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2. Catchment Information

Catchment Information and Statistics

 

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Location	Vegetation Resources
The Valleys	Social Profile
Climate	Cultural Heritage
Geology	Population
Surface Water Resources	Household Income
Groundwater Resources	Employment
Soil Resources	Agricultural Industry Profile

 

Location

 

The Central West catchment includes the Castlereagh, Bogan and Macquarie River valleys and covers an area of approximately 92,000 km2 and is home to 240,000 people. The Central West Catchment is located in central western New South Wales, flanked by the Barwon and Darling catchments to the north and west, Lachlan to the south and the Sydney/Shoalhaven Basin to the east. Major townships include Orange, Bathurst, Dubbo, Mudgee and Nyngan. The region possesses a wide diversity of landforms, vegetation species and communities.

 

 

The Valleys

 

The Castlereagh Valley

 

The Castlereagh River rises in rugged broken country in the Warrumbungle Range at elevation of about 850 metres and flows eastwards to the town of Coonabarabran. The river then enters hilly country and flows in a southerly direction to the town of Binnaway. Downstream of Binnaway the river begins a sweeping change in direction to the northwest. In the extreme northern section of the valley the floodplain between the Barwon and Castlereagh Rivers is intersected by Womat and Wanourie Creeks, which carry flows from the Barwon to the Castlereagh River during major floods.

 

The Macquarie and Bogan Valleys

 

The Macquarie River is formed by the joining of the Campbells and Fish Rivers, which drain a high plateau area centred near Oberon with a general elevation above sea level of 900 to 1000 metres. The river flows northward through steep gorge areas in the Hill End area and is impounded by Burrendong Dam upstream of Wellington. The Cudgegong River also flows into Burrendong Dam from the northeast. Downstream of the dam the river continues to flow in a northwest direction through Wellington and Dubbo and is joined by several major tributaries from the east and western parts of the catchment. At Narromine the river takes a dramatic turn to the north and a complex system of anabranches and effluent creeks, connecting the Macquarie, Darling and Bogan Rivers commences. The Macquarie Marshes are located toward the end of the catchment, although the Macquarie River does emerge from the wetlands before being joined by the Castlereagh River and then flowing into the Barwon River near Brewarrina.

The Bogan River rises in the Harvey Ranges between Parkes and Peak Hill and flows northwest through a broad, flat landscape through Nyngan to join the Darling River near Bourke.

The landscape of the Central West catchment varies markedly from  east to west, and can be split into three general divisions: the headwaters or tablelands, the slopes and the plains. The tablelands are characterised by fast to moderately flowing streams with sandy and pebbly beds, steep, densely vegetated ranges to extensively cleared grazing lands. The slopes are characterised by undulating to hilly cleared lands, graduating to flatter areas, with some pockets of remnant vegetation. The plain areas are characterised by broad flat landscapes and the occasional rocky range outcrop. The land flattens to the west, with wetlands and rich alluvial river flats associated with braided channels and effluent streams becoming increasingly evident. The velocity of flow is low and there are extensive silt deposits.

Download Map: Central West CMA Area

 

 

Climate

 

At higher elevations in the east, temperatures vary from a winter average minimum of 0oC to a summer average maximum of 25oC. Further west at Bourke, the average winter minimum temperature is around 3oC, ranging up to an average maximum summer temperature of 37oC. The full ranges of temperatures from œ16oC to over 50oC are recorded within the catchment. Average annual rainfall varies from 900 mm along the eastern part of the catchment to 300 mm in the lower western reaches. Rainfall is clearly summer dominated in the Castlereagh Valley, while rainfall is evenly distributed throughout the year in the Macquarie. Rainfall variability increases from east to west and summer rainfall is generally more variable than winter rainfall. Source: Bureau of Meteorology (1991) Climate of NSW. Department of the Arts, Sports, the Environment, Tourism and Territories, Commonwealth of Australia.

 

 

Geology

 

Most of the land surface in the upper part of the Macquarie Valley upstream of Dubbo, and in the Bogan Valley east of Cobar, is formed on and underlain by ancient fractured rocks, both igneous and sedimentary. These rocks were deposited more than 350 million years ago, and have been folded, faulted, metamorphosed and in places Page 14 intruded by granites. The remainder of the land surface is developed mainly on horizontal sedimentary rocks of the Gunnedah and Great Artesian Basins, and overlying unconsolidated sediments. The horizontal sedimentary rocks were laid down between 290 and 150 million years ago. Areas of horizontal volcanic rocks occur at the head of the Castlereagh Valley and near Orange.

