Nevada Water Law
Priority dates affect the allocation of water
Let's pretend our groundwater basin is a large bucket that contains 10 gallons of water. Two people want to use the water and each has a water right:

• Party A has a right to eight gallons of water with a priority date of 1925.

• Party B has a right to six gallons of water with a priority date of 1950.

Under the prior appropriation system, Party A has the right to withdraw its eight gallons of water first, leaving whatever is left to Party B because Party A's right has an earlier priority date.

Party A maintains its priority to the eight gallons unless it fails to use the water for five consecutive years. If the water withdrawals cause impacts on the other water right holder, the younger right (also known as a junior right) can be reduced or canceled.

Consequently, priority dates are very important for all water rights. Under Nevada water law, if a party fails to use all or a portion of its water for five consecutive years, the Office of the State Engineer may require forfeiture of the underlying right to the water.