Soil Moisture and Runoff?Another Look

by Joseph A. Van Mullem, Soil Conservation Service, Bozeman, United States,

Document Type: Proceeding Paper

Part of: Irrigation and Drainage: Saving a Threatened Resource?In Search of Solutions


Infiltrometer studies conducted on numerous soil types in various locations of the United States which had soil moisture data were used to calculate the runoff Curve Number (CN) of both the dry and the wet condition. The CN value under wet conditions was found to average seven to 18 higher than for the dry condition. This increase in CN was not correlated to the increase in soil moisture in this study. Several past studies support the conclusion that the soil moisture effect on runoff volume is small. Several hydrology computer models use soil moisture as an index to account for all of the variability in CN described by the Soil Conservation Service (SCS) as antecedent runoff condition (ARC). Runoff predicted by these models could be significantly biased by the soil moisture adjustments to CN.

Subject Headings: Soil water | Runoff | Computer models | Hydrologic models | Mathematical models | Hydrology | Soil properties | United States

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