Fabric curtains stretch across the huge Warragamba Dam to trap ash and sediment expected to wash off wildfire-scorched slopes and into the reservoir that holds 80% of untreated drinking water for the Greater Sydney area.

In Australia’s national capital of Canberra, where a state of emergency was declared on Friday because of an out-of-control forest fire to its south, authorities are hoping a new water treatment plant and other measures will prevent a repeat of water quality problems and disruption that followed deadly wildfires 17 years ago.