The creekbed I had the question about in the other thread, is now "a go". This will be interesting, regarding the reservoir. I'm going to design the first 40' or so as a long narrow pool so that it's mainly-level course doesn't drain when the feature is shut off. Then, the next 70' or so, will slant downhill at a slight angle. I'm going to place the auto-fill float in a hidden valve box where the pump is, but I'm going to attach and adjust the auto-fill after the creekbed completely fills. So the auto level will be at the lowest level in the reservoir. That way, when the creek's timer shuts off the pump at night, the reservoir won't overflow by 50 excess gallons. The pond book by Nash and Hughes had a formula to measure creekbed water capacity, but it's based off a 3" deep flow. They must use huge pumps. I doubt that I'll see more than 1/2" deep going over small wiers in this thing.