Unimpaired Runoff Calculations[*]

Flow readings from river gages are influenced by upstream diversions, impoundments, and other manmade alterations. The natural runoff at a gage is reconstructed by removing the effects of these "impairments." This calculation is done on a monthly basis for all major rivers in the state, and on a daily basis for a subset.

The result is the "full natural flow," expressed as a rate (in Cubic Feet Per Second [CFS]), or as a volume over a fixed time interval, Acre-Feet (AF). Generally, "thousands of Acre-Feet" (TAF) is used. Our convention is to use "TAF" rather than "KAF," which would designate kilo-acre-feet.

Monthly computations

Unimpaired runoff is computed on a monthly basis at 36 locations around the state.

• Seasonal Flow Summary: Current | Previous
• Monthly Flow Summary: Current | Previous
• All full natural flow reports from CDEC

  Daily computations

  Daily unimpaired runoff is computed for several major gages. These values are much less accurate because not all data is available on a daily basis. The corresponding monthly values will be different.
  

• Daily Flow Summary: Current | Previous
• Daily Total Unimpaired Runoff (in Thousand Acre-Feet)
• All full natural flow reports from CDEC

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  California Cooperative Snow Surveys