About Me

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I've been a Canberran since moving here from Adelaide on the first day of 1980. I now live in suburban Duffy with my partner Louise Maher, ABC 666 radio and on-line journalist. Among my early memories is following Sleepy Lizards (Shinglebacks) around the paddocks north of Adelaide, guarded by the faithful bull terrier. I have always been passionate about the natural world, trying to understand how it works, how the nature of Australia came to be, and sharing those understandings. My especial passions are birds, orchids and mammals. For much of my life I have been a full-time naturalist, running bush tours, writing books etc, doing consultancies, presenting a regular radio slot on local ABC, chairing a government environment advisory committee and running adult education classes. Recently I have eased back somewhat, but am still writing, teaching, doing some radio work and running overseas tours - as part of my fascination with our Gondwanan origins I've been running tours to South America for the past decade. I was awarded the Australian Plants Society Award in 2001 and the Australian Natural History Medallion in 2006, both for services to education and conservation.

Monday, 21 July 2014

As You Lake It

Having a couple of other matters demanding attention at the moment (ones more related to earning a living than is writing a blog post!), I thought to take the easy way out and just offer you some hopefully attractive pictures of some lakes. Inevitably I soon starting thinking more about lakes, and what they are, so my offering has become a bit more than just a series of images, and hopefully is more interesting for that.

A lake is of course a body of water, though there is no consensus as to just how big (ie how large it has to be to graduate from being a mere pond or pool); different suggestions range from a couple of hectares to 40 hectares. It can't be connected to the sea (so is usually, but not necessarily, fresh water), and is land-locked except for an inflow and outflow channel, though these are optional. However, there are several kinds of lake, based on origins and flow characteristics.

While less obvious in Australia (where we tend to be a bit light on with regard to water anyway), lakes originating with glacial activity, past or ongoing, form a substantial portion of the world's lakes, so let's start there. Glaciers can gouge out hollows which later fill with water, or dam valleys with moraine material left behind as melting glaciers retreat.
Dove Lake and Cradle Mountain, Tasmania.
Tasmania underwent major glaciation during the last glacial period, far more than did the mainland.
Lake Cootapatamba, Kosciuszko National Park, New South Wales.
These southern alps also had minor glaciation until 10,000 years ago, and Cootapatamba
derives from that. It is Australia's highest lake.
El Cajas National Park, in the high Andes above Cuenca, central Ecuador, is studded with glacial lakes,
above and below. The altitude here is over 4000 metres above sea level.

Further south, glaciers are still very much a part of the Andean landscape, and glacial lakes abound.
Lago Todos de los Santos near the Argentinian border with Chile,
east of Puerto Varas.

Lake in the high pampas, Andes east of Coyaique, Chilean northern Patagonia.
Further south still, the mighty peaks of Torres del Paine National Park in far southern Chile are not part of the Andean chain, but are actively glacial and at their feet are some superb lakes.
Lago Nordenskjold, Torres del Paine National Park.
In front of the towers (above) and with wind ripping the surface from the water (below).


In Australia, in the arid inland, many lake are endorheic - that is the flow is only into the them, and they are dry much more often than not, though they are based on vast ancient rich lake systems, with flamingoes, fresh water dolphins and crocodiles not so long ago. Mostly they are salty, because of ongoing evaporation.
Lake Amadeus, near Uluru, central Australia.
Part of a vast 'fossil' lake system, 500km long and covering 1750 square kilometres.
Lake Gilles, South Australia, in its normal state (above)
and as much more rarely seen (below, in September 2013).
Waterholes, often called oxbows, or billabongs in Australia, form when a river changes course - as often happens during floods especially - and the old bed is cut off from the main stream and fills during times of overflow from the new bed. In arid Australia such waterholes can also form in the main bed which very rarely flows, but deep holes retain water for considerable time; they are critically important to life in desert landscapes, and can have their own endemic fish and invertebrate species.
Combo Waterhole near Winton, north-western Queensland.
(It was here that the great Australian bush poet and journalist A.B. ('Banjo') Paterson was inspired
to write Waltzing Matilda, sometimes thought of Australia's 'other national anthem'.)
Cocha Salvador, Manu National Park, Amazonian Peru, at dawn.
A large oxbow lake.
Volcanic craters can fill with water to form sometimes large lakes.
Crater Lake near Kibale, Uganda.
Larger crater lake, Queen Elizabeth National Park, Uganda.
And while in that part of the world, many of the great east African lakes are formed on the great rift which is splitting Africa. Such lakes are unusual in that they are getting deeper faster than siltation can fill them up.
Lake Edward, Queen Elizabeth NP, Uganda (above)
and Lake Victoria, Entebbe, Uganda (below).
Two mighty rift lakes.

Fresh-water lakes can form in the dips behind sea dunes.
Meroo Lake, south coast New South Wales.
And unlikely as it seems, sand can support lakes well above sea level, though it is unusual. Some famous examples, 40 or so of them, are on Fraser Island, off the southern Queensland coast.
Lake Mackenzie, Fraser Island, a perched lake on sand.
So, a brief review of some lakes I have known... I hope you enjoyed the journey too.

PS I've just realised that this is the first posting ever by me without a named plant or animal, so I should rectify that.
Chilean Flamingoes in glacial lake in front of the Towers, Torres del Paine NP.

BACK ON THURSDAY


2 comments:

Flabmeister said...

My memory from school days - yes, in this interglacial epoch - is that oxbows tend to form as cut off meanders. Thus they are a product of flows in flatter areas. Around Louth NSW the Darling drops 14mm per kilometre and is thus prime oxbow territory.

Martin

Ian Fraser said...

Absolutely! Likewise SW Queensland, the Lake Eyre Basin in general, and indeed all the lower Murray.