These rocks erupted from the Warrumbungle and Canobolas Volcanoes 18-11 million years ago. The young unconsolidated sediments were deposited on floodplains, piedmont plains and hillslopes. In the Macquarie Valley upstream from Narromine and the Castlereagh Valley upstream from Gilgandra, alluvium forms narrow floodplains on valley floors eroded in older rocks. Colluvial deposits frequently mantle the footslopes of these valleys. Piedmont plains are moderate to gently sloping surfaces composed of coalescing alluvial fans at the foot of ridges or mountains. They occur at the foot of the Warrumbungle Mountains and in the Talbragar headwaters. Downstream from Narromine and Gilgandra, the floodplains widen and merge into the Darling Riverine Plain, a major depositional landscape that includes the Macquarie Marshes. In the central areas adjacent to the ancient fractured rocks, there are exposures of sandstones and siltstones which form the intake areas for the Great Artesian Basin.

Farther to the west these strata are covered by a thick sequence of mudstone and shale, and the main artesian aquifers are found at great depth. Sources: Meakin, N.S. & Morgan, E.J. (compilers) 1999. Dubbo 1:250 000 Geological Sheet SI/55-4, 2nd Edition Explanatory Notes. Geological Survey of New South Wales, Sydney xvi + 505 pp. New South Wales Department of Mineral Resources 2002. Geology œ Integration and Upgrade. NSW Western Regional Assessments, Brigalow Belt South Bioregion (Stage 2). Resource and Conservation Assessment Council, NSW Western Regional Assessments Project Number WRA / 19. Watkins, J.J. & Meakin, N.S. 1996. Nyngan and Walgett 1:250 000 Geological Sheets SH/55-15 & SH/55-11, Explanatory Notes. Geological Survey of New South Wales, Sydney 112 pp.

 

 

Surface Water Resources

 

Water Quantity

 

The upper reaches of the Bogan and the Castlereagh River are largely unregulated rivers. In the Macquarie valley there are 2 main dams regulating flows. Windamere Dam on the Cudgegong River upstream of Mudgee has a capacity of 368,000 megalitres and Burrendong Dam located at the junction of the Macquarie and Cudgegong River has a capacity of 1,189,000 megalitres and is located just upstream of Wellington.

There are a number of weirs along the length of the Macquarie River including, Dubbo, Narromine, Gin Gin and Warren. The regulated section of the Macquarie extends from Burrendong Dam to Pillicawarrina in the Marshes and includes Bulgeraga Creek, Duck Creek and Gunningbar Creek. Other rivers and creeks in the catchment that have their flow augmented by river regulation include the Ewenmar system, the lower Bogan River, Marra and Crooked Creeks, the Marthaguy Creek and the lower Macquarie River. River regulation and water extraction has had substantial effects on flow.

Seasonal patterns have changed, flow variability has reduced and there are fewer large floods with long periods between inundations in the Macquarie Marshes. With regulation, flows tend to be less and more constant. In 2004, the Macquarie-Cudgegong River Management Committee developed a Water Sharing Plan for the Macquarie and Cudgegong Regulated Rivers that outlines a range of operational flow rules to remedy some of the impacts of river regulation. It is expected that given suitable flow conditions, wetlands, birds and fish breeding and river health will improve. All other streams within the catchment are regarded as —unregulated“.

Impacts on the natural flow regime of these streams are largely a result of extractive demand and the construction of town water supply schemes. The level of impact within the catchment areas varies according to extractive demand and available flow. Each of the sub-catchments has been assessed for hydrological stress as part of the Stressed River Assessment for the Central West Catchment (2000). In 2004, the Central West Unregulated Streams Management Committee (CWUSMC) developed a Water Sharing Plan for the unregulated section of the Castlereagh River above Binnaway, to provide a balance between extraction and the maintenance of instream environmental values.

 

Water Quality

 

There is unlikely to be a single stream within the Central West Catchment that does not at some time suffer from at least one of the water quality problems that would inhibit beneficial use (consumptive and non-consumptive). The degree and frequency of impact will vary enormously throughout the catchment. There are generally increasing trends for different parts of the catchment in chemical contamination (nutrients and pesticides), temperature, bacteria levels, heavy metals, turbidity, salinity, and pH. Due to the nature of the Macquarie River, most salt generated in the uplands and slopes is deposited back into the landscape through irrigation, floodplain entrapment or deposition within the wetlands and effluent systems of the western areas. However, some proportion of the salt load is discharged to the Barwon-Darling River system.

A series of maps were completed to provide an indication of the relative threats or hazards to the condition of surface water quality in the Central West catchment. These maps were compiled for the accreditation process for the Central West Blueprint by the Resource Information Unit, Department Land and Water Conservation (2003). These maps provided only as an indication of possible occurrence relative to other subcatchments in the Central West and have not been included with this document to prevent confusion with actual occurrence.

 

 

Groundwater Resources

 

Groundwater is an important resource to towns, farmers and industry in the Central West Catchment, and also makes a substantial contribution to maintaining aquatic environments. There are a number of groundwater systems in the Central West Catchment that feed many surface water ecosystems and often provide the base flows in streams and rivers. The primary threats to groundwater are from extraction and contamination.

There are groundwater aquifers within the Central West that have usage exceeding sustainable yield, there are others where the current allocation, although not active, if activated would exceed sustainable yield, and there are groundwater aquifers in both urban and rural areas that have been contaminated. An assessment of factors contributing to the decline of groundwater resources was made in the Aquifer Risk Assessment, DLWC 1997. These factors included:

• Relationship between Sustainable Yield and extractive allocations;

• Interference effects from pumping;

• Small or large flow systems (storage capability);

• Vulnerability of the aquifer to pollution;

• Land use threats;

• Proximity to poor water quality;

• Water level rise and salinity trends; and

• Dependence of ecosystems.

A series of maps were completed to provide an indication of the relative risk to the groundwater water quality in the Central West catchment. These maps were compiled for the accreditation process for the Central West Blueprint by the Resource Information Unit, Department Land and Water Conservation (2003). These maps provided only as an indication of possible occurrence relative to other subcatchments in the Central West and have not been included with this document to prevent confusion with actual occurrence.

 

Soil Resources

 

The soils of the catchment vary according to geology and landscape. Soil health issues can be broken up into three components œ fertility (salinity, acidity, nutrients), biology (the number, condition and type of soil biota) and physical characteristics (structure, sodicity and erosion). There is a high degree of interaction between the causes and effects relating to fertility, biological activity and physical characteristics.

Tablelands In the tablelands, high total rainfall has led to lower nutrients and poorer soil types. Generally, the geology of this area is dominated by coarse grained, acidic rocks resulting in sandy textured soils that are susceptible to erosion. Soils have mainly developed in-situ. Slopes The slopes are characterised by variable geology with soils developed by colluvial and alluvial activity. Generally, the soil types are less fragile and have higher nutrient levels. A lot of these soils have naturally high salt stores in Page 16 their profile, therefore increasing the risk of land degradation due to salinity.

The tablelands and slopes have ratings of poor soil health, but there is a trend toward improved cropping and grazing management practices. Plains The plains are dominated by alluvial and aeolian soil development. These soil types have higher fertility, cation exchange capacities and clay contents. The soils have a high shrink/swell potential and are susceptible to compaction problems. Acidity has not been an issue in the past due to lower total rainfall, but intensive agriculture is causing the acidity hazard to increase. A series of maps were completed to provide an indication of the relative threat to soil health in the Central West catchment.

These maps were compiled for the accreditation process for the Central West Blueprint by the Resource Information Unit, Department Land and Water Conservation (2003). These maps provided only as an indication of possible occurrence relative to other subcatchments in the Central West and have not been included with this document to prevent confusion with actual occurrence.

 

 

Vegetation Resources

 

At the time of European settlement, the Central West catchment supported a complex mosaic of forests, temperate and semi-arid woodlands, wetlands, shrub lands, heaths and grasslands. Clearing and subsequent degradation has reduced this natural vegetation cover to a large number of small, isolated remnants on the less fertile and productive soils. For example, the Box and Ironbark woodlands which originally occupied large parts of the slopes and plains have been reduced by as much as 90%, and are now among the most significantly altered plant communities in New South Wales.

In many instances, the dominant species of those communities which have been heavily cleared are still relatively common in the landscape. However, remnants often occur as single trees or small groups of mature or senescent trees; these stands typically have little, if any, of the original understorey structure and species diversity, have no regeneration, and have essentially ceased to exist as functional ecosystems. In the case of native grasslands, remnant elements are generally scattered throughout the improved pastures, which dominate much of the region, as well as roadside remnants and travelling stock routes.

Recent years have seen a growing recognition across all levels of government and the wider community of the role played by native vegetation in achieving a range of conservation, land management and water quality objectives. A number of studies have quantified the benefit of native vegetation for agriculture in aiding in the control of soil erosion and watertable levels; the role of native vegetation as reservoirs of native fauna and flora is relatively self-evident. The small size of many remnants means that internal process, and therefore their sustainability, is dominated by external pressures.

Recognition of the impact of these processes on native vegetation has increased awareness of the need to shift towards an approach which emphasises management and research of landscape function and the role of the various abiotic and biotic elements in ecosystem processes at the landscape scale. In the future, successful management of native vegetation will depend on development of a coordinated and strategic approach to management of the whole landscape. Central to such an approach will be strategies that relate to the retention, restoration, enhancement and revegetation of key areas.

