A high, enclosed site poses a practical question: how will the people inside keep supplied with water? Wunushan’s excavated reservoir gives that question a material answer. Archaeologist Li Xinquan describes it as cut into the rock. It is a different kind of construction from a wall, using removal to create a space that could hold a necessary resource.
The reservoir belongs in the same picture as houses and stores. A mountain position was useful only if life could be sustained within it. Water storage made the interior more than a place from which to watch the surrounding country; it helped make occupation possible. The rock-cut basin makes that practical requirement visible within the defensive enclosure.