National Wetlands Update September 2012
Issue No. 21, September 2012
Little Waterhouse Lake Ramsar site - of droughts and flooding rains
Peter Newall, Independent Ecological Consultants; Lance Lloyd, Lloyd Environmental Pty Ltd; Department of Sustainability, Environment, Water, Population and Communities; Emma Williams, NRM North
In 2009, NRM North, with funding from the Department of Sustainability, Environment, Water, Population and Communities, commissioned Lloyd Environmental to produce an Ecological Character Description for the Little Waterhouse Lake Ramsar Site, Tasmania.
The project was able to observe the site towards the end of the Millennium Drought and after the drought had broken.
Little Waterhouse Lake is a Ramsar listed coastal freshwater lagoon on the sand plains of north-east Tasmania. The site has a range of habitat types including a large area of open water, intermittently flooded meadows, sedge marshes and a permanent area of peatland, all combining to support a highly diverse macrophyte flora.
The site also supports two regionally rare wetland plants (river club sedge and sea club-rush), a regionally vulnerable fauna species (white-bellied sea eagle) and two nationally vulnerable fauna species (green and gold frog and dwarf galaxias).
The lake's high floristic diversity (45 species of aquatic and semi-aquatic plants) and high habitat diversity is dependent upon fluctuating water levels which support large areas of intermittent wetlands.
A dramatic change of water levels in the lake was observed in November 2009, following a 10 year drought. Heavy rains during September 2009, provided a much needed reinjection of water, organic matter and significant biological activity to the site. As well as supporting the sustainability of the wetland plants over the medium-term, the higher water levels were accompanied by an almost immediate, large increase in numbers of young fish (Galaxias sp.) and a diverse and abundant macroinvertebrate fauna.
The observations of the site during drought and flood highlighted the importance of recognising wetlands as biological mosaics in time as well as in space. The breaking of a 10 year drought with an unusually large flood also highlighted the importance of considering the temporal mosaic beyond seasonal, to yearly and even decadal variation.
This has important implications for assessment of ecological character, as the extremes of the site's ecological condition could be easily overlooked yet may contribute substantially to its ecological function, habitat diversity and biodiversity.
For further information visit Little Waterhouse Lake.
Mosaic of wetland habitat types at Little Waterhouse Lake Ramsar Site. (Peter Newall)