The River Tables.
The River Maps.
(Note markers are color-coded: class I, class II, class III, class IV, class V, class "VI". Markers with a black star inside indicate rivers with a write-up.)
(Note streamflow gages are also color-coded: "interesting" flow, river is up in the last 2 days, uninteresting flow (or uncalibrated), only uncalibrated height readings available, no recent flow or height readings available.
(Note rain gages are also color-coded: means good rain yesterday, means little or no rain yesterday, and means recent measurements are unavailable.)
(Note further: Google labels a lot of towns/villages incorrectly)