Abstract
Since the mid-Edo period, serious conflicts over agricultural water use during periods of drought have continuously occurred between new farmers upstream and established farmers downstream in the large river plains of Japan. Applying a non-cooperative sequential game theory, this study analyzes the above conflicts and the establishment of upstream priority custom. The models considering the conflicts cost makes clear why downstream groups could rationally choose to accept upstream priority when no political pressure could be brought to bear on the cause of upstream groups, and how the downstream groups could protect their water rights when the cost of preventive measures such as watch and guard on the operation of upstream intake facilities were less than damages inflicted by a drought. It has been definite that Game Theory is useful in analyzing the social structure of water use conflicts.
