Runoff Curve Number (CN model) Evaluation Under Tropical Conditions.

In tropical countries the Curve Number method (CN) of the Soil Conservation Service (SCS) is widely used in civil engineering (to calculate drainage infrastructure) as well as in agricultural and environmental studies. However, little is known about the accuracy of CN method in tropical watersheds. To reveal this accuracy, this study compares the SCSCN model with the methodology proposed by Hawkins (1993) where CN (CNQ) values are determined with field data measured in an Andean micro-basin. For this, CN values for the tropical micro watershed "La Vega" were identified using the tables proposed by the SCS and its respective antecedent moisture and slope corrections (CNAMC2S); subsequently CNQ values were derived from 55 events in which runoff and rainfall were measured. According to the results obtained, it was found that in the tropical micro watershed evaluated in this study, the SCS-CN model overestimated runoff. The SCS-CN model is strongly influenced by the antecedent humidity and its impact becomes stronger in high rainfalls records; however, the antecedent humidity influence was not observed in measured runoff data. Despite the SCS-CN model did not show a direct relationship between CN and rainfall, this relationship was observed in measured data. Furthermore, a clear relationship between runoff and maximum rainfall intensity was found, so it is considered that including this factor in future research can improve the model's predictions. This study shows that SCS-CN model has some inaccuracies and it requires further studies to know its applicability in tropical conditions. [ABSTRACT FROM AUTHOR]