Melbourne Waters Frog Census reports seven frog species are found in the Merri Catchment. These include the Southern Brown and Whistling Tree Frogs, Growling Grass Frog, Common Froglet, Victorian Smooth Froglet, Pobblebonk Frog and the Spotted Marsh Frog.

In the past five years significant remnant populations of the nationally listed[241] Growling Grass Frog have been identified within the Merri catchment. Some of these are associated with off-stream water-bodies, particularly quarry holes, but breeding habitat for two key populations includes pools within the stream itself (on the section of Merri Creek between OHerns Road and Cooper Street) and in the Merri and Kalkallo Creeks in the vicinity of Donnybrook/Kalkallo (Heard et al 2004).

Growling Grass Frogs were once far more widely distributed along the Merri and Edgars Creeks than now with (recent) historic records as far south as Fawkner. Heard (2007) has identified 16 sites in the Merri catchment and another 13 nearby at which Growling Grass Frogs appear to have permanently disappeared. Nine sites in the catchment have lost their populations of the frog in the last 8 years. Maintaining connections between on-stream and off-stream habitat and re-establishing habitat linkages at a landscape level is essential for the future conservation of this species. Further information about the Growling Grass Frog can be found in section 2 of this report.

Frog populations are affected by the chytrid fungus, which has been decimating frog populations worldwide, by loss of breeding and feeding habitat, loss of movement corridors (often over land), by exposure to toxins including some herbicides and predation by exotic species, especially Mosquito fish.

The Queensland and NSW Eastern Dwarf Tree Frog (Littoria fallax) has unfortunately been introduced into certain wetland habitats along the lower Merri Creek. Its impact is unknown, but there is potential for it to compete with local indigenous frogs such as the Southern Brown Tree Frog (Littoria ewingi)

Many frogs can benefit by the creation of intermittent wetlands fed by clean drainage water. They are also known to colonise stormwater treatment wetlands, though this has to be considered a somewhat uncertain habitat because of the build up of toxins in the sediments. It is particularly felt that stormwater treatment wetlands should not be seen as adequate substitute habitat for Growling Grass Frogs in the face of destruction of existing habitat (Heard pers.com).

Reptiles

The only aquatic reptile known from the Merri Creek is the Common Long-necked Tortoise, although a number of terrestrial species use the Creek valley (Beardsell 1997) and may at times swim and feed in the waterways.

Birds

Of the birds known to utilise the Merri Creek corridor at least four of those considered to be of regional significance (Beardsell op.cit.) are likely to heavily depend on the in-stream habitats associated with the waterways including the Great and Little Egrets, the Nankeen Night Heron and the Sacred Kingfisher.

These and other bird species would benefit from water quality and habitat improvement in-stream, and from an increase in wetland habitat in the catchment.

Aquatic Mammals

The native Water Rat, or Rakali, is still common in Merri Creek, with 50% or more of sites investigated having Rakali present (Williams & Serena 2004).

Although Beardsell (1997) reported a sighting of Platypus upstream of Summerhill Road in 1991 (see section 2.1), Platypus appear no longer to be resident in Merri Creek. Amenta (2002) reported a number of sightings in the lower Merri which she attributed to Platypus visiting the Merri from the Yarra River to forage for food.

Serena and Pettigrove (2005) have identified the availability of macroinvertebrates as a possible major factor limiting the distribution of Platypus in urban streams of Melbourne. Pettigrove has suggested that the toxicity of sediments in the Merri Creek and the subsequent paucity of macroinvertebrate numbers is likely to be the key factor precluding Platypus from the Merri (Pettigrove pers.com).

Aquatic and riparian plants and communities

Terrestrial flora and fauna of Merri Creek and its tributaries are discussed in Section 2 Flora, Fauna and Linear Parkland.

Aquatic and riparian ecological vegetation communities[242] recognised for Merri Creek and its tributaries include: Creekline Grassy Woodland (EVC68), Grey Clay Drainage-line Herbland-Sedgeland Aggregate (EVC 124), Plains Grassy Wetland (EVC 125), Aquatic Herbfield (EVC 653), Creekline Tussock Grassland (EVC654) and Streambank Shrubland (EVC 851).

One of these EVCs (Plains Grassy Wetland) is considered extinct in the Victorian Volcanic Plains Bioregion[243], and all the others are considered endangered. (See Table 6 in chapter 2.1)

A report by GHD (2004) identified a range of species adapted to the natural salinity in the riparian fringe of Merri Creek above the Craigieburn Sewage Treatment Plant (STP). Some of these species are regionally significant. This community does not exist downstream of the STP, presumably because of the constant and fresh flow provided by the treated effluent from the STP.

