Department of Land and Water Conservation
Corner of Lynch and Lovell Streets, PO Box 223, Young NSW 2594
Phone (02) 6382 5833, Fax (02) 63822134
Young’s Environmental Initiatives Committee, made up of Young Shire Councillors and staff, Department of Land and Water Conservation and local Landcare groups, won Natural Heritage Trust funds to produce the Upper Burrangong Catchment Plan.
The Upper Burrangong Catchment Plan is based in Young (NSW) and covers an area of 20,178 hectares. It aims to collate existing information at a local scale and carry out more detailed natural resource assessments to produce a comprehensive document which would become available to the wider community.
Land and water degradation issues were identified by the local community. Aerial photo interpretation data was transferred to ArcView® Geographic Information System. All relevant data about each of the environmental degradation issues and the area of the catchment affected by each issue was extracted from the GIS to develop the Catchment Plan. The costs of continuing degradation under a “no plan” scenario for each issue were investigated.
Burrangong Creek and its tributaries export 17.4 tonnes of salt, 26.7 kg of nitrogen and 7.5 kg of phosphorus each day to downstream catchments. Land and water degradation issues in the Upper Burrangong catchment include water quality loss, rising watertables, dryland and urban salinity, soil erosion, soil acidity, declining riverine corridor health, native vegetation decline, weed infestation and soil structure decline. These issues cost the community approximately $4,559,235 as a one-off payment to maintain houses and buildings affected by urban salinity, $5,535,302 per year in lost production as well as uncosted financial losses.
The purpose of the Catchment Plan is to provide the Environmental Initiatives Committee (Young Shire Council) with a detailed study that identifies environmental degradation issues and their extent in the Upper Burrangong catchment. The project aims to increase community awareness of degradation issues in the catchment and promote ownership by encouraging community participation in producing the Catchment Plan. Through publicity, community consultation, field days and the media, the community became aware of the project and how the degradation issues identified affect them.
This two-year project was carried out in three stages:
(i) Identification of environmental degradation issues in the study area, collation of existing data on the status of natural resources in the study area and undertaking field work to complete data sets and installation of all existing data onto a Geographic Information System (GIS).
(ii) Compilation of a Catchment Plan that reports on all relevant data from the GIS, including areas affected by the various degradation issues, and considers the costs to the community of the “do nothing” option.
(iii) Development of separate Management Plans to address each environmental degradation issue identified in the Catchment Plan, with a cost benefit analysis carried out on each management scenario.
The Upper Burrangong Catchment covers an area of 20,178 hectares, with the town of Young at its centre.
Figure 1: Location of Young, where the Upper Burrangong Catchment Plan is based.
The study area does not have a central river system but can be divided into three subcatchments. These are the subcatchments of Stony Creek, Burrangong Creek and McHenrys Creek. Downstream of their confluence, Burrangong Creek flows to Lake Cowal via the Bland Creek.
There are great pressures placed on the creeks around Young, which are associated with various land uses, particularly the expansion in areas planted to horticulture and vineyards in the catchment and in light industry located along the creek. The presence of exotics such as willows and silver poplars along Burrangong Creek and its tributaries has been of concern to Young Community Landcare Group. Pastures cover about 65% of the catchment area, crops about 10% and orchards about 8%. The urban area accounts for 3% of the catchment area.
The climate of the Upper Burrangong catchment is characterised by a dry summer and a cool moist winter. Average annual rainfall in Young is 654.4 mm with the most reliable rainfall from June to October. Winter rainfall events are the main contributor to groundwater recharge due to:
- winter rainfall pattern which is generally prolonged, of low intensity and increasing infiltration;
- cooler winter temperatures and less sunlight resulting in decreased catchment water use through reduced plant transpiration and evaporation losses (Bureau of Meteorology 1999).
Runoff from the catchment is most likely to occur in August and then expected on a recurrence interval of 2 years to the west of Young, 18 months around Young township and 12 months to the east of Young at Murringo (Hassall and Associates 1999).
The geology of the Upper Burrangong catchment is Middle Devonian Young Granite, which is characterised by high levels of granodiorite and gneissic granite (PPK Consultants 1999).
Previous studies indicate that groundwater trends in Young tend to follow topography, with the highest recharge zones occurring on hill crests while potential discharge zones occur along the major creeks and lower gullies. Groundwater levels in the Upper Burrangong catchment range from 24 metres below ground level to 0.4 metre below ground level (PPK Consultants 1999).
