No go on causey

[wiperhunter2]

I was fishing it last year on Dec 21 and I can tell you it is much lower than it was last year at this time, I guess it could be 28 vertical feet low but that would really surprise me. I wonder how they came up with estimate

Here is the link to the BOR site.  The level is not an estimate, it's from a level transmitter.

https://www.usbr.gov/uc/water/hydrodata/...elevation/

Any idea how this transmitter works? Does it work off of pressure? Because I have never seen a float of any kind, in the water there or any
 type of marker on the side of the rocks so they would know the level. I just go by sight and how far I have to walk down the face of the dam to get on the ice.