Curtailing water use
A person or group may be granted a water right to use a volume of water, for a defined purpose, in a specific place. Under Washington’s “first-in-time, first in right” legal framework, a person who established a water right first has a senior water right. This gives them the right to withdraw all their allocated water before the next person in line, who holds a right “junior” to their senior right.
The water use of junior water right holders can be interrupted if they are impairing the water use of senior water right holders, or there is a risk of impairment because a water source is insufficient to meet all the water demands on it. In some of the state’s watersheds, a minimum flow level has been established in regulation for that stream, known often as “instream flow.” Based on the date of that regulation, water right holders with priority dates “junior” to the instream flow rule can be curtailed if the flows in the stream are below the flow levels set in regulation.