If I mix my time and labor with raw material to produce something, I have a right to my production; it is a property right. Property rights begin with self-ownership of life, body, and mind.
Yes, ownership of land is a property right. Property rights are natural rights. This is what I was referring to when I said first use. If you are first to use a natural resource (mixing your labor with the raw), you have ownership of that part of the resource, including water.
This might help explain better:
https://mises.org/library/who-owns-water