The dominant soil types in the Upper Burrangong catchment are rudosols, dermosols, chromosols, kandosols and sodosols. The red dermosols, or parnas and the red chromosols that occur on the crests and upper slopes are the main soil types on recharge areas in the catchment. The dermosols have been blown inland from the east and the south, while the chromosols have developed from the weathering of granitic rocks. The red colour of these soils indicates a high iron content, free drainage and the absence of a seasonally high watertable. These characteristics make them favourable soils for arable farming because they have good moisture retention and a relatively strong soil structure. Yellow chromosols and sodosols have formed on footslopes and drainage depressions on material that has accumulated from hillslope erosion and where salt has accumulated from subsurface water movement. The yellow subsoil colours indicate poor drainage. They are mainly erodible and less productive soils (Gardiner 1995; Isbell 1998).
The dominant vegetation communities in the catchment area are the Box Woodlands (Department of Land and Water Conservation 1999 draft). These communities have been greatly disturbed in the Upper Burrangong Catchment and it is rare to find a vegetation community in the catchment with all three storeys- tree, shrub and ground cover- present. Average tree cover in the catchment is 3.49%.
Water Quality of Streams
Young Community Landcare Group and Young Shire Council monitor water quality at eight sites in the catchment on a monthly basis. Both data sets indicate that nutrient concentrations and salt concentrations increase further downstream. Flow data from Department of Land and Water Conservation (2000) was used to calculate nutrient and salt loads exiting the catchment. The findings showed that 17.4 tonnes of salt as well as 26.7 kg of nitrogen and 7.5 tonnes of phosphorus leave the Upper Burrangong catchment each day.
The soils of the Upper Burrangong catchment are in the pH range of 4.4 to 4.6, which is moderately acidic (Parker, pers. comm. 2000). Soil acidity is estimated to affect 20% of crops and 80% of pastures in the Upper Burrangong catchment (Parker, pers. comm. 2000). This area totals 11001 hectares or 55% of the catchment area.
Aerial photo interpretation and field analysis identified areas affected by seasonal waterlogging. Piezometer and bore data was used to find areas affected by rising watertables in the catchment. Drainage depressions throughout the entire catchment area experience seasonal waterlogging due to high watertables. This area totalled 2103.2 hectares or 10.4% of the catchment area. Rising watertables lead to dryland salinity.
Soil salinity is generally caused by a number of factors, including rock type, soils, landform, rainfall, vegetation loss, land use and groundwater. Rock types associated with salinity are the Ordovician sediments and the Silurian granites, which contain stores of salt in their profiles. As water moves through these profiles, salts become mobilised and are transferred to the watertable.
The areas mapped showing signs of salinity in the Upper Burrangong catchment are drainage depressions where watertables have reached the surface, or areas where soil types change from well-drained red dermosols and chromosols to poorly drained yellow sodosols.
Currently, dryland salinity affects 1265 hectares, or 6.3% of the catchment. Urban salinity is estimated to affect 15% of the urban area in Young.
Sheet and rill erosion is more common on land used for cropping and horticulture under conventional tillage practices. A major source of sheet and rill erosion in the Upper Burrangong catchment is from unsealed roads with unvegetated table drains. Gully erosion has developed from concentrated runoff from steep areas in drainage depressions with little vegetative cover, as well as inadequate spillways of dams and stormwater outlets. Streambank erosion is severe in some stretches of Burrangong Creek, and has resulted from changes to stream morphology, riparian vegetation condition, stock access to streams and midstream vegetation such as willows and cumbungi. All forms of erosion cover an area of 4,160 ha or 20.6% of the catchment area.
Soil Structure Decline
Soil structure decline occurs on traditionally cultivated farming and orchard areas. Following aerial photo interpretation and extensive field studies, the area of the Upper Burangong catchment estimated to be experiencing soil structure decline is 4179 ha, or 21% of the catchment.
Native Vegetation Decline
It is now widely accepted that native vegetation represents an important resource that is useful for a range of conservation, land management and water quality issues. As well as severe land clearing, other reasons for native vegetation decline in the catchment are related to dieback and lack of regeneration. Natural regeneration is impeded by stock grazing, competition from introduced plants, soil compaction, altered nutrient levels and fire regimes, changes in soil water, loss of native fauna which assist in seed dispersal, germination and establishment and use of farm chemicals (Howling 1997). Land managers were still being advised by authorities to clear native vegetation as late as the 1960s (Tooth 1997).
Scientists and agronomists now recommend a minimum of 15% tree coverage on agricultural land (Howling 1997). In recent times the focus has shifted to establishment of windbreaks, fencing out and restoring remnant vegeattion, and strategic planting of trees and shrubs for erosion and dryland salinity control.
Average tree cover is just 3.49% of the catchment area. Natural regeneration is taking place in 65% of this area. An assessment of riparian vegetation condition in the study area showed that 68% of this vegetation is in either poor or very poor condition.
