“capacity-per-foot-of-height is always slightly greater the higher the lake levels rises because all lake valleys are wider and longer as the lake level rises”
That is a very good point. This is not the water rising in a fixed swimming pool - it is varied terrain. Before reaching 175, or 181 meters, the water might spill over into other areas upstream - maybe huge catchments will have to flood, before the water can get that high.
Bump.Praying for these people.