Field Report: June 21, 2019

The water in Suicide Basin has gone up by 14 m (~1 m per day) since our last site visit on 7 June. On Friday afternoon, the surveyed lake level was at 420.35 m and thus ~18 m below the lowest point of the dam. Based on filling rates from previous years, dam overtopping may start around 12 July—see graph on the new NOAA website.

This is only a rough estimate, since the lake may drain before overtopping and since filling rates may change from day to day. If the lake drained at the current level, the GLOF volume may be on the order of two-thirds of the 2018 event. If the basin filled all the way, the drained volume should be slightly lower than last year’s event. These estimates assume that the lake will drain to approximately the same level as last year.

The peak flow at Mendenhall River depends on the total water volume drained from Suicide Basin, however, it also depends on how fast that water drains (the faster the drain, the higher the peak) and how high the Mendenhall River baseflow will be during drainage. The latter factors are challenging to predict far in advance.

The water level surveyed on Friday (420.35 m) was close to the water level derived from the Nupoint timelapse photo (420.5 m using the 6:00 am image).

We measured ~0.6 m ice melt over the last two weeks. This ice melt further lowered the elevation of the ice dam (lowest point at 438.5 m as of Friday afternoon). There is a moulin right before that low point and it will be interesting to see how the moulin will interact with the rising water level.
The capture interval of the USGS time-lapse camera was changed to 12 hours (6:00 am and 6:00 pm). This change should take effect on Monday.