Downstream of the STP, sections of the Merri Creek riparian zone are dominated by tall, dense stands of Common Reed (Phragmites) the growth of which appears to be stimulated by the supply of nutrients in the discharged effluent. Frood has described this downstream community as simplified compared to the saline-adapted community found upstream (Frood pers. com). The Merri Creek WAP also identifies excessive growth of Phragmites as a problem.

Apart from its intrinsic value, riparian vegetation benefits the aquatic environment by controlling sediment inputs, and providing food, shelter and shade. Where it has been damaged, the vegetative cover of the streams banks can be improved to provide better habitat for in-stream fauna. .

Photo 2 - MCMC revegetation work at Queens Parade in 2007 Near bank was revegetated in 2001, far bank in 2005

Recent work undertaken by Melbourne Water and MCMC has paid particular attention to the riparian verge habitat. Examples include MCMCs work downstream of Queens Parade Fawkner, and Melbourne Waters work between Normanby Avenue Thornbury and St Georges Road Northcote

Primarily constructed as a sediment detention basin, the Leamington Street Wetlands on Edgars Creek in Reservoir, are a good example of aquatic and riparian revegetation and its role in sediment control as well as for habitat.

Where indigenous vegetation remains on the banks of the waterways it should be retained. Areas of reasonably intact riparian scrub and grassy woodland/floodplain areas along the middle to upper reaches of Merri Creek provide a strong basis for improving the riparian and stream corridor.

Riparian weeds

Many species of riparian weeds are established in the Merri Creek catchment[244]. They have a major impact on the waterway ecosystems. The impact and management of weeds is also dealt with in section 2 and chapter 3.1 of this report.

Non-indigenous trees such as willows, poplars and elms have limited habitat value when compared to native vegetation, and inhibit native vegetation and are classified as environmental weeds. Weed trees may provide some benefits to the stream through shading and cooling the water below, and providing some in-stream shelter to aquatic life. However leaf litter pollution and flow restriction issues outweigh their ecological benefits.

Potential environmental damage done by removal of willows can be minimised by:

• planting indigenous species where possible in the gaps between the willows and allowing their establishment prior to commencement of willow removal (this may not be practical where willow infestation is dense)
• poisoning by drill and fill of live trees long enough in advance of removal to minimize re-sprouting
• removal of standing timber by cutting it from the stump and leaving the dead stump in place, following up for any re-sprouting stumps later.
• treatment in this way of sections of a willow infestation and replacement with indigenous species, especially fringing macrophytes, followed some years later by removal of the remaining willows and their replacement with indigenous species. Using this method sections should be no longer than 50m, although many sections may be treated at the same time provided they are separated by untreated sections of around the same length. Works by Melbourne Water have often sought to remove much longer sections of Willows, and it is recognised that there are budgetary savings to be accrued from larger scale works.

Aquatic weeds

A number of serious aquatic weeds are established in Merri Creek. Alligator Weed, a weed of National Significance and State Prohibited Weed because of its potential for choking waterways, was recorded in 1997. Its control is the responsibility of DPI and Melbourne Water, DPI, Melbourne Water and the City of Darebin have been keeping a close watch monitoring and treating the outbreak. However, after being dispersed by flooding by May 2007 Alligator Weed had become a frequent occurrence in Edgars Creek downstream of Leamington Wetlands and Merri Creek downstream of Edgars Creek, although further control work has been carried out in 2008 by Melbourne Water.

Egeria densa (Dense Water Weed) is well established in Merri Creek Northcote and downstream. Whilst not a listed weed, it is likely to be having a detrimental effect by excluding indigenous water plants such as Potomagetons. It is likely to be spreading upstream, but research is needed to evaluate the threat and needed actions.

Waterway Ecosystem Degradation

The waterways of the Merri catchment show indisputable evidence of a significant decline in the diversity of the waterway ecosystem due to:

• degradation and loss of physical habitat, both in-stream and linkages to floodplain (including wetlands);
• degradation and loss of riparian vegetation (especially loss of overhanging Red Gums and weed invasion);
• degradation and loss of instream vegetation;
• hydrological changes typical of urban streams resulting from higher flashiness[245] of flows; stream flow change associated with the constant level of discharge from the Craigieburn STP; impact of farm dams and on-stream dams on some tributaries;
• deterioration in water quality due to stormwater inputs, with toxicants associated with industrial stormwater being the biggest problem;
• deterioration in water quality due to sewage overflows during high rainfall events and illegal connections or leaks from sewerage system.

