Recent field investigations in Yap, Federated States of Micronesia, undertaken to document ancient fresh water management practices and their physical manifestations, are reported. Project findings include an indigenous technological tradition of fresh water management designed to provide water for domestic uses and to prevent erosion and minimize soil loss from agricultural plots under variable climatic conditions. The fresh water management system consisted of household catchments, remote seeps, springs and streams, taro patch wells, and a complex system of diversion canals and drainage ditches. Although the field work was focused on Map Island in northern Yap, the spatial extent of this system is co-extensive with the entire Yap island complex of ca. 30 square miles, encompassing both upland and lowland topography.

Customary practices involving differential status ranking regulated individual access to fresh water sources. A conservation ethic prevailed with regard to agricultural soils and fresh water. Present use patterns resemble those of the prehistoric past; however, access now is less strictly regulated and the physical system has deteriorated markedly due to an inadequate labor force for maintenance and repair. This lack is due to dramatic population losses after European contact in the early 19^th century and subsequent colonial occupations through the second world war. Current and future demands on traditional fresh water sources for domestic consumption appear not to threaten traditional agricultural practices but modernization of water delivery systems is encouraging higher usage rates in households.