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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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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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