Managing the impact of bushfires on water

Thursday, 16 January, 2020

Australia has seen a devastating start to the 2019-20 bushfire season which began in September, with separate fires extending across all states almost concurrently. This has resulted in the tragic loss of lives, homes, giant trees, native animals, pets, livestock and more. It has also required a massive national and international team response including firefighters, volunteers and the army. Fires are still burning around the country, and alarmingly, the fire season is expected to continue until at least April.

Our thoughts and prayers go out to the families and friends of those lost to the fire, and the many people, businesses and communities devastated by the impact of this season’s disaster. The professional contribution and sacrifice of everyone involved has been outstanding and we extend our sincere appreciation to them all.

Although bushfires are an intrinsic part of the Australia’s environment, we face new challenges and threats as our country becomes warmer and drier than ever before. The Bureau of Meteorology’s Annual Climate Statement for 2019, shows that Australia’s average mean temperature for the year was 1.52 °C above average, making it the warmest year on record since consistent national temperature records began in 1910. The same data also shows that ten of Australia’s warmest years have occurred since 2013. In addition to this, the national average rainfall total in 2019 was 277 mm, the lowest since consistent national records began in 1900.

With this is mind, Australia’s water sector is coming together to manage the imminent impact of the fires on water catchments, rivers, water supply, water quality, and infrastructure, and also to  prepare for such extreme events in the future.

“Our understanding of the risks and consequences needs to change,” said ICE WaRM Managing Director, Darryl Day.

“We don’t yet know the full extent of the effects of bushfires that have increased in intensity and frequency and that are more widespread and concurrent. So we require greater capacity, more research and significant investment in tools and infrastructure, as we prepare for a likely increase in extreme events with climate change. Modelling the risks may also help us in our planning.”

Meanwhile, water businesses are currently responding to the crisis with great professionalism and collaboration as they restore supplies for communities and critical human needs.

The water supply for Sydney was already at a record low, with the lowest inflow over the last 33 months into the largest source, the Warragamba Dam, on record. According to Water NSW (New South Wales State), this record low inflow was less than half the previous lowest water inflow which occurred between 1939 with 1941.Sydney Water has been running the desalination plant since July 2019 which provides ~15% of the city’s demand, or 250 ML/day and plans are being fast tracked to double this capacity.

With heavy rain forecast over the next few days, the battle is on to manage the water quality as a result of extensive fires in the catchment. Over 320,000 hectares has been burnt around the catchment and the ABC has reported that the State Government was racing to raise curtains and install booms to prevent silt and ash from contaminating the water at Warragamba Dam.

Rain washing ash into waterway – Image courtesy ABC (supplied by David Menzel)

“In the short term, previous research has shown that there is a high likelihood of water quality deterioration when fire impacted soils and fire retardants are mobilised by rainfall events,” said Dr Peter Wallbrink (Director ICE WaRM).

“These mobilised soils and sediments also contain attached nutrients such as Phosphorus which can cause unanticipated and unwelcome effects on downstream reservoir nutrient levels.”

In the Murray Darling Basin the attention has also been on the impacts of water quality, with deteriorating conditions expected from rain washing ash and sediment into the streams, rivers and dams. Alerts are already in place for outbreaks of blue-green algae impacting water quality and the ecology, and the Murray Darling Basin Authority is coordinating operational responses with state water agencies. There is also much concern that these algal blooms will result in dangerously low oxygen levels, threatening aquatic life including Australian fish species and freshwater turtles.

During the decade long “Millennium Drought” Australia faced considerable water security challenges and actively invested in research into basin planning and management, tools and data generation as well as community engagement, and has shared these learnings with the world. Again, Australia appears to be at the forefront of how hydrology, (and associated extreme events such as bushfires) may be affected by climate change.

Understanding and contributing to the role of Australia’s water sector in addressing these challenges will be a prominent focus for ICE WaRM as we follow our nation’s journey and share learnings with the rest of the world. Stay connected for more in future newsletters.