Evaluation of the Surface Runoff Estimated by the Mexican Official Standard and SCS-Cn Model in Two Small Basins in Mexico

Abstract

The determination of the surface runoff depth in the microbasins of Mexico is carried out by estimation methods whose degree of accuracy is unknown, due to the information about temporal evolution of the precipitation and direct surface runoff is scarce. For this reason, it is necessary a revision of the accuracy of the available methodologies to estimate surface runoff for ungauged basins in order to identify the most appropriate for the mexican conditions. The aim of the present work was the evaluation of the Mexican Official Standard (NOM) and the Soil Conservation Service Curve Number (SCS-CN) methodologies to estimate the surface runoff depth in the microbasins Rio Chapingo and El Malacate, which are located in the state of Mexico and Michoacan respectively, with the measured information of precipitation and direct surface runoff of two recent years. With the SCS-CN method, the CN values were extracted by two ways: (1) with the tables of National Engineering Handbook (SCS-CN-NEH); and (2) with asymptotic functions (SCS-CN-AF) that associate the CN with precipitation, using ordered pairs method. According to the values of the statistics measures AE (mm), RE, RMSE (mm) and Nash-Sutcliffe index (NS), the best method in both basins was SCS-CN-AF (Rio Chapingo: