A more thorough explanation:

Prior appropriation doctrine

The prior appropriation doctrine is a rule that determines water rights based on the priority of beneficial use. This means that the first person to use or divert water for a beneficial purpose can acquire individual rights to the water.

For example, if a farmer diverts water from a river to irrigate their crops, they may acquire the right to continue using that water for irrigation. If another person downstream wants to use the same water for a different purpose, such as drinking water, they may not be able to do so if the farmer's prior use takes priority.

Another example could be a mining company that diverts water from a stream to use in their operations. If a recreational fisherman downstream wants to use the same water for fishing, they may not be able to do so if the mining company's prior use takes priority.

The prior appropriation doctrine is based on the idea that the first person to use water for a beneficial purpose has a right to continue using that water. This means that if there is a limited amount of water available, those who have acquired rights to the water through prior appropriation have priority over those who have not. The examples illustrate how this doctrine can affect different users of water and how it can be used to allocate water rights.