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Christmas Bells - Blandfordia nobilis

Wednesday, December 24, 2008

Nepean River - Absolute headwaters.

On Sunday afternoon I went with some other friends to visit Emma and Jonnie and their family for Christmas celebrations.

I had known for a long time that one of these little gullies (which head off towards Sydney, from the northern edge of the Robertson district) was the actual head of the Nepean, but apparently this is it.

The light was suitable, in the late afternoon for photographing the local valley, which I had ascertained from some other friends, was indeed the head of the Nepean River. Emma confirmed it for me.

Looking westward, and uphill, you can see the boundary of this catchment. Just over this hilltop, in the westerly direction, one comes to Robertson proper, and the headwaters of Caalang Creek, the start of the Wingecarribee River system- which runs to the Wollondilly River and hence to Warragamba Dam. So, over the hill lies a different catchment.
Click on these images to enlarge them
(to make reading the labels easier).You can see where there is a very small farm dam, which I have marked (above) and the line of a soak which leads down to the first properly formed creek line - the true start of the Nepean River valley.This lovely scene shows the real start of the Nepean River - as a recognisable creek.And to put it all into the picture, this image shows the start of the Kangaloon forested area which is the start of the Sydney Catchment "Special Area". In the far distance is the Kangaloon Aquifer area, and the main part of the "Catchment".
Once the Nepean River crosses "Tourist Road" (about 3 kilometres below this point) it enters the true "Catchment" it becomes a classic river on a sandstone rock base (having started up here in the basalt "red soil" country). Once within the sandstone area, it quickly starts to form a series of canyons and gorges.

The Nepean River merges with the Hawkesbury River, at the base of the Blue Mountains. The Hawkesbury-Nepean River system defines the "Sydney Basin". This giant river then enters the ocean at Broken Bay, north of Lion Island, just north of Palm Beach (north from Sydney).

The Hawkesbury is the major river which one crosses on the way north to Newcastle. Gosford is located on the northen side of the River, as it enters "Broken Bay".

Very few people, (especially few Sydneysiders) realise that the mighty Hakesbury-Nepean River system starts right here, on the edge of Robertson. Silly them!


mick said...

That is very interesting. The labeled photos make it very clear. When I think of the many times I have crossed the Hawkesbury River on the Pacific Hwy and then on the motorway it makes it even more interesting to see the headwaters of the river system.

Denis Wilson said...

Ah, good. At least you do know where it ends.
From a tiny stream, just a "soak" right to the massive river on the other end, which carved that huge valley, now you have seen both ends of it!

Duncan said...

Interesting post Denis, all the best, D.

Jarrett said...

Now I don't want to seem to existential, but to call some particular spot the headwaters of the Nepean ... what does that mean, really?

Isn't any point on any edge of a watershed a headwater? Are you simply saying that because the river all the way to this point is called the Nepean, as opposed to other tributaries, that this headwater is special?

OK, but does the continuity of the name of the river indicate some objective geographical fact, or is just a human convention? For example, when two rivers meet, is it always the larger one that keeps its name, while the other is a mere tributary? It's certainly not the most distant headwater of the Nepean system, as the Wollondilly seems to extend out beyond Goulburn.

Just wondering ... Happy holidays!

Denis Wilson said...

Hi Jarrett

You are being a bit existential, but some people do that at Christmas time. Indeed it is a bad day for all sorts of things. I figure that questioning the precise meaning of my terminology is not too much for me to worry about, really.

Certainly, you are correct that the Wollondilly does extend much further south. But it is its own separate river. It is a major tributary of the Nepean, but not the major tributary. The Cox's River, which starts way around the back of the Blue Mountains, near Lithgow (the Blue Mountains are NOT a divide, despite being far higher than the country between Lithgow and Bathurst, which is where the divide actually occurs.) The Cox's River might even be longer, but certainly it carries more water, normally.

Technically, it could be that what I referred to a s a "divide" is a "sub-divide", as the Caalang Creek (over the hill in my photo) and Wingecarribee River- which Caalang Creek becomes - are both, tributaries of the Wollondilly, which does eventually flow into Warragamba Dam (where it merges with the Cox's River). Together they both flow back into the Nepean, which subsequently eventually becomes the Hawkesbury (after the Grose River enters the system).

But the Nepean has the name, and yes, this is the very furthest extent of the various creeks which form the Nepean. So, I do not have any problem with calling it the absolute headwaters of the Nepean. The SCA regard the Nepean Catchment as its own "Catchment", and it is managed as a separate unit, and is preserved mostly as "natural bushland". The Wollondilly catchment is mostly degraded farmland.

Cheers and I hope you have a happy and prosperous New Year.