Vented pressure sensors going to a logger box out of range of flow is one option, Ultra sonic distance measure is another, which avoids problem of freezing etc. Both could easily give you continuous, real-time measures which you may find much more valuable than peak stage only. Not sure about your budget, but driving to all the stations each time for peak stage seems costly. Go to the Blog section on this site, then under catagories, select Gadget Showcase. Page through and check out the Ultra sonic setup Shannon Hicks has been working on. Hope this helps.