Hey @AngelaStemen, I know your post has been around a while with no answers, but I can do my best. Whether a stream exists year round (annual) or at only intermittently (perennial) is going to depend entirely on the area you're working in. There are many factors that contribute to a stream's existence. You can use flow accumulation to get a good idea of the annual stream set, but there are always going to be other factors you'll need to consider. I'm guessing this problem is long solved, but for the future, the ESRI team has made flow accumulation a *lot* easier to understand. I'd check out this resource to learn more.
