BuRec emptied all the other lakes in No. Calif. this year to keep water in Shasta for the salmon. So Folsom and the others are headed for historic lows (and possibly dead pool; a pump barge is being set up at Folsom to get water into the urban water intakes that will be exposed once the lake drops another 10 feet or so), which has hurt other fisheries and the farmers along the upper Sacramento, who lost a lot of their allocations that usually come from Shasta.

If you want to look for old bridges (or at least bridge piers), concentrate on the foothill lakes. It might be possible to follow some of the Yosemite Valley, for instance, that's usually underwater in Lake McClure.