Opportunities to improve aquatic ecosystems

Improvement to aquatic ecosystems in the catchment requires:

• Reductions of inputs of toxicants, nutrients and sediments from the rural and urban catchments (WSUD, sediment controls as well as appropriate rural land management can help, including protecting smaller drainage lines see Chapter 3.2)
• Improved fringing and riparian vegetation (Melbourne Waters Stream Frontage Management Program, continued support for Landcare groups, as well as MCMCs, Councils and other urban revegetation programs)
• Reduced competition for resources from weeds and introduced animal species (Melbourne Water, DPI, MCMC and Councils weed control programs)
• Improving flow regimes (reducing peakiness of flows especially helps, although some variation in flow is needed)
• Improving structural complexity and stability in the channel (encouraging pool and run form and retention of woody debris)
• Improved connection up and downstream and to the floodplain (continued removal of fish barriers, wetland protection, restoration and creation)

Wetlands

A wetland is a site ...where&wetness of the land is sufficiently frequent and sustained to influence the composition of the associated vegetation. (DSE 2006). Wetlands vary widely and some may not hold water for years at a time. Two wetland vegetation types in Merri Creek are Plains Grassy Wetland and Wet Verge Sedgeland.

Wetlands are productive ecosystems providing habitat for native animals and plants, including rare and threatened species. They assimilate and recycle nutrients and trap sediments. They act as flood control basins, assisting in the hydrological stability of the catchment. Wetlands are sites of cultural, scientific, recreational, landscape and educational interest.

Apart from the waterways themselves, wetlands of the Merri catchment include:

• Shallow freshwater marshes (non-permanent)
• Artificial lakes
• Artificial wetlands
• Quarry holes
• Farm dams

None of these are nationally or internationally recognised wetlands although some are listed on a state level as biosites of national significance (e.g. Hernes Swamp).

Major shallow freshwater marshes include the remnants of Hernes Swamp, Inverlochy Swamp, and Camoola Swamp. The wetlands originally thought to be present in the Merri Creek Catchment are shown on Map 16. The total area of wetlands shown on the map is approximately 2,140 ha. This compares with a total of approximately 83 ha recorded as retaining wetland vegetation in the catchment. Another comparison is with water areas recorded on VicMap mapping, which records a total of 318ha of watercourses, lakes, dams, pondages and areas subject to inundation[246]. No areas are recorded as being swamps in the VicMap mapping.

Clearly wetlands in the Merri Catchment have been decimated by settlement, although the exact extent of remaining swamps is very unclear as there has been no catchment wide wetland study.

There is potential to re-establish a number of swamps, an initiative that would provide enormous habitat benefits as well as flood control and water quality treatment. Wetland ecological communities are identified as a high priority for restoration in the Port Philip and Western Port Regional Native Vegetation Plan. Achieving significant wetland restoration in the Merri Catchment needs a champion, as well as a strategy.

A small ephemeral wetland remains at OHerns Road. This land has been identified as a high priority for inclusion in the new Merri Park (Marran baba).

Three significant lakes have been established in the urban part of the catchment. They are permanent open freshwater wetlands, and include Coburg Lake (on Merri Creek), Edwardes Lake (on Edgars Creek), and Jack Roper Reserve Lake (on Merlynston Creek). Coburg Lake and Edwardes Lake were established for ornamental and recreational purposes, although water contact is now not desirable because of water quality issues. Jack Roper Reserve Lake forms part of a retarding basin.

Habitat values of these lakes has been limited given the limited fringing vegetation, hard edges and poor water quality. Recent remodelling of Edwardes Lake has resulted in greatly improved riparian vegetation and a significant wetland area.

Photo 3 - Campbellfield Creek Retarding Basin wetland development

As discussed in 3.2 a few artificial wetlands have been established with habitat provision as their primary purpose; the wetland at Strettle Reserve in Thornbury is an example. However many small wetlands have been established for stormwater treatment with habitat provision as an important additional benefit. These include wetlands at Hall Reserve and Walker St in Clifton Hill, Merri Park Northcote, Campbellfield Creek Retarding Basin, Malcolm Creek Craigieburn, Roxborough Park, and Somerton. Some of these wetlands are providing important habitat functions, for example the wetland adjacent to Frog Court in Craigieburn and the Leamington Street Wetlands on Edgars Creek have been colonised by Growling Grass Frogs.

Stormwater treatment wetlands may not provide ongoing habitat however. Periodically they need to be de-silted, and this can severely (but temporarily) impact on habitat values.

The fact that many of the wetlands of Merri Creek are ephemeral does not diminish their value as habitat. Seasonal wetlands were a key characteristic of the pre-European landscape of the Merri catchment.

