Back then there were all sorts of wonderful stories behind the changing water level

When Brad Pillans first moved to Canberra from Moruya as an 11-year-old in 1963, Lake Burley Griffin was empty and Lake George was full. It’s hard to imagine today, but for the better part of that decade, the now much-diminished Lake George was a watersports wonderland, complete with a yacht club, a speed boat club and waves in windy weather.

On summer weekends, the Pillans’ speedboat could be seen on Lake George, navigating around 10 or 20 others, with Brad’s mother trailing on waterskis while his father took photos and Brad and his two brothers and sister splashed along the beach. Pillans soon learned to water-ski as well.

“On a bright sunny day the lake was blue and wonderful,” recalls Pillans. “I couldn’t think of anything more enjoyable than Sunday afternoons, after church, taking the boat out to Lake George with a picnic lunch and playing in the water until it got too cold and we had to go home.”

But in the late 60s the family fun was disrupted as the water level began to drop dangerously low.

“We kept waterskiing right up until the fence lines started to show,” says Pillans. “I remember quite clearly a boat hitting a big rock one day and it just sank as I watched. That was the end of it.”

The boats have never returned and, apart from a half-hearted fill in the late 80s, the water component of Lake George has been largely nonexistent ever since.

Now a professor of geology in the Research School of Earth Sciences, part of the ANU College of Physical and Mathematical Sciences, Pillans is returning to the happy haunt of his youth to study the mysterious history of the ever-changing lake.

“I’m sort of realising my childhood dream of doing research on Lake George,” he says.

Pillans first planned to investigate the geological history of Lake George when he came to ANU as an undergraduate. Unfortunately, someone had pipped him to the post.

“It turned out a student called Ross Coventry, who was several years ahead of me at ANU, had recently done an in-depth study for his own PhD.

“Back then there were all sorts of wonderful stories behind the changing water level, involving subterranean tunnels going across the Tasman Sea, and as Lake George went down, a lake in New Zealand would fill.

“But the truth was really very simple: whether it’s filled or not is really dependent on the balance between local rainfall and evaporation.”

Pillans ended up doing fieldwork for his ANU PhD in New Zealand and took up a lectureship at Victoria University of Wellington in 1983. He returned to ANU in 1994 and has been here ever since, but this is the first time he has visited Lake George for scientific reasons. Over the next three years, he and a team of geologists and archaeologists will delve into the region’s history, recreating a detailed picture of the past environments in order to understand present and future
environmental changes.

“Lake George is a unique record and one of the longest more or less continuous archives of its kind in the world,” says Pillans.

“The layers of sediments in the floor of Lake George are 150 metres deep; that’s material that has been washed into the lake from the surrounding catchment and has built up slowly over several million years. And in those sediments are fossilised pollen grains, from which we can reconstruct what sort of vegetation was around and, in turn, what the climate must have been like.”

It’s not only over the last half century that the lake has transformed almost unrecognisably. In fact, Lake George’s history is full of surprises. Over the millennia, the landscape has undergone numerous and varied makeovers.

“We know that during very cold glacial periods, trees were almost absent; it was a sub-alpine grassland much like you’d see in the Snowy Mountains today. There were even times when it was much wetter than it is now and there were rainforest trees and ferns whose nearest living relatives grow, today, in places like New Zealand, Tasmania and New Guinea.

“And this amazing variability was driven by the major climate changes that affected the whole world, including the coming and going of the big ice sheets in the Northern Hemisphere during the last few ice ages.”

The water level has also undergone dramatic changes. Historical records suggest that Lake George was several metres deep when it was first seen by Europeans in the 1820s, and the beaches and shorelines indicate the waterline reached to 37 metres around 30,000 years ago.

Pillans has witnessed first-hand more recent changes in the local climate.

“There’s no doubt the climate around Canberra has changed a bit since the 60s,” he says. “As kids, when we got tired of playing in the lake we’d scamper up the very steep scarp right next to the highway to admire the view and one time we found snow on the top!

“On another occasion, in July 1965, there was an extraordinary storm that came up from the south and just blanketed the whole south and east of Australia. Canberra was covered in six inches of snow which stayed on the ground for a couple of days. In a way, it was like a little window into what it would have been like 20,000 years ago when it was a lot colder.”

Pillans, who has been involved in paleoclimate research for most of his career and has studied records of past environmental change all over the world, says there is no doubt that the humaninduced rise in atmospheric carbon dioxide is affecting the climate. He says Lake George harbours invaluable clues as to what a high-carbon dioxide environment might look like.

“We know from records in Antarctica [where Pillans spent a field season in 1984] that global atmospheric carbon dioxide levels haven’t been as high as they are now for more than a million years. So in a way we’re in uncharted territory.

We need to look a couple of million years back and there are certainly sedimentary layers at Lake George that date back to a time when atmospheric carbon dioxide levels were probably as high as they are now.

“So from this wonderful geological record we’re going to interpret what Lake George was like back then, in terms of vegetation, water levels, rain fall – the whole environmental package – because if we can understand what was happening then, we can understand better what might happen in the future.”

It’s not only the changing climate that has altered the landscape. The team will also be looking at the human history of Lake George, both in recent times and ancient.

“We’re very interested in evidence for Aboriginal occupation in the area. It would have been a very attractive place to live when the lake was full of water and fish,” says Pillans.

“We know already from past archaeological work that Lake George was visited by Aboriginal people but we want to find out how long ago they first came to the area and also how they utilised the landscape.

“It’s well known that Aboriginal people used fire to manage the landscape in their hunting and also as a way of promoting the growth of plants that they used as food at certain times of the year. And what’s the evidence of burning? Charcoal. If we find high amounts of charcoal in the sediment, that’s strong evidence for fire and when charcoal levels dramatically increase then usually it’s interpreted as a human impact.

“We’ll be looking out for artefacts as well – a range of stone tools, and maybe some wooden ones too, if we’re lucky.”

More recent evidence of human habitation is easier to find.

“I don’t mind the wind turbines [installed on the east side of the lake a few years ago]. I find them quite interesting actually,” says Pillans. “I’ve always been a supporter of alternative energy sources and I see the turbines as an addition to an already stunning landscape rather than spoiling it. I also really liked the zebra sculptures that were in residence for a short time in 2010.”

Over the years, Lake George has been many things to many people. So which of its various reincarnations will Pillans remember it by?

“I’ll always look back fondly on my early days at the lake. To me it will always mean happy family outings on a Sunday afternoon in summer.

“And there’s no reason to suppose that the lake won’t, sometime in the future, return to how it was back then. It really depends on a run of above-average rainfall years and we’ve had three in a row now.”

Who knows, maybe Pillans will get a chance to waterski on Lake George one more time.