You know, I saw short drops and spikes in the water flow during my review of these tables the last month and I think they may be where smaller lakes above shut down their outflow or turn up or down a turbine.
Quite possible, likely even. PG&E owns some of the upstream generation, and they will regulate output to a schedule just as we do at TVA. All depends on the power load curve and other priorities (lake levels, river levels, etc.).
There are many reservoirs in the Feather River basin.
http://www.sacriver.org/aboutwatershed/roadmap/watersheds/feather/upper-feather-river-watershed
Frenchman Lake is a 25 minute drive from my home. Snow is very deep(in the typical places) and the lake is full.