Water Resources Management

, Volume 20, Issue 5, pp 643–660

An Improved IaS Relation Incorporating Antecedent Moisture in SCS-CN Methodology

  • S. K. Mishra
  • R. K. Sahu
  • T. I. Eldho
  • M. K. Jain


Employing a large dataset of 84 small watersheds (area = 0.17 to 71.99 ha) of U.S.A., this paper investigates a number of initial abstraction (Ia)-potential maximum retention (S) relations incorporating antecedent moisture (M) as a function of antecedent precipitation (P5), and finally suggests an improved relation for use in the popular Soil Conservation Service Curve Number (SCS-CN) methodology for determination of direct runoff from given rainfall. The improved performance of the incorporated M = α \(sqrt{P_5S}\) and Ia = λ S2/(S + M) relations, where λ is the initial abstraction coefficient, in the SCS-CN methodology exhibits the dependence of Ia on M, which is close to reality; the larger the M, the lesser will be Ia, and vice versa. Such incorporation obviates sudden jumps in the curve number variation with antecedent moisture condition, an unreasonable and undesirable feature of the existing SCS-CN model.

Key words

antecedent moisture curve number initial abstraction NEH-4 soil conservation service 


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Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • S. K. Mishra
    • 1
  • R. K. Sahu
    • 2
  • T. I. Eldho
    • 2
  • M. K. Jain
    • 3
  1. 1.Department of Water Resources Development and ManagementIndian Institute of TechnologyRoorkeeIndia
  2. 2.Department of Civil EngineeringIndian Institute of Technology BombayMumbaiIndia
  3. 3.National Institute of HydrologyRoorkeeIndia

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