Using the drone-based elevations models from last year, we derived an approximate vertical scale for the rock face on the north side of the basin. This scale is plotted on top of the telemetered photos and gives an approximate idea about the ice/water elevation in the absence of telemetered water level measurements.
By translating/rotating the 2019 images into the 2018 image coordinate system, the water level can be checked independently, taking advantage of the fact that for each image taken in 2018, we have a corresponding water level measured by the gages. This morning, the water level was at about 405 m a.s.l., which matches the values from the scale (figure to the left) pretty well.
I used the same approach (translate/rotate the 2017 image into the 2018 image coordinate system) to determine the peak level of the 2017 lake (which never reached the gauge). It looks like that peak was reached on May 30 at 407.8 m a.s.l. (about 3 m above today’s level).
Using the above methods, we can measure the current water level within +- 1 m, which is sufficient for real-time monitoring. Things get more complicated once the water level is high, since we can’t see the water in the back of the basin anymore.
Below the lake volume lookup table I mentioned, which provides likely lake volumes for different Pre-GLOF and Post-GLOF water level combinations: