Abstract:
This paper presents a rain duration-dependent procedure based on the popular
Soil Conservation Service Curve Number (SCS-CN) methodology for computation of
direct surface runoff from long duration rains. Curve numbers are derived from long-term
daily rainfall-runoff data, and antecedent moisture condition (AMC) related with antecedent
duration. Analysis of data from five Indian (large, in terms of area) watersheds reveals the
calculated curve numbers to decrease with the considered duration, showing the existence
of a characteristic value of minimum CN or maximum initial abstraction to occur in a
watershed for a pre-selected AMC. The testing of the proposed procedure on the separate
(measured) rainfall-runoff event data sets from the same watersheds suggests satisfactory
workability of the method.
