The hydrological effects of the underground nuclear explosion, CANNIKIN, were monitored by a network of streamflow stations and ground-water boreholes located on Amchitka Island.

Continuous records were obtained from six surface-water stations that range from 1.50 to 14.07 km from surface ground zero (SGZ). Confined fluid pressures in boreholes were recorded at five stations with slant distances ranging from 2.14 to 14.11 km from ground zero (GZ). Fluctuations of water level were measured in one open hole 6.42 km from GZ.

The stream system draining the CANNIKIN site lost 96 per cent of its flow within hours after the explosion. Lakes formed near SGZ remain low in stage and appear to be providing infill water for the rubble chimney. Measurements in boreholes also showed that the ground-water gradient was toward the explosion site. The response of confined fluid pressures was recorded in a number of boreholdes, and a relationship between maximum fluid pressure, P, and slant range, Rs, has been established as P = 920 Rs−2.10.

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