On the flight back from the Bungle Bungles we circled over the worlds largest diamond producer, the Argyle Diamond Mine. Each year this mine churns out over six tonnes of diamonds. The majority are of 'industrial' or 'near gem' quality, but 5% are of the finest in the world, including famous Argyle pink diamonds which have sold for $1M per carat (0.2 gram).
Until recently the mine was all 'open cut' but they have decided they can extend the mine's life until 2020 if they continue underground.
I'm not so sure. It's shaped like a human head and shoulders. An angry Aboriginal spirit perhaps, disturbed by the mine?
Here we were above the pit, looking directly down. There's a water truck
damping down the road - see how the road
colour darkens when wet? Behind it is a yellow grader and behind that
is one of six dumpers visible in the photo.
Check the activity on the left, it's enlarged in the image below.
There is dozer pushing dirt down a slope for the shovel to pick up and
load onto a dumper. A second dumper
is waiting to load. On the right is a white ute facing out of the picture.
Compare its size to the dumper's tyre.
Given the size of the lake, the dam looked quite insignificant.
Another view over Lake Argyle, the water reflecting the deep blue of the sky.
A few days later we took another excellent
tour, this time being driven out to Lake Argyle in a small bus. There
we boarded a boat, the captain of which was our versatile bus driver.
We spent two and a half hours cruising among islands and learning more
about the dam project, the lake and many fascinating statistics. One thing
I've noticed is that statistics tend to vary slightly according to who's
telling the story, so it may be that some I repeat here are not 100% accurate.
Try these:-
• During the 2000/2001 wet season, the water level in the lake rose to 7 metres above the level of the spillway. One million litres of water cascaded over the spillway every second. In one and a half days, enough water had overflowed to supply all of Australia for a year. Where did it go? Out to sea.
• There is sufficient storage in Lake Argyle to supply every person on earth with two tonnes of water. Residents of Manchester, you get yours as rain every Sunday afternoon.
• Only 10% of the water leaving Lake Argyle is used for irrigation, the remainder flows to the sea.
• The annual rainfall in the Lake Argyle catchment area is actually less than that which falls on Perth.
• A New South Wales farmer paid $1,000 for a megalitre (million litres) of water including licence fees, pumping costs, etc. A Kununurra farmer paid $2.49 for a megalitre. Moral of this story: Leave the Murray, come to the Ord.
This comparatively small dam (pictured below) has a core of impermeable clay supported by a 'filter' of small rocks which are protected by a layer of larger rocks. Concrete was used to secure the dams foundation to the bedrock and to seal fissures in the rock, but no concrete was used in the dam wall.
Our tour guide said that Lake Argyle water looked blue - until it was released back into the Ord River where it appeared green. He was right, it can be seen this picture. The explanation? The lake water reflects the sky, the river water reflects the surrounding foliage. Just out of sight on this side of the river is the hydro-electric power station which is pictured below.
Once construction began and the dam wall began to rise,
so too did the water in the lake-to-be. It took three years to complete
the dam as work had to cease during the wet season. Additionally the completed
work had to be protected against the terrific power of the water that
would flow over the embryo dam once the rain came. And after the rain,
when the water subsided, that protection had to be removed before work
could re-commence.
During construction, many islands were formed where higher ground was
surrounded by the rising water. On these islands wildlife became stranded,
eventually to drown or starve if nothing was done. A rescue operation
was mounted, television personality Harry Butler being significant in
his efforts to capture the stranded animals and release them back to safely.
The completed dam is not designed to withstand an overflow, so in addition
to the spillway there are several 'emergency overflow' locations where
water will escape before the lake level can rise to the top of the dam
in an exceptionally heavy wet season.
This small hydro-electric generator supplies
all of the power to Kununurra and Wyndham plus a good
percentage of the Argyle Mine's requirement. And in so doing, it doesn't
burn a gram of coal or diesel.
Taken from the boat on the 55 km. cruise from the dam to the town. Before the dam, this beautiful river would be a raging torrent for three months then dry up into scattered pools for the rest of the year. Now its flow is constant all year round.
The
cruise down the river - which becomes the "Lower Ord" below
the dam - was just beautiful. Our captain for this part of the tour, Shaun,
was one of those people who know every plant and animal, including their
Latin names. He was a mine of information and able to show us a myriad
of things we'd never otherwise have noticed. His eyesight was also remarkable;
he spotted a recently hatched crocodile basking on the mud beside the
river. Did I mention that there are an estimated 7,000 freshwater crocs
in this section of the river? Yes, I did, on the last page.
Fruit bats at rest.
In one of the creeks we went up, Shaun showed us a colony of fruit bats
hanging in the trees. These bats will never land on the ground, he told
us, because they can't take off again. If, by some circumstance, they
do find themselves on the ground they will immediately claw their way
up the nearest tree to a height from which they can drop, open their wings
and fly.
Lower down the river, soon after the sun had set, we witnessed thousands
upon thousands of these bats setting off for their nightly meal.
The picture depicts but a fraction of the stream of fruit bats (a.k.a. flying foxes due to their fox-like faces). Look to left or right and the stream continued. Wait for a minute then look again - still they'd be coming. Bats are the only mammals able to fly and a female only has one young at a time. When she flies it clings to her chest fur where she has a nipple to feed it.
