Imagine the desire to divert an entire river
What must motivate people to do that? what would make that worthwhile.
Gold my friends, gold is what motivates people.
At least that was the case in the 1870's in Hepburn springs in Victoria, Australia. If you know a little history you know this was around about the 'Gold Rush' in Victoria when there was gold in those these hills. (or rivers or whatnot)
People were flooding in from all over the world - if I've done my maths right they were pulling out about $3.6 billions worth of gold every year in today's money in Victoria around then, so if you thought there was gold under the river, and if Gold Rush has taught me anything (other than with the excavator dies you go to an ad break) it's the gold lives in lazy bends of rivers.
So I guess the that's the case what you do is you dig a big hole through the rock for the water to go through allowing the rest of the river bed to dry up and then wander in a pick up the gold - simples.
It's now a series of walking trails where you head down to the blowhole, which is hard to see but at the top of the second photo, were we then at the very start of Autumn so the river was pretty low, but here is a picture from one assumes winter from the national parks website:
The walking trails follow the route of the now dried up river, the first photo is looking the other way here the new diverted creek goes and you realise that this idea gave them access to a lot of good ground, I can really fathom how they managed to bore through the tunnel - it's not huge - maybe a metre high and wide and maybe 25 metres long, but in 1870 with so picks this would have been fairly difficult one assumes.
But it does make for a nice morning walk nowadays.
great photograph