C.R.S. § 37-84-108: Running excess of water forbidden.

(1) During the summer season a person shall not run through his or her irrigating ditch any greater quantity of water than is absolutely necessary for irrigating, domestic, and stock purposes to prevent the wasting and useless discharge and running away of water.

(2) A person using an irrigating ditch or ditch system may use a tail ditch to return water to the stream in variable amounts as necessary to facilitate efficient operation of the ditch and delivery of water to persons served by the ditch or ditch system. The state engineer shall not require the delivery of any minimum amount of such water, except as required by court decree. Nothing in this section limits the state engineer's authority to administer water rights to prevent waste.