What are you going to allow to grow around the pond, if anything? You'll have to contend with cottonwood saplings and cattails as long as the pond's there, unless you plant something else to shade the area. I've seen Quercus nigra used around here, but I don't think they'll grow that far north.
Stagnation is a serious problem, but you seem to be thinking about flow control. Do you have a small creek handy to keep pumping in fresh water, or will you have to hook into the local water supply? Could get expensive on the meter. I was going to say you could rely on the water table, if it's shallow enough, but the liner's going to isolate you from that. And since you mentioned a liner in the first place, I'm guessing that creek isn't handy...
Oh, and you'll also have to plan what you want to grow in it. That can help with the stagnation problem. But I don't know much about aquatic micro-ecosystems.
And that's most of what I know about ponds.
SP, you've finally gone over the edge. The heat must have gotten to you.