A number of quarry holes and farm dams provide important habitat for Growling Grass Frogs and other water-dependent species. Apart from frog surveys there has been no systematic survey of these habitats.

Wetlands off the major channel provide a very important role as habitat, as they can have higher water quality, and may be free of damaging exotic species like Carp and Mosquito fish.

Map 16 - Map of wetlands in the Merri catchment

 

Key references

Amenta , V. (2002) Summary of Water Quality and Stream Health Monitoring Data, Appendix 2 part B of Final Draft Merri Creek Waterway Management Activity Plan, Melbourne Water 2003

Bainbridge, B. (1999). Merri Creek Aquatic and Semi-Aquatic Planting Guide, Merri Creek Management Committee, Melbourne.

Bainbridge, B. (2005) Notes on visit to Wallan Creek 12 May 2005

Bainbridge, B.J. & Bush J.M. (1999) Lake Reserve Coburg Aquatic Vegetation Management Plan Report prepared for Moreland Council by Merri Creek Management Committee..

Beardsell C. (1997) Sites of Faunal and Habitat Significance in the North East Melbourne, A report prepared for the North-East Region of Councils (NEROC) by Dunmoochin Biological Surveys, Melbourne.

Carr, G.W., C.J. Campbell and C. Wilson (2006) Final Flora and Fauna Assessment: 700 Hume Highway, Craigieburn, Project 05-80 prepared for Macquarie Goodman by Ecology Australia Pty Ltd.

Department of Sustainability and Environment (2006) Index of Wetland Condition Assessment of wetland vegetation Update March 2006.

Finger, L. Coburg Lake Fish Ladder Feasibility, report for Merri Creek Management Committee, October 1998.

Finlay, I., McGann, J. and Roy, A. (1996) Strategy for the Restoration of the Waterways of the Merri Catchment State of the Environment Report, Merri Creek Management Committee, Melbourne.

GHD (2004) Yarra Valley Water Aurora treatment Facility Ecological Risk Assessment. Final Report, June 2004.

Heard, G., Robertson, P. and Scroggie, M. (2004) The Ecology and Conservation Status of the Growling Grass Frog (Litoria raniformis) within the Merri Creek Corridor. Second Report: Additional Field Surveys and Site Monitoring. Report for Dept Sustainability & Environment.

Heard, G (2007) Pattern and Process: Understanding the Habitat Requirements of the Endangered Growling Grass Frog (Litoria raniformis) in Urbanising Landscapes, Third year progress report to the Growling Grass Frog Trust Fund, November 2007.

Koster, W. (2002) An Assessment of the Coburg Lake Fishway Report for Melbourne Water. Arthur Rylah Institute for Environmental Research.

Melbourne Water (2003), Merri Creek Waterway Management Activity Plan Final Draft, Melbourne Water, Melbourne.

Melbourne Water (2005), Merri Creek Local Management Rules 2005.

Melbourne Water and Port Phillip & Western Port Catchment Management Authority (2007) Port Phillip and Westernport Regional River Health Strategy.

Mitchell, P.A. and Clark, H. (1991). An Environmental Study of Merri Creek, for State Water Laboratory of Victoria, Rural Water Commission of Victoria, Melbourne.

Pettigrove V. and Hoffman, A. (2003) Impact of urbanisation on heavy metal contamination in urban stream sediments: influence of catchment geology. Australasian Journal of Ecotoxicology 9, 119-128.

Pettigrove, V. and Hoffman, A. (2003c) Major sources of heavy metal pollution during base flows from sewered urban catchments in the City of Melbourne. Proceedings, 3^rd South Pacific Conference on Stormwater and Aquatic Resource Protection combined with 10^th Annual Conference of the Australasian Chapter of the International Erosion Control Association, Auckland, New Zealand, New Zealand Water and Wastes Association, May 14-16, 2003 CDROM.

Pettigrove, V. and Hoffman, A. (2005) A field-based microcosm method to assess the effects of polluted urban stream sediments on aquatic macroinvertebrates. Environmental Toxicology and Chemistry 24(1), 170-180.

Platt, D. & Halley M. (2004) Merriang Local Area Biodiversity Plan, Draft for discussion August 2004, Department of Natural Resources and Environment, Box Hill.

Port Phillip and Westernport Regional River Health Strategy, Melbourne Water 2007.

Port Phillip and Westernport Catchment Management Authority Catchment Condition Report 2004-5. PPWCMA, Melbourne 2005.

Public Interest Research Group (PIRG) (1975) The Merri Creek Study, PIRG, Melbourne.

