The original walls, dating from 250 BC, consisted of tree trunks latched in triangular sections to hold bamboo baskets with boulders inside. The walls served to divert river currents for irrigation. (Cf. Science and Civilization in China, Needham, vol. 4, part 3, p. 289.). The box holding the model also includes printouts of an email from Dr Sumet Jumsai and copy photographs of a full-size spill way wall.