The gage for the South Fork (Deckers run) is right at the base of Cheesman Damn, some 15 or more miles upstream of Waterton. The gage for the North Fork (Foxton run) is near the Town of Bailey I think, which is some 20 or more river miles above Waterton. There is lots of tributary area to collect snow melt and rain before hitting the Waterton gage. I personally have seen the drainage along Foxton Road dumping somewhere around 50 cfs (my estimate given culvert size) into foxton right above the granite pool drops section that ends in the pretty good surf wave. This is a relatively small basin compared to Buffalo Creek, Deer Creek, and the steam that dumps in near Deckers.
Once runoff and spring rains stop, the gages will be more accurate when combined and compared to Waterton. Until then, we can appreciate the added flow. Later.