hybrid system with riparian water rights. In Oregon, landowners have rights to water on their own land at a certain time at which it is then incorporated into the appropriation system. Adoption Alaska, Arizona, California, Colorado, Hawaii, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Texas, Utah, Washington, Wyoming all use the prior appropriation doctrine, with permitting and reporting as their regulatory system. Of these, California, Texas, and Oregon recognize a dual doctrine system that employs both riparian and prior appropriation rights (see ). Eight states (Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming) engage in prior appropriation without recognizing the riparian doctrine. However, prior appropriation does not always determine water allocation in these states because various federal regulations also have priority over senior users. For example, the Endangered Species Act of 1973 seeks to protect animals at risk of extinction, so a senior user's rights may be restricted in favor of federal regulation protecting the habitats of endangered animals. These federal rules manifest as a prior allotment by the Secretary of the Interior. Arizona Arizona adopted the prior appropriation doctrine such that a person could acquire this water right simply by applying it to beneficial use and posting an appropriation notice at the point of diversion. On June 12, 1919, they enacted the Public Water Code in which the person must apply for and obtain a permit for water use. Colorado The appropriation doctrine was adopted in Colorado in 1872 when the territorial court ruled in Yunker v. Nichols, 1 Colo. 552 (1872), that a non-riparian user who had previously applied part of the water from a stream to beneficial use had superior rights to the water with respect to a riparian owner who claimed a right to use of all the water at a later time. The question was not squarely presented again to the Colorado Court until 1882 when in the landmark case, Coffin v. Left Hand Ditch Co., 6 Colo. 443 (1882), the court explicitly adopted the appropriation doctrine and rejected the riparian doctrine, citing Colorado irrigation and mining practices and the nature of the climate. The decision in Coffin ruled that prior to adoption of the appropriation doctrine in the Colorado Constitution of 1876 that the riparian doctrine had never been the law in Colorado. Within 20 years the appropriation doctrine, the so-called Colorado Doctrine, had been adopted,