This page at My Outdoor Buddy has many links to California and Oregon weather information including Weather Reports, Highways & Passes, Lake and Reservoir Levels, River Conditions, Coastal Waters Marine Forecasts and Conditions (including swell, wave height, interval, sea surface temperatures and surfing conditions) as well as Bar Cams and Tide Predictions all in one place.
This website from the National Weather Service has a wealth of information. Mouse over a particular gage to get a graph of the flow for the last four days plus the forecasted flows for the next five days. Precipitation data as well.
Continuously updated US flooding information from the National Weather Service shows observed flooding locations and statistics, flood warning areas, as well as current precipitation. See the real-time effects of the flooding via social media posts.
At this CDEC website, you can display river stage maps for current hour and the past two hours for the North Coast, Upper Sacramento, Lower Sacramento, Russian, Central Coast, San Joaquin, or Truckee rivers.
The Sacramento County’s ALERT system consists of 2 base stations, and 50 gauging stations. The purpose of the County’s ALERT website is to provide access to stage and rainfall information during storm events. Find streamflow, forecasts, and more here.
At this Department of Water Resources (DWR) website, you can display the latest floodplains in a web viewer. The data has been expanded to cover the floodplains to cover all counties in the State and to include 500-year floodplains. The 100-, 200-, and 500-year floodplains can be selected for display using this viewer. The web viewer allows users to view a particular area, identify their potential flood hazards, and print a floodplain map.