 

 

Social Profile

 

The Central West catchment has diverse range of people and industries. The Catchment supports the major centres of Bathurst, Orange, Mudgee and Dubbo. There are also many other small but significant townships including; Coonabarabran, Binnaway, Mendooran, Carinda, Quambone, Coonamble, Gulargambone, Coolah, Oberon, Molong, Rylstone, Gulgong, Dunedoo, Wellington, Gilgandra, Tooraweenah, Warren, Trangie, Tottenham and Nyngan.

The catchment also supports a diverse range of industry including; agriculture, agribusiness, tourism, mining and viticulture. The figures used in this social profile have been taken from the 2001 ABS Census data. This is the most recent official data for description of population trends. The next Census will be undertaken in 2006 and the corresponding results will be incorporated into the Catchment Action Plan. The total population of the Central West Catchment based on 2001 Census was 185,515 persons incorporating a total indigenous population of 11,688 persons, which is 6.2% of the total population of the catchment.

 

 

Cultural Heritage

 

The major Aboriginal nations that the Central West Catchment area overlies are the Wiradjuri, Kawambarai, Weilwan, Wongaibon . These nations extend into other Catchment Management Authorities also. Small parts of the Aboriginal nations of the Dharuk, Darkinung and the Gamilaroi also extend into Central West CMA. The Board recognises that land is of great significance to Aboriginal people for spiritual values but also plays a role in social relations, political relations and the cultural construction and transmission of knowledge. In NSW, the inland rivers and surrounding areas supported the largest Aboriginal communities, had the most innovative societies and were the most active traders of material goods and intellectual property.

 

 

Population

 

Table 1 below shows population statistics for the Central West catchment according to age distribution.

Items	Male	Female	Total	Indigenous Males	Indigenous Females	Indigenous Persons
Aged 0-14 Years	23458	22067	45525	2570	2463	5033
Aged 15-64 Years	58361	57782	116143	3126	3238	6364
65 Years plus	10253	13074	23327	122	169	291
Overseas visitors	195	325	520	0	0	0
Totals	92267	93248	185515	5818	5870	11688

Source: Australian Bureau of Statistics, CDATA 2001

 

The total population of the Central West Catchment in 1991 was 176,857 persons. This increased to 182,885 persons during 1996 and then to 185,956 persons during 2001. Orange has largest urban population in the Central West Catchment. During 1991 to 1996 census the population in Orange grew at an annual average of 0.6% during 1991-96 census and it increased to 0.9% during 1996 - 2001 census. Population growth also took place in Bathurst, Cabonne, Dubbo, Evans and Mudgee. Bathurst, Dubbo, Mudgee and Orange are the largest population centres in the catchment, accounting for 63% of the entire catchment population in 2001. It is also worth noting that Evans Shire is now part of Bathurst Regional Council and Coolah is part of the new Warrumbungle Council.

 

Household Income

 

Table 2 presents distribution of households according to gross weekly income. The average gross weekly household income is divided into three categories: Low (less than $299), Middle ($300 œ $999) and High ($1000 and above). A greater percentage of the Central West Catchment household income falls in the middle and high- income brackets, which is consistent in comparison with NSW.

 

Employment

 

Employment data for the Central West Catchment is presented in Table 5. Total employment in the Catchment was 78,438 persons in the 2001 Census. The unemployment rate for the catchment is 7.7% which is 0.5% higher than the State estimates. The male unemployment rate in the catchment was 0.3% higher than the NSW estimates and female unemployment rate was 0.7% higher than the entire state estimates. Figure 3 shows employment based on location in the catchment.

 

Employment by Industry

 

Data from censuses taken between 1991 and 2001 indicate the main industries in the central west catchment consist of agriculture, manufacturing, retail trade, education, property and business services and health and community services. In 2001, the share of agriculture in total employment was 13%, manufacturing was 10%, retail trade was 15%, health and community services was 10%, education was 8% and property and business services was 7% respectively. Other important industries include construction, accommodation, cafes and restaurants, property and business services. Since 1996 employment has increased in all industries with exception to communication and government, finance and insurance and administrative services.

 

Agricultural Industry Profile

 

Census data from 2004 indicates that were 5,407 agricultural establishments in total consisting of 298 horticulture and fruit industry establishments, 4,712 grain establishments, 42 sheep and beef cattle framing establishments, 4 dairy cattle farming establishments, 231 poultry farming establishments and 120 other livestock farming establishments. Grain establishments were 87% of the total establishments in the catchment.

Mudgee had the highest number of establishments with a total of 589, followed by Parkes with 541 agricultural establishments and Wellington with 428 agricultural establishments. Parkes had highest number of grain establishments with a total of 514 followed by Mudgee with a total of 490 and there were 395 establishments in Wellington.

 

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Further Information:

If you would like more information from the Central West CMA please email: cw@cma.nsw.gov.au