[saltcured]

As I recall, the watershed for Lake Tahoe is actually very small, because the surrounding ridges are quite close to the lake. The surface of the lake is the majority of the total collection area for precipitation.

To me, this suggests that evaporative losses may also be a significant portion of the draw-down you see each year, i.e. precipitation and evaporation on the same surface area. A trend towards more rapid reductions in water level may say something about climate shift, with hotter and drier summer conditions?

[ericbarrett]

Perhaps also reduction of watershed area because of development and capturing of waste water? I know there are mitigation efforts around the usual farm and garden runoff (nitrogen etc.) for Tahoe; lack of such mitigation why Clear Lake[0] is a soupy green.

[0] https://en.wikipedia.org/wiki/Clear_Lake_(California)