Field Report: June 28, 2019

The water in Suicide Basin has gone up by 7 m (~1 m per day) since our last site visit on 21 June. On Friday afternoon, the surveyed lake level was at 427.75 m, which is ~10 m below the lowest point of the dam. Given the very warm weather and thus increasing filling rates over recent days, dam overtopping may start in early July.

This is only a rough estimate for the timing of the subglacial lake drainage, since the lake may drain before or after overtopping. If the basin filled all the way, the drained volume should be slightly lower than last year’s event, assuming that the lake will drain to the same level as last year.

Note that the peak flow at Mendenhall River depends not only on the total water volume drained from Suicide Basin, but also on how fast the water drains from the basin (the faster, the higher the peak) and how high the Mendenhall River baseflow will be during drainage.