This Wolfram-Alpha widget calculates the surface runoff (mm) based on the value of precipitation (mm) and the Natural Resource Conservation (NRCS) Curve Number (CN).  More information on the methodology can be obtained from the following reference:  Fangmeier, D. D., W. J. Elliot, S. R. Workman, R. L. Huffman, and G. O. Schwab, 2005. Soil and Water Conservation Engineering, Fifth Edition. pp. 528.  Values of CN for various land covers, soils and antecedent moisture conditions are available in the NRCS Pond Construction Handbook.  Click here to download

Note to user:  Sorry about all the digits to the right of the decimal point.  I couldn’t find a way to control this when creating the widget.

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