Do they have eminent domain? Are they forcing people to sell with a gun to their head? Could anyone else have filed on the “unappropriated groundwater”?
They’re powerful enough (thanks to Sen. Harry Reid’s son being on their board) that they can warp the law to their ends.
When they needed more money, they created an act that allowed the BLM to sell off public lands to developers and then divert 50% of the proceeds to an account to buy “sensitive lands” (which are always private lands with water they want - species or habitat considerations never enter into it). They just jack up the price as high as they need to buy out the pivotal ranch or farm in the area.
Unappropriated groundwater: Yes and no. Private users could have filed on it, but the politicians and environmentalists have blocked the Desert Land Entry conversion of public lands to private lands to make beneficial use of the water - so private use of the water is restricted. So the water remains unappropriated until the SNWA comes along.
But then the SNWA, being very politically powerful, has changed the state law to allow them to file on unappropriated water, then not use it (which would be required of anyone else filing on the water). The SNWA then simply pays a fee and updates their filing - for years and years (in some cases, nearly two decades), even if they don’t develop the water rights. Anyone else has five years to use it or lose it.
Long story short: Harry Reid (and his clan), coupled with California land developers who have moved into Nevada, have used the power of the federal government to take water from entire counties.
If you’ve ever farmed or ranched (and it is abundantly clear you never have), you’d also know that municipal water use gets a use preference over ag water use, which circumvents the “first in use, first in right” law of water. So the cities can buy up a junior water right, convert it to municipal use, and force other water rights holders to sell because when the cities over-appropriate the water in a basin/river/etc. They have a “more important use” and deep pockets to allow them to force forfeiture on more senior water rights holders.
Suffice to say, the free market bromides of “let the highest bidder win” are long-term economic disasters for both the private sector who has existing property rights and the taxpayers who have to clean up the mess decades after the fact. The “let the highest bidder win” is nothing but simplistic shorthand for “let the taxpayers of tomorrow put money in the pockets of real estate developers today.”