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Variously, submissions linked sedimentation build up to poor public health outcomes, poor ecological health and a
lack of recreational amenity. However, the amenity issues seem to be a key priority for the community.
Proposals to deal with sedimentation have included:
Making changes to Estuary bathymetries;
Moving the Tailrace discharge to Yacht Basin;
Returning higher flows from Trevallyn Dam to the South Esk;
Changing the configuration of North Esk entry at the confluence of the Upper Tamar;
Upstream detention basins;
Alternatives to silt raking;
Establishing a barrage; and
Implementing speed limits on boats to stop riverbank erosion.
On the basis of the strength of support in submissions for improving sediment based amenity issues, the
Taskforce determined that it would be appropriate to seek appropriate technical advice to peer review proposals
put forward. The process for this work is documented in section 10.
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4.
Catchment Action Working Group
4.1
Membership
The Taskforce Catchment Action Working Group consisted of members from Dairy Tasmania (Jono Price and
Rachel Brown), the Tasmanian Farmers and Graziers Association (Peter Skillern, Brigid Morrison and Nick Steel),
the Environment Protection Agency (Martin Read and Glen Napthali), the Meander Valley Council (Martin Gill),
the West Tamar Council (Rolph Vos) and NRM North (Rosanna Coombes), with technical and scientific
modelling support provided by isNRM (Dr Rebecca Kelly).
However, the Group’s Technical Report and the proposed Investment Plan (see Appendix 2) also benefited from
review by the TEER Scientific and Technical Committee and Partnerships Committee.
4.2
Previous work available and updates completed
The Catchment Action Working Group’s efforts build on the work previously undertaken in development of the
TEER Water Quality Improvement Plan 2015 (WQIP) by NRM North for the catchment. The Technical Report
and Investment Plan are a considerable step forward in the WQIP implementation for the Zone 1 area.
The WQIP and Investment Plan consider the impact of investment actions on four major pollutants: Total
Nitrogen (TN); Total Phosphorus (TP); Total Suspended Sediments (TSS); and enterococci. TN and TP are
nutrients. Elevated nutrient levels can feed the growth of nuisance algal growth in streams, dams and estuaries.
This algae can increase turbidity and can smother and replace native plant and animal species. It can also make
water dangerous for recreation and drinking.
High levels of TSS make water turbid and dirty looking and can smother and replace native plant and animal
species, decreasing the health of waterways. Sediment exports from the freshwater system to the Estuary can also
contribute to sediment accumulation in the Upper Estuary.
Enterococci is a bacteria used as an indicator of pathogen pollution. Pathogens come from animal or human faeces
and when elevated can make people sick if they drink or recreate in water.
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The Tamar Facts document (Appendix 1) and the Catchment Action Working Group Technical Report and
Investment Plan (Appendix 2) both provide a more detailed discussion and breakdown of the specific sources of
these pollutants within the Tamar catchment, but the following figure summarises the catchment by land use and
the contribution of those land uses to catchment flow and pollutants.
Figure 3. Relative contribution of different land uses to Greater TEER catchment loads, flows and area
As can be seen, dairy and grazing represent the largest contributors of enterococci and hence are the focus of the
Group’s proposed Investment Plan, though contributions from urban areas too are not insignificant.
4.3
Criteria for investment plan
The Catchment Action Investment Plan considers the range of actions evaluated and recommended in the TEER
WQIP 2015. From these, a smaller group of actions were selected for consideration using the following criteria:
High leverage – actions must have a large relative impact on pollutant loads
Adoptable – feedback from key stakeholders must indicate that actions can be adopted at sufficient levels
with incentives
Measurable – actions in the Investment Plan need to be able to be accounted for within a planning and
investment cycle
Actions considered target pollutants coming from dairy, grazing and urban areas. These land uses are the three
largest contributors to pathogen loads in the greater TEER catchment and are major controllable sources of
nutrient and sediment loads (i.e. loads that are able to be reduced through improved management actions as
opposed to loads that are largely driven by uncontrollable factors such as rainfall and high slope).
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4.4
Actions considered
The figure below shows the range of actions for each land use considered in the WQIP and the actions selected
using the above criteria for assessment in this Investment Plan.
Figure 4. Catchment actions considered to target Estuary enterococci levels
In dairying, improved effluent management has great potential. While a Code of Practice established under the
Dairy Industry Act 1994 currently guides the size of the holding pond required for effluent, there are further
management measures associated with treatment and spreading that could be improved.
In the case of both dairying and grazing, there is much that can be done in limiting stock access to streams
through fencing and provision of off-stream water as well as through addressing issues with stock crossings.
Incorporation of a 5m wide vegetated riparian buffer within this fencing will also be of much benefit in grazing.
With respect to the actions in urban settings, large scale water sensitive urban design such as wetlands, swales
and bioretention systems focused on treating urban runoff to remove pollutants as well as reducing runoff
volumes can be more widely utilised.
In addition, fixing issues with sewage intrusion into Launceston’s separated stormwater system also has merit.
This action was not identified in the 2015 WQIP but was included in the analysis for the Working Group’s
Investment Plan following the success of a recent program run by the Launceston City Council. This program
found sewage intrusion into the separated stormwater system in parts of Launceston is causing elevated pathogen
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