As needs for water increase in the growing economy of Colorado, especially in urban areas, old priority uses will inevitably have to give way to new perceptions of beneficial applications. The prior use doctrine, although theoretically applicable to the values of the marketplace, has practical shortcomings when senior water rights are sold for a different use. Agricultural use of water, which consumes a large share of Colorado's water entitlements at a low economic benefit, may have to be curtailed in the future in favor of more valuable uses. The author presented a similar paper at the 1984 AWWA Annual Conference and Exhibition. Includes 17 references.