Over-appropriated
A basin in which the total volume of water rights on paper exceeds the water the basin physically produces in a typical year.
Over-appropriation is the normal condition of western basins, not the exception. Rights were issued over more than a century against optimistic assumptions about average yield, and the sum of them frequently exceeds what the river delivers in most years.
In an over-appropriated basin, seniority is everything and junior rights are structurally unreliable. It is also the condition under which basins get closed to new appropriation, which turns existing rights into the only available supply and reprices them accordingly.
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