I didn't think any of you codgers were still allowed to have pie, unless it's sugar-free, and I refuse to buy that. I could bring you some rice cakes, probably.
On topic, lower blood pressure can be a sign of severe dehydration; mild dehydration causes blood pressure to go up. From the sound of the OP, he put down over a gallon at a ~15mph pace. I don't think hydration is much of an issue here.