Yesterday my wife and I went to swinging bridge res. 2 1/2 years ago they found a sink hole in the dam, so they drew it down by 70% while under repair. It also changed ownership, which slowed progress. This res was a fishing heaven before this happened. Strong population of smallies, nice walleye, some of the biggest crappie I've ever caught. I don't know what I expected, but the fishing was really tough. I think the food chain was severly impacted, from insect life up to predatory fish. I caught a few smallies, but nothing like before. I'm guessing it will take a couple/few years for the system to right itself. The water levels are still rising as it fills to normal pool.

  Anyone experience this kind of thing, and if so, how long should I expect the system to re-establish itself?

Could be right away, could be never.

One local reservoir was almost completely drained due to dam construction and a severe drought.  It was down for a little over a year.  Fishing this summer (second year of being full/almost full) has been good.

I recently fished a 7 and 1/2 acre lake that was newly built.  It had bass around 8-10 inches and catfish around 12 inches.  It's all about resetting the the food cycle , everywhere from the zooplankton, to the minnows, smaller gamefish, and then larger gamefish.  I'd give it a little bit of time and it will probably establish itself again.