The main difference (although that is not clear from the article) that this system is based on fixed proportions of usable water volume whereas water rights in

The main difference (although that is not clear from the article) that this system is based on fixed proportions of usable water volume whereas water rights in the Western US states are mostly setup in order of seniority and (at least historically) with no adjustment mechanism for usable flow. That means that if users with senior rights use up all the waters, junior rights holders and the natural river itself get no water.