What is the test for reasonable use of water rights?

In Joslin v. Marin Municipal Water Dist., supra, 67 Cal.2d at page 141, 60 Cal.Rptr. 377, 429 P.2d 889, the court noted the limited water resources available to the state, and that "conservation [must] be exercised 'in the interest of the people and for the public welfare.' " These cases, along with others which have been cited above, note the evolution of water rights from a concept of absolute right of use to one of comparative advantage of use. The fact that a diversion of [225 Cal.App.3d 571] water may be for a purpose "beneficial" in some respect (as for desalinization of lakes or generation of electric power) does not make such use "reasonable" when compared with demands, or even future demands, for more important uses.

(g) Excessive Mandates