The United States Geological Survey maintains a nationwide network of stream monitoring stations. These stations report in real time and USGS has a public access website for sharing this data. The map below shows relative stream levels for August 23, but on the website the map is updated in real time. Each dot represents a monitoring station and clicking on a dot at their website will take you to a webpage for that station with hydrographs and much more information.
Access the USGS data at WaterWatch