In assessing rights of streams, rivers, and lakes, what is the prior appropriation doctrine?

The prior appropriation doctrine is all about “first come, first served” when it comes to using water from streams, rivers, and lakes. Under this doctrine, individuals can acquire water rights by actually using the water for a beneficial purpose (like irrigation, drinking, or farming).

In other words, whoever uses the water first has the strongest claim to it. This means if you were the first person to start using water from a river to irrigate your crops, you have the top priority—no one else who comes later can take away your right to that water. It’s summed up as “first in time, first in right.”

Your rights are based on priority of beneficial use, meaning you can keep using the water as long as you're putting it to good use. But if you stop using it or waste it, you could lose your claim, and someone else might take your spot in line.

The prior appropriation doctrine is especially important in the drier western states where water is scarce, and it helps ensure that those who make productive use of the water get to keep using it, as long as they maintain their priority.