The weirs not far up the channel restrict the amount of flow inland/up the river. The mouth of the river isn't much smaller than it used to be, but you can see where it is silting up on aerial photographs. Think of how much the tide wants to flow in and out of the river, then restrict how far it can flow and there is the problem. I'm yet to see an assessment or comparison between Murray and overseas rivers of how much outflow of freshwater to the sea there is or ever was. And that includes when I was in that field, years ago. Take a well know river, eg the Amazon and you can observe that it flows fresh, turgid but fresh, water out into the sea for many km due to the force of the water behind pushing whats at the front along. Same with Chinese and to some extend European rivers. Doesn't happen so much here. As I said with our mountains our river systems aren't conventional. How many places globally have an entirely inwards flowing river system like the Lake Eyre basin?
