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Critical ecological assets in areas of high salinisation hazard in the Tasmanian Midlands

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Davies, PE and Barker, P (2005) Critical ecological assets in areas of high salinisation hazard in the Tasmanian Midlands. Project Report. DPIWE, Tasmania.

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Abstract

A GIS-based assessment has been conducted to identify ecological assets in high
salinisation hazard areas in the NAP region of the Tasmanian Midlands. Relative hazard
to aquatic ecosystems, wetlands, water bodies and streams, as well as to vegetation
communities from salinisation was evaluated. The hazard analysis was based on the
presence of particular groundwater flow systems, and on rainfall and vegetation
clearance. Hazard ratings were applied to these factors, and then to mapped polygons
describing each asset type by GIS overlay. Rule sets were applied to attribute each asset
polygon or streamline with an integrated hazard rating. High hazard ratings were
combined with information on asset features (e.g. wetland size, the presence of threatened
species etc) to develop a prioritised list of ecological assets in high salinisation hazard
areas.
148 wetlands (15% of the total) were rated as occurring in areas of highest hazard. 45 of
these wetlands and two water bodies were rated as occurring in areas of highest hazard
and being of high priority for management and/or monitoring. Around 7 - 8% of all
stream sections in the study area (ca 1 100 km) were rated as occurring in areas of high
hazard at low and median flows. These were primarily small headwater catchments of
several smaller river, creek and rivulet systems; and small floodplain or valley floor
tributaries of the lower Coal and Jordan and middle South Esk Rivers. Field evaluation
confirmed that high levels of stream salinity at baseflow were related to high hazard
ratings.
Relatively small areas of priority vegetation (848 ha) or numbers of threatened species
(100 populations) were located in areas of highest hazard. Only four of the highest
priority vegetation types (endangered/rare) were in the highest hazard category - lowland
Poa and Themeda native grasslands, Eucalyptus ovata forest and woodland, and riparian
vegetation. There are seven vulnerable communities occurring in areas of highest hazard,
with only inland Eucalyptus amygdalina forest with more than 50 ha in high hazard areas.
Critical Ecological Assets
v Davies and Barker
In comparison, relatively large areas of cleared agricultural land occur in areas of highest
hazard (39 139 ha).
Three groundwater flow systems were recognised as posing high salinisation hazard.
These were local scale systems in alluvial plains, floodplain alluviums and deeply
weathered sediments. Alluvial plain and floodplain alluvial systems account for the
greatest proportion of ecological assets located in areas of highest hazard. Field
assessment indicated that local systems in dunes are significant local sources of surface
salinity and should be further evaluated.
Recommendations are made with regard to future work, monitoring and assessment of
asset condition.

Item Type: Report (Project Report)
Keywords: salinisation, freshwater, Tasmania, vegetation, GIS, salinization
Publisher: DPIWE
Date Deposited: 28 Nov 2006
Last Modified: 18 Nov 2014 03:12
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