In May of 2001 "The Nail" was pounded into a permanent pier at the water level. This was declared to be the 0 level of the lake. Despite its arbitrary nature, the nail has proved to be a reasonable reference point for the lake level. Measurements are taken at the beginning of each month. A few years after the nail was joined to lake water, crevice corrosion took its toll and the nail was replaced with a screw. The screw is still referred to as "The Nail" to avoid any confusion. Some data points, especially those in 2009 and 2010, were estimated by scanning the archive pages. Apparently taking an actual measurement during this time period was too depressing. I still have nightmares.
The North and mid sections of the lake are less affected by low water levels than the South end.
By 2016, Lake Lucerne had recovered from a drought. The Lake was still about 6 inches below the nail.
In 2018, the lake had fully recovered from the lows to go to 24 inches above the nail.