The river, locks, weirs

A few people have asked me "why locks on a river?". For the benefit of anyone reading this blog from outside Australia, I will attempt to explain. Any river nerds can please excuse small inaccuracies, as I believe the basic explanation here is correct.

You probably think a river is something with water in it. This is mostly not true here in inland Australia. Very few (any?) of them flow naturally all the time. Even the Murray has run dry. It starts in the Snowies and runs through 2400 kms of what is (or was) basically desert or near desert. Sturt just got lucky when he first went down the Murrumbidgee and the Murray.

We stopped a week or so back at Border Cliffs, which is the first civilisation/supplies (you do pass locks on the way down) after Wentworth and is 188 kms down the river from it. Situated there is the old customs house which, pre federation, the SA government set up to tax river traffic, which was extensive at the time. However, just a little later, the great drought struck and the river dried up completely. After 2 years, they abandoned the customs post and attempt at duties collection and it was never reinstated due federation. The constitution says no restrictions on trade between the states.

The Darling has supported paddle steamer traffic, and a couple of them are still to be found high and dry and miles from the river, where they ended up in flood times. So that is the other feature of the rivers. Feast or famine. Droughts and flooding rains, in the words of Dorothea Mackellar ( http://www.dorotheamackellar.com.au/archive/mycountry.htm ) The Paroo, when it flows, runs out of Queensland and wanders around before ending in a swamp most times. But in a huge wet, it gets to the Darling. The Lachlan fades into a swamp after staggering about over half of NSW, and did so even in the time of Sturt because his progress on land was blocked by the towering reeds in the dried up swamp where it might enter the Murrumbidgee in a big wet, so he put their boat in the water and went down the Murrumbidgee that way.

So keeping the Murray wet is a big deal, for irrigators all along the river and to guarantee a water supply to South Australia. The weirs, and a lot of careful attention to storage levels and flows, do this job. The locks permit boats to pass the weirs. There are also fish ladders.

If you are flying over inland Australia and see rivers on your chart, look for lines of trees (in contrast to scrubby stuff and red dirt) rather than actual water. In times of flood, look for lines of trees sticking up out of a great expanse of muddy water.