waterrightseeker, I wish you had defined the term 'water rights'. But here goes.
Conflict over water rights go back to biblical times. (Genesis 26: 12 to 19. And NO! I did not live in those times).
Water appears to be free like the air we breathe but it is not, because it is so scarce. (I think that less than one percent of the water on the planet is available for agricultural and household uses). This scarcity gives rise to conflict over who has the "right". Recently Georgia sought to establish "its" right to limit the outflow of "its" water resources. There are numerous examples world wide.
I do not believe in "water rights" in the context of "Constitutionally Guaranteed Rights". I think of water in terms of "priorities" and for every priority rating would come a commensurate responsibility for water conservation.
The highest priority would go to Agriculture and Household uses. Within this, commercial agriculture would get priority over ornamental agriculture (horticulture) and water for drinking would get priority over water for washing. The farmer and gardener would be required to prevent runoff and households, to utilize "grey water". And all this to be consistent with good public health. Increasing human life span can be directly correlated to the how far along a community has come in developing two separate systems of potable water and waste water. Sometimes I fear that some water conservation practices can breach this 'separateness' and result in serious, even tragic, human suffering.
Finally, I feel very sure that science will come up with ways of speeding up the hydrological cycle. Nonetheless, I remember a quote from the 1990's ....the good news is that by the turn of the century, reclaimed water will be safe to drink; the bad news is that there still will not be enough to go around... (Exact words and source forgotten).