Weed infestation is widespread and nonselective in the Upper Burrangong catchment. However, generalisations can be made as to the preferential conditions of the major weeds:
- Paterson’s Curse (Echium plantagineum) is a strong competitor in pastures because of its large taproot
- Scotch Thistle (Onopordum acanthium) is a weed of pastures, roadsides and wasteland, which thrives in high fertility soils associated with pasture improvement.
- Phalaris (Phalaris aquatica) is an important pasture grass, but can be a problem where it is not wanted, in orchards for example.
- Paspalum (Paspalum dilatatum) is a weed of crops, citrus orchards and lawns.
- Couch (Cynodon dactylon) occurs in a variety of situations including gardens, vineyards and cultivations. It can also be an indicator of potentially saline areas.
- St John’s Wort (Hypericum perforatum) is also a particularly troublesome weed, especially in pastures where it can cause nervous disorders in stock.
- Blackberries (Rubus fruticosus) are weeds of riparian areas, as well as roadsides and pastures in cool, high rainfall areas.
- Dock (Rumex sp.) is a weed of orchards, irrigated crops, established pastures, lawns and wasteland. It can be an indicator of permanently wet areas.
- Spiny Rush (Juncus acutus) is an indicator of a permanently wet area that may also be saline.
- Sea Barley Grass (Hordeum marinum) is another pasture weed that acts as an indicator of saline soils.
- Cumbungi (Typha sp.) is an erect reed-like perennial which grows in stationary or slow-moving water. It is found in saline streams of the Upper Burrangong catchment, as well as on salt-affected land that is poorly drained.
Declining Riverine Corridor Health
The health of riverine corridors was assessed by the level of stream reach disturbance, bank condition, bed and bar condition, aquatic habitat, riparian vegetation, aquatic vegetation and scenic/recreation value.
An assessment of the creeks in the Upper Burrangong catchment rated the overall stream condition as moderate, with parts of the Burrangong Creek through Young township as very poor. Just 35.5 km or 20.5% of the total stream length in the catchment has tree cover.
Water Quality of Streams
It is difficult to quantify the costs of continuing poor water quality to the community over the next 30 years. However, it must be considered that water quality decline affects people living in catchments further downstream. Declining water quality results in reduced productivity of water dependant enterprises, both in town and in rural areas. Nutrient loading and growth of algal blooms restricts the uses of the water supply. Salinity mostly restricts irrigation, effects livestock health and impacts on water delivery systems.
Most soils in the Upper Burrangong catchment have a pH of between 4.4 and 4.6 which limits plant germination and growth for many commercial crops. Hassall and Associates (1999) estimated production losses from moderate soil acidity at $78.13/ha/year for the Weddin study area, of which the Upper Burrangong catchment is part. This totals $859,528 per year in lost production for the 11001 ha of the catchment affected by soil acidity.
Production losses from rising watertables are highly variable, but are estimated by landholders in the catchment to average a 70% loss per year. Assuming the weighted average annual gross production from sheep, cattle and grain is $100 per hectare per year, the total cost of rising watertables to the rural community in the Upper Burrangong catchment is $147,224 per year.
Hassall and Associates (1999) estimated production losses of $235.17/ha for Class III land and $18.50/ha for Class IV and V land. This totals an annual production loss of $276,978 due to dryland salinity in the Upper Burrangong Catchment. Road maintenance due to urban salinity problems in Young alone costs Young Shire Council $134,000 per year. Wagga Wagga Council (Short 1998) has estimated that the average cost of repairing damage to houses due to salinity is on average $10,000 per house. About 15% of the town of Young is estimated to be affected by urban salinity, thus facing this one-off cost in the future, which would total $4,559,235.
Soil loss presents a cost to the rural community in loss of productive land. Sheet and rill erosion was estimated to cost between $3.52 and $78.13 per hectare (Hassall and Associates 1999). Gully and streambank erosion has a cost of $13.88 per hectare to the community. The total cost of soil erosion in the Upper Burrangong catchment is $169,379 per year.
Soil Structure Decline
Research on the effects of a severe storm on a light-textured soil at Cowra showed that on a cropping paddock with poor soil structure, the storm eroded 342 t/ha, costing $230/ha in lost nutrients. On an adjacent paddock with better soil structure and more stubble cover the storm eroded only 65 t/ha and lost only $45/ha in lost nutrients (Butler 2000).
A cost benefit analysis in the catchment (Hassall and Associates 1999) shows that the costs of soil structure decline on average amounts to $28.24/ha/year. The total estimated potential cost of soil structure decline over 4179 ha of the catchment affected is $118,015 per year.
