Riparian rights are the rights of persons who own land bordering a river, bay, or other natural surface water. A riparian right entitles the property owner to the use of both the shore and the bed as well as the water upon it. Such rights, however, may not be exercised to the detriment of others with similar rights to the same watercourse. As Sir William Blackstone observed in his Commentaries on the Laws of England (1765–69), "If a stream be unoccupied, I may erect a mill thereon, and detain the water; yet not so as to injure my neighbor's prior mill, or his meadow; for he hath by the first occupancy acquired a property in the current."

Riparian rights, or riparianism, is a legal doctrine used in the eastern United States to govern water claims. Riparian landowners have rights to the use of the water adjoining their...