If Utah has a right to water from Lake Powell, it should take it. With Utah's growing population and ever-oscillating climate, obtaining and conserving water become increasingly more important.
I suspect one of the largest consumers of water in Kane and Washington counties is the LDS Church with its dozens and possibly a hundred or more buildings including ward houses, seminaries, tabernacles and of course the St. George Temple.
All these buildings sit on nicely landscaped, water-guzzling parcels. I would hope that they do not water in southern Utah like they do in Utah County: at the worst possible hours, for too long, too often, and when not needed.