There are several types of water rights:
1)Riparian Rights - Usually requires ownership of land next to a water source (river/lake) see end note *
2)Prior appropriation rights - Water rights granted to first to request said rights historically for a beneficial purpose (You might be competing from someone who can trace it back to the first settler family in the area in drought years). You cannot store for "dry" years in most states and loose the right if not used. You may also not draw more than is specified and/or nessisary. Most of the western states follow some variation of this rule. Some states allow you to "take" more than allocated water if you return the same amount in some form (that's not waste water)
3) Groundwater Rights - Use of water underneath the surface that allows you to drill a well. Usually hard to "lose" vs riperian
4) Water catchment - Law currently developing, basically catching rain/snowfall into a cistern and storing it.
5) Moving between aquifers and watersheds is generally hard if not impossible out west (IDK about the east)
6) You can sell the right (like a car), lease it, or contract an obligation to provide a pre-specified amount per year
7) Some states you may loose water rights not using them, this is most common with riperian rights, does apply to groundwater sometimes
8 ) CA does some unicorn "community allocation of water" bs as a holdover of Spanish law I don't fully understsand.
It must be noted that depending on state law, riparian, groundwater and catchment may or may range from extremely hard to get to meh and may also have prior appropriation apply.
By region:
Western states:
Rainwater/snowfall collection is illegal generally due to the demands of the Colorado river treaties (esp if you divert). Land and water rights are usually separate and you will be sued into oblivion if you piss of the locals enough because water usage is a big issue. Riparian rights are easier to get than groundwater but usually cannot be diverted.
Cour 'd Alene river watershed has a lot of pollution. If you can get somehow unpolluted water it's a premium due to mining issues. Same with Butte's Clark Fork due to mining.
Texas :
Due to it's size and varied geography is unique riparian rights are heavily restricted, groundwater rights laws are pretty loose (If you own the land you have a right to drill for personal use) may not be diverted without state/EPA approval in some areas (west of I-35 particularly). They really don't give a fuck in the east closer to Lousiana since too much water compared to say, El Paso. Some areas have pump limits for groundwater and must be metered.
Plains states:
Mostly groundwater rights, there's a bunch of fighting over whose responsible for the draining the Ogallala aquifer in the region (Hint: All of the states). There are pump limits in most of the areas. Ogallala doesn't recharge well so if it's gone it's gone.
Eastern Seaboard:
Riperian rights may be easier to get than groundwater. Groundwater comes with the land sale usually. TVA is the biggest headache out there. I think collection is ok / don't care as long as its not too massive.
Florida is an outlier due to EPA and wildlife preserve shenanigans I don't understand.
By type:
- Riperian is useless if you don't use it yearly in most of the mountain west (probably the east too). Also a complete clusterfuck if it's the Colorado or Rio grande watersheds Columbia river is easier since leafland is upstream.
- Groundwater okay but groundwater reform is an issue and may fuck you if they pull an AZ and change groundwater to riperian-lite
- If you bet on a city it'll be a long term bet unless you can score a big deal like the area east of Austin
- If you divert enough to a city farmers and locals will probably fuck with you (See: California Water Wars)
- Selling water to farmers will depend on climate, year, and your senority of right and volume avalible.
- Adverse possestion of ground water rights is theroetically possible, but not settled law if someone slant drills you (has never been tested in court)
- Try not to piss off your neighboors if you buy rights in the Great Basin region. You're gonna be pissing people off by just buying so keep enemies to a minimum
*In riperian rights, upstream shall not abridge down stream, and if your watershed crosses international borders downstream of you it is a clusterfuck. The feds must guarantee an amount of water to the other nation, and the states must guaranteee an amount to the feds, etc etc.