Effects of land use on runoff curve numbers.

The Runoff Curve Number method is a widely used and accepted technique for modeling runoff in ungaged watersheds. Input variables for this method include soil type, watershed condition, land use and cover density. The land use variable was isolated and evaluated at 3 scales (local, regional and national) using rainfall-runoff data from 177 small watersheds around the United States. Curve Numbers were calculated for each land use at each watershed. Differences at the 5% significance level were found in land use Curve Numbers at all three scales. Meadow usually produced the lowest Curve Number at the local and regional level. No difference could be determined between pasture and range at the regional level. At the national scale forest had the lowest Curve Number, meadow was second lowest and brush Curve Number was highest. No difference could be determined between Curve Numbers from row crops or small grain at any scale.hydrology collectio