December 2017 Tamar Estuary
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- Bu səhifədəki naviqasiya:
- Balanced investment options
- Dairy
Tamar Estuary River Health Action Plan 23 levels in stormwater that is directly discharged into Tamar Estuary Zone 1. Works have recently been undertaken in the Kings Meadows Rivulet catchment to resolve these issues resulting in significant and measurable improvements in pathogen levels observed. It is considered that continuing these works to address issues in Trevallyn and Waverley/Ravenswood stormwater systems would have material benefits. 4.5
Findings The full cost of implementing the actions considered by the Working Group across the catchment was estimated at $117 million. Three different investment budgets were then considered: $2 million; $5 million; and, $10 million 1
budgets. These budgets were allocated to the individual land uses one at a time to allow comparison of the cost effectiveness of various investments. The location of investments was prioritised by the criteria above, with grazing and urban action focused first in the North Esk and Upper Tamar foreshore catchments before investments above Trevallyn Dam were considered. It was found that all dairy actions considered could be implemented catchment wide for $1.1 million, less than the lowest budget considered. Addressing issues with the separated stormwater system was also costed at $500,000 for both Trevallyn and Waverley/Ravenswood systems and so would be fully implemented for 25 per cent of the lowest budget considered. The analysis shows very clear differences between the cost effectiveness of the different actions in reducing greater TEER catchment loads 2 and to a lesser extent Tamar Estuary Zone 1 concentrations 3 .
Dairy management was by far the most cost-effective action in reducing greater TEER catchment pathogen loads, accounting for more than 50 per cent of the potential load reduction possible from all considered actions at under 1 per cent of the full cost (see Figure 5). Investments in dairy management also had similar impacts on nutrient and sediment loads as a $5 million investment in grazing management, for around only a fifth of the cost. Investments in water sensitive urban design (WSUD) are very cost ineffective for reducing greater TEER catchment loads with significantly smaller proportions of load reduction versus relative costs. Addressing issues with sewage intrusion to Launceston’s separated stormwater system (SS) is cost effective for enterococci but has no impact on nutrient or sediment loads. This option has a small overall impact on Greater TEER catchment loads but this impact compares favourably with an even smaller relative cost.
1 Note that with the exception of works to fix sewage intrusion into Launceston’s separated stormwater system, investment options assume a 15 per cent overhead to cover costs associated with program implementation such as extension staff. 2 Load is estimated in the model as the average concentration of pathogens, measured in colony forming units (cfu) across the catchment, multiplied by volume entering the catchment. 3 Concentration is the number of cfu per 100 millilitres of water at a specific point in the Estuary. Tamar Estuary River Health Action Plan 24
investment Options Differences between grazing and dairy management are less evident when their impact on Tamar Estuary Zone 1 concentrations is considered (see Figure 6). In this case it is modelled that all levels of investment in grazing management achieve greater decreases in Tamar Estuary Zone 1 concentrations for all pollutants than dairy management does. However dairy management impacts on enterococci concentrations are still high and compare very favourably to grazing, particularly given the smaller relative budget. Addressing issues with sewage intrusion into Greater Launceston’s separated stormwater system (SS) is a very cost-effective way of reducing pathogen concentrations in Tamar Estuary Zone 1, although this action has no benefits in terms of nutrient or sediment concentrations. This action achieves a greater reduction in pathogen concentration relative to cost than both dairy and grazing management. Water sensitive urban design (WSUD) is shown to be cost ineffective for addressing pathogen concentrations in Tamar Estuary Zone 1. Its greatest relative benefit is in addressing sediment concentrations which are not a focus in this Investment Plan. Even for sediments it is less cost effective than investment in either dairy or grazing management.
Tamar Estuary River Health Action Plan 25
investment options 4.6
Recommendations and expected benefits Balanced investment options Based on the above analysis, a set of balanced investment options has been developed, using a mix of investment in the different land uses with different levels of investment to maximise public health outcomes at those budget levels. These options include a mix of dairy management, grazing management and investments in reducing sewage intrusion into Launceston’s separated stormwater system. No investment in water sensitive urban design is included given it was found not to be cost effective for reducing pathogen concentrations in in Tamar Estuary Zone 1. The budget for planned investment for activities by land use for the three balanced investment options is given below. Catchment Action $2 million $5 million $10 million Dairy Brumbys-Lake, Macquarie, Meander & Tamar $550,000 $825,000 $1,100,000 Grazing North Esk $1,250,000 $1,330,000 $1,330,000 Upper Tamar $0 $1,660,000 $1,660,000 Brumbys-Lake, Meander & South Esk $0
$685,000 $5,410,000 Urban Launceston sewage stormwater intrusion $200,000 $500,000 $500,000
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