Live USGS river-gauge tick, deterministic. Answers "what is the flow at this gauge right now", "is this river high or low vs this week". Returns the latest streamflow (discharge, cfs) and gage height (ft) for one USGS site plus the 7-day min/max range, reading count, site name and coordinates, straight from USGS instantaneous values. Unknown sites 404 before payment. No LLM, no key, public domain.