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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.
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.
California Cooperative Snow Surveys