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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]

The Dagua river basin, in Colombia, is the most important source of water for the Valle del Cauca ecosystem, however, due to poor agricultural practices, it has been affected by water erosion. This study aimed at estimating soil erosion in the Dagua river basin, using the universal soil loss equation (USLE). The results show that most of the area presents erosivities that are between 1000-5000 MJ.mm.ha-1, corresponding to low and very low categories. On the other hand, erodibility ranged from 0.143 to 0.842 t. ha.h. MJ-1 mm-1 ha-1, which is framed in the categories from weak to extremely erodable, where the low to medium category predominates. Regarding soil losses due to erosion, it was found that more than 20% of each of the municipalities of Dagua, Restrepo, La Cumbre, and Vijes, showed high and very high erosion, particularly in the areas with bare soils and crops such as pineapple, contribute strongly, sometimes reaching over 1000 t ha-1 yr-1. Therefore, it is important to promote practices such as contour or contour planting, integrated crop cover management, land uses that integrate trees, and in more critical cases to consider ecological restoration processes. [ABSTRACT FROM AUTHOR]