Like most western states, Oregon follows the “prior appropriation” doctrine of water use, often referred to as “first in time, first in right.” This means that when there is insufficient water to satisfy all water rights, water users with senior priority dates make a “call” to receive water, and users with junior water rights are shut off until the rights of the senior users making the call are satisfied.

Prior to distributing water from junior users to senior users, the Department’s watermaster staff make field measurements to validate the call and determine whether there is adequate water at the senior right’s point of diversion to satisfy the senior user’s water right demand. Once the calls are validated, the Department must begin distributing water from junior (newer) water right diversions to benefit the senior users.

The Klamath Tribes hold determined water right claims with a priority date of time immemorial, making them the most senior water right holders in the Upper Klamath Basin. The determined claims allow the Tribes to provide for a healthy riparian habitat among other instream needs. The Department’s web page provides the latest information on the Klamath Tribes’ instream determined claims, displaying a graph for the water year and showing the current mean daily streamflow along with past streamflow measurements made by Department staff.

Water distribution notification occurs by postal mailing of a notice of regulation, which requires junior water users to shut off their diversions, pumps, or wells. Water management through regulation and distribution occurs across much of Oregon every year, and has for a century. Watermaster staff follow up with field checks to individual points of diversion to ensure that water use is in compliance with regulation orders.