Idaho Code § 42-903
Any person, association or corporation delivering or distributing water under any fixed annual charge or rental shall provide the necessary gates and measuring devices to render possible and practicable a measurement of the quantity of water being delivered to any consumer (or number of consumers using a common lateral or distributing ditch); and the price charged for the annual use of the water so distributed shall be in proportion to the quantity of water delivered from the works of such person, association or corporation. Such measuring devices shall be of such a character, and provided with such gauges or scales, that the quantity of water being delivered at any time can be ascertained by inspection; and shall be of such general plan as shall meet with the approval of the department of water resources, which shall inspect any such devices whenever possible to ascertain their character, and the department shall furnish such general information and instructions to any consumer, or the watermaster of any number of consumers of water, as may be necessary to enable him to ascertain the quantity of water flowing through any such measuring device.
Idaho Code § 42-903