Schulz, M. and Webster, A. (1991). Sites of Biological Significance in the Merri Corridor A Preliminary Investigation, Department of Conservation and Environment, Melbourne.

Serena M and Pettigrove, V. (2005) Relationship of sediment toxicants and water quality to the distribution of Platypus populations in urban streams. J N Am Benthol Soc

Williams, G.A. & Serena, M (2004) Distribution and Status of Australian Water Rats (Hydromys chrysogaster) in the Melbourne Metropolitan Region, Australian Platypus Conservancy report to Melbourne Water, April 2004.

Issues

1. Fish barriers, introduced fish species, and poor water quality are limiting fish diversity in Merri waterways.

2. Growling Grass Frog populations need careful management and habitat protection and enhancement.

3. Birds would benefit from improvements to water quality and wetland habitat.

4. Toxicity of sediments in the Merri Creek and the subsequent paucity of macroinvertebrate numbers is likely to be the key factor preventing Platypus from recolonising. the Merri.

5. Unusual and regionally significant instream communities occur in Merri Creek upstream of Craigieburn.

6. Willows and other riparian woody weeds are on balance detrimental to the ecology of waterways, but a sensitive process is needed for their replacement.

7. Alligator Weed has not been eliminated from Merri Catchment despite its status as a Weed of National Significance and state prohibited weed.

8. More research is needed to understand the impact and control of aquatic weeds in the catchment.

9. Improving the aquatic ecosystems of Merri Catchments waterways requires:

· Improved fringing vegetation.

· Reductions of inputs of toxicants, nutrients and sediments from the rural and urban catchments.

· Control of aquatic weeds and problematic introduced animals.

· Improved flow regimes.

· Greater structural diversity in the stream channels.

· Improved connection up and downstream and to the floodplain.

10. Wetlands have been decimated in the catchment, but are a high priority for restoration; a study is needed to strategically plan restoration and management of wetlands across the catchment.

11. Habitat values of artificial lakes in the catchment could be improved by improving their fringing and riparian vegetation.

Objectives

1. Protect and improve the environmental health and social and economic values of waterways and wetlands (see RCS-WO2).

Targets

1. Halt further decline in the condition of rural waterway sections, and by 2010 improve the condition of urban sections of the catchment from very poor to poor. In particular, in the urban sections improve vegetation from very poor to poor (see also section 2), water quality from very poor to poor and habitat and stability from moderate to good. (these targets are derived from the Regional River Health Strategy).

2. Improve the condition of the catchments waterways so that:
- at least 50% of Merri Catchments natural[247] waterways length will be in good or excellent condition by 2015;
- all natural waterways will be in good or better condition by 2025 (see RCS-WT6).

3. Progressive improvement in the condition of waterways across the catchment as measured by the Index of Stream Condition, including beds and banks, streamside zone and aquatic life (see RCS-WT7).

4. Study of the extent and health of the catchments wetlands and their restoration and management undertaken by 2010.

5. No net loss in the extent and health of wetlands of each existing type (see RCS-WT15).

6. Progressively improve the overall health and social value of natural wetlands (see RCS-WT16).

7. Return of Platypus by 2016 to the upper reaches.

8. No net loss of Growling Grass Frog populations and key habitats.

9. Diversions from Merri waterways to be within sustainable diversion limits by 2015 (See RCS-WT3).

10. Removal of fish barriers at Cooper Street, OHerns Road, and Edwardes Lake by 2015.

11. Aquatic weed control strategy undertaken by 2010.

12. Eliminate Alligator Weed from Merri Creek by 2010.

13. Increase the number of wetlands.

 

Actions

See Section E page 201.

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[240] No fish studies have been carried out on Merri Creek's tributaries

[241] Listed as vulnerable under the Federal Environment Protection and Biodiversity Act

[242] These EVCs do not include algal communities or fully instream communities

[243] It is not extinct however known examples are very degraded. For example small highly weed invaded and degraded examples were detected near Craigieburn in 2006 (Carr et al 2006)

[244] E.g. Bainbridge 2005 identified 49 weed species in a short stretch of Wallan Creek of which 19 were high priority.

[245] flashiness refers to the higher and more frequent peak flows and lower base flows associated with the decrease in permeability of urbanised catchments (see Walsh et al). Greater disconnection of the drainage system from streams using WSUD principles can reduce this flashiness. (Also occurs in rural areas as a result in clearance of deep rooted vegetation and drainage)

[246] Based on GIS analysis by MCMC 5/5/07

[247] In this context natural waterway is taken to mean one that is not in a pipe or concrete lined.