I frequently spend long periods in the AZ desert. This is a fragile ecosystem. In some places it has a concrete hard surface, but it is only a few inches thick. Water dumped on this surface will soften it and create a hole. The hole will remain for many many years. The seasonal rains will expand the hole. I suspect that the seasonal rains do not cause holes because the large amount of water immediatly runs off into the gullies (arroyos??) and usuall no pockets of water remain on the surface. Sounds odd, but that is what happens.

I have frequently been warned by various wardens, rangers, LEO's that to dump water is illegal as well as very damaging to the ecosystem.

Different places require different attitudes and protocols.