THE USE OF BOREHOLE VIDEO IN INVESTIGATING THE HYDROLOGY OF A TEMPERATE GLACIER

A GeoVision Micro(R) colour video camera was used to investigate the i nternal structure of 11 boreholes at Haut Glacier d'Arolla, Switzerlan d. The boreholes were distributed across a half-section of the glacier , with closest spacing towards the glacier margin. The boreholes were used to investigate the hydrology of the glacier through automatic mon itoring of borehole water level and electrical conductivity (EC) at th e glacier bed. EC profiling was undertaken in several boreholes to det ermine the existence of water quality stratification. Temporal variati ons in EC stratification were used to infer borehole water sources and patterns of water circulation. Borehole video was used to confirm the conclusions made from these indirect sources of evidence, and to prov ide an independent source of information on the structure and hydrolog y of this temperate valley glacier. The video showed variations in wat er turbidity, englacial channels and voids, conditions at the glacier bed and down-borehole changes in ice structure. Based on the video obs ervations, englacial channels accounted for approximately 0 . 1% of th e vertical ice thickness, and englacial voids for approximately 0 . 4% . Overall, the video images provided useful qualitative and semi-quant itative data that reinforce interpretations of a range of physical and chemical parameters measured in boreholes.