Wot? Digging a channel to let the sea into Lake Eyre, yet again?
There are two aspects of it that should not be in dispute:
First, the digging job would keep a number of excavators in work for a while.
Second, the removal of evaporated salt accumulating in the new water-hole each year would also provide a lot of work.
Before anyone starts sharpening up their shovels, I would imagine they would have enough interest to do some simple mathematics in relation to the task(adding, multiplying and dividing is the limit of skill needed).
Should such interest be there, then the task is to assess the size of the channel needed, and also the amount of annual salt removal.
Data covering the following would provide a sufficient base for the calculations.

The area of the proposed lake; annual evaporation rate in that region; the percentage of salt in seawater; the slope between the sea and the surface of the new pond; the rate of flow needed through the style of channel chosen; the rate of flow possible for the water in the channel.
The maths would lead to the same result, whether it be a variety of green or red; left or right.