A waterfall's flow isn't fixed. It comes from a creek or river upstream, and how much water is moving depends on what fed that watershed recently — snowmelt, rain, or the lack of either. The same waterfall that looks like a wall of whitewater in April can be a thin ribbon, or nearly dry, by late August. Neither photo is "wrong" — they're just different seasons.
Most waterfalls in the continental U.S. follow a broad seasonal curve: flow builds through winter and peaks during spring snowmelt (roughly March through June, later at higher elevation), then tapers through summer as snowpack runs out and rain becomes less frequent, hitting its lowest point in late summer and early fall. Waterfalls fed by a glacier or a large, steady spring behave differently — they can hold a strong flow through summer because their source doesn't depend on recent rain. A waterfall fed only by a small seasonal creek can slow to a trickle or stop entirely in a dry summer.
On Waterfall Scout, a listing's "Flow / best time to visit" note only appears when the waterfall's own managing agency documents a seasonal pattern for that specific spot — we don't estimate this ourselves. Right now, 29 of our 108 listings have an official note like this. When a listing doesn't have one, it usually means the agency hasn't published anything about seasonal flow — not that the waterfall is reliable year-round.