Native Vegetation Decline
It is difficult to quantify the total cost of native vegetation decline in the catchment. However, environmental and production returns from dryland eucalypt farm treelots in Northern Victoria have shown benefits valued at $100/ha/year. Absence of trees indicates this benefit is foregone.
Tree cover should aim at 15% as a minimum to maintain biodiversity (Howling 1997). As existing tree cover in the Upper Burrangong catchment is 3.49%, the remaining 11.51% of the unvegetated area (2322 ha) required to maintain biodiversity is valued at a loss of $232,248 per year.
Weed infestation is widespread across the Upper Burrangong catchment and reduces crop, pasture and orchard production. Local agronomists have estimated up to 75% yield loss for crops with no weed management in place worth an average yield reduction in the Young district of 50% (Thompson, pers. comm. 2000). The cost of weed infestation on crops in the catchment in terms of yield reduction can be averaged at $195/ha per year, a total of $322,530 per year.
The yield reduction caused by weeds in pastures is less, because they can provide a food source for livestock, even though it is of poor nutritive quality. Local agronomists have estimated up to a 75% production loss due to weed infestation, with an average carrying capacity reduction in pastures of 40% in the Young district (Thompson, pers. comm. 2000; Parker, pers. comm. 2000). Based on a current net return of $150/ha/year, depending on wool prices, losses of upt to $60/ha/year or $794,400 per year for the total area of pastures in the Upper Burrangong catchment.
Local agronomists have estimated that average yield reduction on orchards in Young due to weed infestation is 10% (Kennedy, pers. comm. 2000). Based on average yield of 3 tonnes of fruit per hectare at $5/kg (Coupland, pers. comm. 2000), production can reach $15,000 per year. A 10% yield reduction on the 1654 ha of orchards in the catchment is equivalent to a $2,481,000 loss per year.
The estimated value of average yield reduction due to weed infestation in the Upper Burrangong catchment is $3,597,930 per year.
Declining Riverine Corridor Health
The creek systems of the Upper Burrangong catchment perform the obvious and necessary task of draining the catchment. They have an added potential value in providing the backdrop to many of the town amenities and potentially to its scenic value. In their current degraded condition, this potential value is largely unrealised. This is in marked contrast to the clean and attractive recreational facilities that these creeks provided until the mid 1950s. The financial loss in terms of tourism, unrealised land value increases and damage to urban infrastructure is considerable but not costed here.
The areas affected by each of the degradation issues identified by the Young community has been determined through a process of aerial photograph interpretation and GIS assessment.
There will be current and future costs to the community as a whole if management plans are not put in place to address these degradation issues in order to rehabilitate the catchment.
Land and water degradation issues in the Upper Burrangong catchment costs the community as a whole approximately $4,559,235 as a one-off payment to maintain houses and buildings affected by urban salinity, $5,535,302 per year in lost production, as well as uncosted financial losses.
Bureau of Meteorology (1999). NSW Regional Office, Climate and Consultancy Section.
Butler, B. (2000). Managing Soil Structure. In Lachlan Soil Management Guide. Project funded by the Natioonal Landcare Program, March 2000.
Coupland, S. (pers. comm. 2000). Orchardist- E.F. Cunich and Co., Cowra Road Young
Department of Land and Water Conservation (1999 draft). Mid-Lachlan Regional Vegetation Management Plan: Draft for public exhibition. March 1999.
Department of Land and Water Conservation (2000). Stressed Streams Assessment of the Lachlan Catchment. April 2000.
Gardiner, T. (1995). Land management options to control dryland salinity on highly acidic soils. Department of Land and Water Conservation.
Hassall and Associates (1999). Weddin Catchment Action Plan. Department of Land and Water Conservation.
Howling, G. (1997). Remnant Vegetation Strategy for the Central West Catchment. Central West Catchment Committee, Orange NSW.
Isbell, R.F. (1998). The Australian Soil Classification. CSIRO Publishing.
Kennedy, P. (pers. comm. 2000). Agronomist, Chandlers IAMA, Lovell Street Young.
Parker, P. (pers. comm. 2000). District Agronomist, NSW Agriculture Young.
PPK Consultants (1999). Groundwater Assessment for Effluent Reuse Young NSW. Department of Public Works and Services.
Short, B. (1998). Impact of Urban Salinity and Waterlogging in Wagga Wagga- The No Plan Scenario- A scoping study. Department of Land and Water Conservation June 1998.
Thompson, F. (pers. comm. 2000). Agronomist, Thompson’s Rural Supplies, Boorowa Street Young.
Tooth, I. (1997). The Ben Chifley Dam Catchment Action Plan. Department of Land and Water Conservation, December 1997.