The problem is that a lot of farms and ranches get their water from wells on the farms/ranches themselves. For those that have to pump in their water from elsewhere, then yeah, let's get water prices restructured. For those pumping their own water from their own property, however, we'd need some major rejiggering of property rights in order to justify charging land owners for the use of what's arguably their own property, and I'm not sure if that rejiggering would be a net good. I suppose a property depth could be enforced much in the same way that a property height is already enforced (in order to prevent landowners from restricting air traffic, for example), but that's going to have some huge backlash, I'd reckon, seeing as how much of an investment is required to build wells / water tanks, run power lines, etc. Perhaps mandatory metering of electric wells combined with water usage limits ("this is how much water we've detected to exist underneath your property; we'll charge if you use more than that, and credit if you use less than that") would be a good solution/compromise?