I found this on the web under "US Coast Guard flare requirements...
"All vessels used on coastal waters, the Great Lakes, territorial seas, and those waters connected directly to them, up to a point where a body of water is less than two miles wide, must be equipped with U.S.C.G. Approved visual distress signals. Vessels owned in the United States operating on the high seas must be equipped with U.S.C.G. Approved visual distress signals."
Am I correct in reading this as meaning I don't need flares on the Snake River? While I can get to the Pacific from here, the river is considerably less than 2 miles wide at many points long before it gets here. I also take it to mean that they're not required on inland lakes other than the ones listed.
I'm not saying they wouldn't be a real good thing to have just that they may not be required to pass an inspection. (that could explain why in my annual CG aux. inspection here I've never had my flare kit looked at).
I've often wondered what my liability would be if I fired a flare on the river and it wind drifted onto the tinder dry river bank. 😱