If 4 cents per 10 gallons is correct, it’s just 16.8 cents per barrel.
However, you also need to dispose of the salt and the toxins, store the clean water, and transport it to the crops.
In any event, how much are farmers willing to pay for irrigation, and is the top soil any good in that part of Texas?
I’d be surprised if the Free Republic folks on this thread were the first people in America to think about this, which probably means that irrigation in that area is not commercially viable.
It's viable, just not a lot of water.