If you are considering buying a substantial piece of property for various purposes, you should understand some basic things about water use since your needs and the rights of others could come into conflict. The two main sources of water are below the ground and above ground. There are various laws and principles used in settling disputes that arise over both sources.
Underground Water Sources
An underground reservoir is called an aquifer, and water that permeates through rock, sand, or earth is called percolating water. Whether you use a well or collect water from a spring, if you use a large amount from an underground source on a regular basis, you could impinge on the water rights of other landowners and even cause changes in their land surface.
If the underground source is a stream, your state may use riparian rules. This means that you are allowed normal use of water in the area where it comes from, but there may be restrictions on its use in other parts of your land such as for irrigation of crops. If your locality uses the Common Law rule, then as long as you don't waste water or use it in a malicious manner, you can take as much as you want for your own use.
A lot of states use the reasonable use rule (or American rule) which is a combination of riparian rules and the common law rule. They distinguish whether the water will be transported to another site or used directly from the source.
When using it onsite, you can use as much of the water as you need but you can't maliciously waste it. On the other hand, if you transport the water to another part of your and or elsewhere, you could be held liable if your use impinges on the rights of other landowners who have land above the aquifer.
Your local court may use the Restatement rule or Restatement (second) of Torts § 858, and this means as long as your water use is reasonable, you would be free from liability.
Some states use a prior appropriation strategy which means if you were there first, you have more rights to the water than someone who buys property over the aquifer later.
If your area is experiencing a water shortage, the court may intervene and establish a plan called correlative rights to allocate water use fairly between each landowner. This could result in a restriction on transporting water elsewhere.
Above-Ground Water Sources
Land that is next to a lake or a stream is called riparian land and rights to the water are called riparian rights and again, your direct usage is fine, but there could be restrictions on irrigation, and also on the industrial use of it. You may have to apply for a water permit in the area you live for uses other than domestic and your usage may be determined either by prior appropriation, water flow, and reasonable use.
In many western states, usage rights could be dictated primarily by prior appropriation and beneficial use of water. However, some areas also consider the water flow rule, and under this your use may be restricted from altering the flow of the water because of the effect it could have on the flow of water through others' property.
Under the reasonable use rule, courts consider various factors when determining rights and liability. Community concerns could take precedence over your planned usage, which means that if an owner or entity is providing economic benefits to the area, their rights could supersede yours. Domestic use is considered next, and irrigation would be considered after that.
The best source of legal advice and state/local laws is a real estate attorney (such as one from Souders Law Group). If you are planning a substantial change or expect to make significant use of a water source, you will need to consult one to make sure your plans won't cause conflict with your neighbors or the community.