Now you see them: will the ephemeral lakes of Namadgi National Park be lost to climate change?

Lakes occur where drainage is disrupted by any cause which blocks drainage lines, creating closed basins or damming streams. These causes include tectonism and faulting, volcanic eruptions and lava flows, or simpler build up of sediments to form barriers by the sea, rivers, dunes or biota. The water bodies can be permanent, intermittent or ephemeral, often reflecting the balance between precipitation, catchment size and evaporation. As such they are valuable monitors of the general availability of water in landscapes and of long-term changes in climate. The steep slope and mature landscapes of Namadgi National Park in the Australian Capital Territory (ACT) provide little natural scope for lakes even though Canberra lies near some fine examples of fault-dammed lakes such as Lake George. There are, however, several shallow lakes and ponds between 20-125m in diameter in the ACT mountains which reflect the climate and geology and which have not been described or researched. Their age and causation are not well understood and they are not shown on maps due to their small scale and ephemeral nature. However some are well known to bushwalkers. This paper describes the lakes and postulates possible reasons for their siting and persistence. I have been able to observe these lakes during regular inspections of ecological monitoring sites and while mapping the ACT peatlands (Hope et al 2009). The reasons for the persistence of these lakes in Namadgi, when they appear to be absent from neighbouring Kosciuszko National Park, may provide a guide for their likely continuation under conditions of climate change.