I agree why cant they grow it there.
Does the water have to flowing at all sorry I don't know much about rice having never seen any paddies..

Cotton is another one that waste so much water shame really but someone is getting rich and I am sure they are greasing the hand of the government that is in power to be able to do these things..MM.

Cotton is also there also corn and sunflowers and in huge acreages there is 25mil pipes coming out of the channels about a metre apart and they are currently harvesting and resowing rice paddies
the rice paddies remind you of a swamp always under water

I'm somewhat sympathetic to water usage for agricultural purposes. I buy and eat their products so I can't be too hypocritical. I imagine the wetland areas are most likely open to uncontrollable flooding during the wetter months and draining the areas for harvest would be impractical. Besides we've done enough damage destroying our ecosystems for the sake of agriculture without looking towards destroying our wetlands.

If you want a target to vent about inappropriate water usage, I'm certain of at least one major Victorian nursery that has the facilities to recycle its water but runs entirely off mains water because it's cheaper. I can't imagine they're alone. There are, of course, exemptions from water restrictions for the nursery industry but to me that reeks of the big guns making use of laws aimed to accommodate ma & pa nurseries so they can put profit ahead of social responsibility. Lets not even mention the Commonwealth Games village, where they were watering the lawned areas in the middle of 30oC days. Of course why would the government penalise a government sanctioned activity.

There are lots of cases of inappropriate water usage worthy of venting your disapproval that are far more distasteful than the perceived overuse of water by primary industry.