Kamarooka Case Study Catchment, Victoria
Kamarooka is about 35 km north of Bendigo in north-central Victoria. The catchment is predominantly extensive dryland pasture for sheep grazing interspersed with cropping. It has low permeabilities and moderate to low gradients, and a low ability to move groundwater. Similar local groundwater systems are widespread in the lower slopes of the western side of the Great Dividing Range and on the Lachlan Fold Belt (New South Wales).
Approximately 800 ha of this catchment is affected by salt. Of this, 70 ha were considered to be severely affected in March 2000 (salt seeps and no plant growth).
Figure 21.Distribution of local groundwater flow systems in fractured rocks or weathered fractured rocks.
Results of groundwater investigation and modelling
- If the current land use is maintained, the area of shallow water tables (and salinity) will continue to expand laterally along the break of slope, but will not expand uphill; an extra 1% of the catchment is likely to be affected.
- If changes are made to land use in the catchment to reduce recharge by 50%, water tables can be expected to fall within 100 years, resulting in a slight reduction of the salt-affected area.
- A 40% decline in the area of land affected by shallow water tables can be expected within 50 years, and its elimination within 100 years if a 90% reduction in recharge can be achieved as a result of extensive changed land use.
Implications
- A large reduction in recharge is required to markedly reduce the area of shallow water table and salinised land, but this is expected to be achievable through a combination of revegetation and the introduction of improved farming systems.
- The main aquifer is fractured rock, which makes engineering solutions like groundwater pumping difficult to implement. Surface drainage is also likely to be unsuccessful because the fractured rock aquifer is very deep and the surface material is very clayey (low permeability).
A full technical report is available on the Audit's Australian Natural Resources Atlas.
Figure 22and Table 21.Kamarooka (Victoria): change of area at risk in response to different recharge reduction rates - based on current recharge rate.
|
Recharge Reduction |
|||
|
Year |
No change (%) |
50% |
90% |
|
2000 |
10 |
10 |
10 |
|
2020 |
11 |
11 |
10 |
|
2050 |
11 |
10 |
6 |
|
2100 |
11 |
9 |
0 |
CAPACITY TO CHANGE - Kamarooka case study of dryland salinity and watertable control
Kamarooka catchment, located in north-central Victoria on the northern slopes of the Great Divide. Salinity impacts within the Study Area appear mainly on farmland along the 'break-of-slope'. At present 7 per cent of the catchment is salinised and CSIRO believes that, even without further management, this has now stabilised.
Background
The analysis compared the benefits and costs associated with salinity control in Kamarooka catchment being one of four contrasting case studies (Lake Warden, Upper Billabong, Wanilla). The approach adopted was to take estimates of the physical scale of impacts for each type of damage caused by dryland salinity (e.g. area of agricultural enterprises, number of stream diverters, kilometres of roads affected, number of species affected), and to apply damage functions for each of those types of impact. Data describing the physical scale of impacts have been captured using mainly GIS layers which describe the location of dryland salinity in each case study catchment. The damage functions developed for the purposes of quantifying the economic impacts of dryland salinity are for: agriculture and commercial forestry; roads and rail; urban centres; water users; and environmental values.
Key findings
- For the Kamarooka catchment (Vic), it was concluded that a continuation
of the current recharge rate would not result in significant change in the
area of salinised land. At present, 7 per cent of the catchment is salinised
and CSIRO modelling suggests that, even without further management, this has
now stabilised. This is primarily because of the substantial amount of salinity
control that has already been implemented.
- For a further 50 per cent reduction in recharge at the top end of the catchment,
achieved by replacing all annual pasture with lucerne in the pasture phase
of the rotations, CSIRO's modelling predicts a 50 per cent reduction in the
area of land at risk of salinisation within 20 years and a further reduction
to 2 per cent of the catchment within 100 years. It has been estimated that
this would lead to an increase in the discounted value of agricultural incomes
by about 40 per cent. That is, the results indicate that is economically viable
to adopt the recommended farming system option.
- For a 90 per cent recharge reduction option at the top end of the catchment,
achieved by tree planting over 80 per cent of the top of the catchment, there
would be a 70 per cent reduction in the area of land at risk of salinisation
within 20 years, with its complete elimination within 100 years. The 90 per
cent reduction in recharge proposed by CSIRO would reduce farm incomes, even
though the tree planting would eliminate the risk of salinity for Kamarooka
within 100 years.
- Lucerne is well suited to North Central Victoria, unlike some of the highly
salinised areas of Australia, and it is profitable for farmers to grow lucerne
plus the benefits of reduced salinity are a bonus that comes with lucerne
adoption. It seems that landholders have accepted the message that lucerne
represents an appropriate salinity control. Approximately 20 per cent of perennial
pastures in the catchment presently comprise lucerne in most seasons. The
consultants discussed the pros and cons of lucerne adoption with landholders.
The common views appeared to be that it had been necessary to plant lucerne
for salinity control, but that they would not be expanding their production
of lucerne.
- Radical changes to farming systems are required to incorporate lucerne,
particularly when managed to suit the dual objectives of maximising farm incomes
and maximising recharge reduction. Experience has shown time and time again
that radical changes to farming systems in Australia have occurred only when
there are very substantial additional farm incomes to be gained, or very substantial
costs to be avoided (see Section 5.3 of project report).
- In the Kamarooka region there is little likelihood of an expansion of the existing extent of salinity. The existing salinity damage is recoverable over a century with the replacement of annual pastures with lucerne pastures. The local farm community has already undertaken extensive planting of dryland lucerne. However, further planting will be mediated by the relative returns of cropping and grazing enterprises. At present, and for the foreseeable future, it is likely that cropping will remain more attractive. In the longer term, there is reason to question the extent to which farming will remain a dominant land use in this district.
Lessons learnt from all salinity case studies:
- There is no simple broadly applicable paradigm with which to conceive our
responses to salinity.
- Expectations of farm based change leading to salinity control need to be
tempered.
- Broad scale reforestation proposals will often be poor investments from
an economic and social perspective.
- A lack of profitable technically feasible options is the major constraint
to the capacity to control salinity.
- The major issue of "capacity for change" is the capacity of our
community to make informed decisions about investment in salinity control.
- We need to re-engineer our integrated catchment management structures to
operate within an adaptive management framework.
- Investment in salinity control should be based upon a triage model.
- A "works on the ground now" imperative should be tempered by a
"least regrets" investment approach.
- Landscape change must be seen as a multi-generational challenge.
Further Information
the technical reports:
Please Note: PDF files are in Adobe Acrobat Version 4.0 format. You will need a copy of an Acrobat Reader in order to view them. Blind and visually impaired users can view.pdf files using a tool available on-line from Adobe Systems that converts the.pdf files on the fly to HTML.
- Assessment of Salinity Management Options for Kamarooka, Victoria: Groundwater and Crop Water Balance Modelling in PDF format (11.9 MB)
- Capacity to change - Case studies of dryland salinity and watertable control by Mike Read. PDF format (1.2 MB)
- Capacity to change - Case studies of dryland salinity and watertable control - APPENDICES by Mike Read. PDF format (1.9 MB)
- Structural Change in Australian Agriculture: Implications for Natural Resource Management: Salinity case studies by Neil Barr. PDF format (1.3 MB)
Table of Contents for the Australian Dryland Salinity Assessment 2000
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