[1] Waters and Water Eights—Prescription—Excessive Diversion. One actually diverting water under a claim of appropriation for a useful or beneficial purpose cannot by such diversion acquire any right to divert more water than is reasonably necessary for such use or purpose, no matter how long a diversion in excess thereof has continued.

1. Correlative rights of upper and lower proprietors -as to appropriation of water, note, 41 L. R. A. 743-; right of prior appropriator, note, 30 L. R. A. 665, 668.

[2] Id.—Amount of Water Necessary—Weight of Opinion Evidence.—In determining whether the amount of water in fact used on a given acreage was applied to a beneficial use and was reasonably necessary for irrigation and the other purposes to which it was devoted, the testimony of farmers, and of superintendents, ■ditch-tenders, stockholders, irrigators, and the presidents and directors of the various irrigation systems, whose actual knowledge of the lands and the use of water thereon has extended over a period of years, is of a higher quality than the mere opinion of experts who have made a mere casual or theoretical survey of the lands.

[3] Id.—Presumption in Favor of Prior Appropriator.—In determining how much of the water in fact used on a given acreage was reasonably necessary for the purpose for which it was used, a court should be liberal with the appropriator to the extent, at least, that it should not deprive him of any portion of the amount of water that he has in fact used- for the period necessary to gain title by prescription, unless it is clearly and satisfactorily made to appear that he has used moi;e than was reasonably necessary.

[4] Id.—Conflicting Rights to Waters — Erroneous Rulings of Trial Court—Prejudicial Conduct—Preponderance of Evidence —New Trial.—In these actions involving the rights of various companies to divert water from a given river for irrigation purposes, the various rulings of the trial court with reference to the admission and rejection of evidence, standing alone, were such that they might have been regarded as without prejudice, but when coupled with the conduct of the trial judge and the fact that the evidence preponderates in favor of appellant, were such that the interests of justice demanded a new trial.