As forests burn worldwide, drinking water is at risk
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.
There have not yet been major impacts on drinking water systems in southeast Australia from the intense fires that have burned more than 40,000 square miles since September. But authorities know from experience that the biggest risks will come with repeated rains over many months or years while the damaged areas recover.
And because of the size and intensity of the fires, the potential impacts are not clear yet.
The situation in Australia illustrates a growing global concern: Forests, grasslands and other areas that supply drinking water to hundreds of millions of people are increasingly vulnerable to fire due in large part to hotter, drier weather that has extended fire seasons, and more people moving into those areas, where they can accidentally set fires.
More than 60% of the water supply for the world’s 100 largest cities originates in fire-prone watersheds — and countless smaller communities also rely on surface water in vulnerable areas, researchers say.
When rain does fall, it can be intense, dumping a lot of water in a short period of time, which can quickly erode denuded slopes and wash huge volumes of ash, sediment and debris into crucial waterways and reservoirs. Besides reducing the amount of water available, the runoff also can introduce pollutants, as well as nutrients that create algae blooms.
What’s more, the area that burns each year in many forest ecosystems has increased in recent decades, and that expansion likely will continue through the century because of a warmer climate, experts say.
In this Jan. 7, 2011, file photo, water flows from a water fountain at the Boys and Girls Club in Concord, N.H.