What is the test for a common law right to water from the Kern River?

The parties use water from the Kern River pursuant to rights originally established in the late 19th century. As with all water rights in California, exercise of the right is conditioned on reasonable use of the water for a beneficial purpose. (See Cal. Const, art. X, 2.) In other words, the owner of the right to a quantity of water or to the flow of water (for example, for power generation) is not entitled to waste water or to use it unreasonably. (City of Barstow v. Mojave Water Agency (2000) 23 Cal.4th 1224, 1241-1242, 99 Cal. Rptr.2d 294, 5 P.3d 853.) The owner of a common law right