Troutnut is indeed an excellent site.
You might want to contact these folks--- they might help you with some advice on setting up the study, survey techniques, things to consider, resources like species distribution maps, suggest keys for identification etc. And it sounds like a great project for a grad student or two:
Dept. of Entomology at the Rutgers School of Environmental and Biological Sciences
Roger Rohrbeck's site, Fly Fishing Entomology might be useful also. He has an identification key for adult caddis, mayflies, and stoneflies that can help narrow down possibilities. And his "links" page has a bunch of links to taxonomic keys for ID-ing including pdf files on mayfly nymphs etc.
Good luck with your project -- keep us in the loop I'm sure there are a lot of other folks--- including me--- that would really like to hear about your progress on the project and your findings.