BUSHFIRES AND URBAN WATER SUPPLIES

As the bushfires continue to burn around the state there is an increasing realisation that another very likely impact of these widespread fires is contamination of urban water supplies. This happened  to Canberra’s water supply  following its devastating  2003 bushfires and has happened  in other places where dam catchments have been severely burnt.

It happened recently to Tenterfield’s water supply.  Before the bushfires its water supply had been under stress because the dam level had dropped in October to about 18% and residents had been advised to boil their water.  A storm late in November topped up the dam but damaged silt traps designed to prevent sediment entering the dam.  Massive amounts of ash and debris from the recent bushfires were swept into the dam.

According to Stuart Khan, a water security expert from the University of NSW, a combination of events have created Tenterfield’s problem.

“First of all you’ve got a drought which means the catchment is very dry,” he said.   “It also means the reservoir level is very low and there’s no opportunity to dilute new flows that come in.”

“Fire followed by heavy rain will wash ash into waterways.  There’s a lot more erosion because you don’t have the trees and roots holding the ground together.  Having a reservoir full of soil and sediment and ash is in itself a real problem because it makes water treatment processes more difficult.”

Water quality impacts can include deoxygenation and the growth of cynobacteria, which can be toxic.

He also pointed out that a lot of towns in NSW “don’t have the resilience in their drinking water supplies to get through these sorts of scenarios.”

There are now concerns for Sydney’s water supply because of fires burning in the Lake Burragorang catchment.  This lake sits behind Warragamba Dam and accounts for 80% of Sydney’s water supplies.

In relation to Sydney’s situation Stuart Khan  is concerned about the impact of heavy rain in the catchment . He said, “The best case is we get gentle rain for weeks and months that allows some gentle regrowth.”

            Leonie Blain

his article was originally published in the VOICES FOR THE EARTH column in The Daily Examiner on December 23,  2019

A FIERY FUTURE - PART 2

In "A Fiery Future - Part 1"  conservationist Dailan Pugh described the impact of the current bushfires on rainforest, with particular reference to Terania Creek. Below is a continuation of that post which was  published in the CVCC blog on December 4.

As exemplified by Koalas, numerous species have been hit hard. The fires have burnt out 23% of the high quality Koala habitat identified in north-east NSW, including a third of that on public lands. Only small refugia have survived within the burnt areas, and the Koalas are under immense stress in these.

Though the situation is more dire than indicated as much of the highest quality habitat has been degraded by intensive logging, and most of the remaining core populations have now been hit hard by the fires.

The Busby's Flat and Myall Creek fires have burnt out most of the regionally significant Koala populations of the Richmond Lowlands, the Bees Nest and Liberation Trail fires burnt out the most of the nationally significant Koala populations on the Dorrigo plateau, and the Crestwood Drive fire burnt out the major refuge left south of Port Macquarie.

While the rednecks are quick to blame national parks for fires, parks only represent 36% of the burnt area, with private lands 44%, and most of the ignition is likely from humans. Given that logging dries forests, creates fuel and increases the likelihood of canopy fires it is the bigger threat.

There is a belief that we need to burn forests more frequently to reduce fire threat, though it only takes 2-4 years for leaf litter to build up, and in extreme events prescribed burning does little to stop the spread of fire. It is telling that 151,000 ha of the area burnt this year has been burnt in either wildfires or prescribed burns in the past 3 years, with 73,000 ha burnt in the previous 12 months.

As well as affecting rainforest and old growth trees, too frequent burning adversely affects many seed producing shrubs, along with refuges and resources for a variety of fauna.

The protection and expansion of forests are essential to take up and store the carbon we emit if we are to have any chance of limiting the worst of climate heating. As we continue to slash and burn our forests we are increasing their flammability and turning a vital carbon sink into another source of emissions.

We need to undertake a rigorous review of how we manage forests, manipulate fire and protect property if we are to adapt to this brave new world we are creating. Business as usual is an unfolding catastrophe.

   -  Dailan Pugh 
       November 2019.

A FIERY FUTURE - PART 1

Hundreds of ancient Brush Box and other rainforest trees, many over a thousand years old, have been felled in the head of Terania Creek, their bases eaten out by fire. While the loggers were stopped 40 years ago, this time nothing could stop the assault by human-induced climate change.

In early November fire swept into the basin at the head of Terania Creek, consuming ferns, desiccating shrubs and cooking thousands of Bangalow Palms. Towards the valley floor the remnant moisture slowed the fire's assault, though the fire ate at the tree's bases, toppling immense trees that smashed through the rainforest canopy, spreading the devastation. Three weeks later fallen veterans were still smouldering and fire trickled through the leaf litter deep in the rainforest.

The last time fire burnt into the heart of this rainforest was around 1,100 years ago. Now we have so fundamentally altered the climate that a regime change is occurring and such events will happen with increasing frequency.

From August to November this year the Rural Fire Service (RFS) mapped 1.7 million hectares of north-east NSW, from the Hunter River to the Queensland border and west onto the tablelands, as being burnt in wildfires. So far 958,000 ha of public lands and 752,000 of private lands have been affected.

The scale is already massive, encompassing 20% of the land area, and 32% of our remnant native vegetation, and at the time of writing the fires are expected to continue for months.

The fires are coming on top of a drought, compounding each other's impacts.

The bush is so dry that fire is burning through the moist areas, the gullies and rainforests, that we could rely upon in the past to stop fire's spread. These are also the refugia that so many of our species depend upon in hard times. The RFS mapping encompasses 120,000 ha of rainforests, while not all this will have burnt, as shown by Terania Creek a lot has.

The big old trees are irreplaceable, the eucalypts may live for 300-500 years, or more, and the Brush Box at Terania Creek have been aged at over 1,340 years old. The older they get the more essential nesting/denning hollows, nectar, browse and other resources they provide for a multitude of species.

Most old trees have been lost through clearing, ringbarking and logging. Now the death of the survivors is being hastened by drought, and in huge numbers as successive fires eat away at their bases. They are also routinely cut down and bulldozed to control fires.

Over half our remnant old growth forest has been burnt this year. Hundreds of thousands of the oldest remaining trees have perished. Their loss is tragic.

Dailan Pugh
November, 2019