California Hydrologic Data Sources

California Precipitation Data

• Realtime and Historical Precipitation Data (California Data Exchange Center)
• California Snow Surveys (Dept of Water Resources)
  
  
• National Climatic Data Center On-Line Data Access
• NCDC On-Line Monthly Precipitation Data
• NCDC Climate Visualization
• NCDC US Summary of the Day Graphing

California Streamflow Data

• California Streamflow Data Archive (USGS gages)
• Current California Streamflow Data (selected USGS sites)
• Realtime and Historical Streamflow Data (California Data Exchange Center)
  
  
• Humboldt Co Streamflow Data Archive (USGS gages)
• Current Mad R at Arcata Discharge (CDEC realtime)
  
• Current Mad R at Arcata Discharge (USGS Realtime)
• Northwest California Rivers and Rain
• North Coast River Forecast (NWS)
  
• USGS Water Resources of California
• USGS Current California Conditions
• USGS California Hydrologic Report
  
  
• USGS Surface-Water Data Retrieval (other states)

Other California Surface Water Data

• USGS Water Resources of California
• California Rivers Assessment
• EPA's Surf Your Watershed

California Groundwater Data

• California Groundwater Atlas (USGS)
• California Well Levels (Dept of Water Resources)