Correlations between Rain and Runoff Amounts and Composition in Eastern South Dakota

Abstract

AbstractA correlation between a synthesized rainfall‐intensity factor and runoff from small plots with sparse cover was significant but explained less than half the variation in the data. Loss of PO4‐P, NO3‐N, NH4‐N, and K in runoff was significantly correlated to the runoff amounts, and the regression explained about 50 to 75% of the variation in the data. The unexplained variation in the regressions probably is due to antecedent plot conditions, such as the soil and the plant cover growth or decomposition stage. Time since an antecedent rain was not significantly related to runoff. Average runoff volumes and average losses of PO4‐P and NO3‐N per runoff event from different‐sized cultivated areas for 2‐ to 5‐year periods had a highly significant correlation. The regressions, based on runoff volume and not on watershed size, apparently could estimate PO4‐P and NO3‐N losses on other watersheds in eastern South Dakota.