Flow Measurement in the Los Apantes river using precipitation-runoff and Stream gauging methods

Abstract

The Flow measurement in water bodies is a fundamental activity in hydrological studies, as it provides insight into the behavior of water resources in a specific region. The objective of this research was to apply and compare two methodologies for estimating the flow of the Los Apantes River in the department of Ahuachapán, El Salvador. The precipitation-runoff relationship and a gauging campaign were used. The precipitation-runoff methodology was developed using SAGA GIS software, which allowed us to delimit the watershed, identify representative weather stations with Thiessen polygons, and calculate average monthly flows from available historical precipitation records (1990-2010). From this information, we obtained the river’s hydrograph. The gauging campaign consisted of direct field measurements using the section-velocity method, with the support of specialized equipment such as the AA cup wheel. The measurements were taken in June 2025. The results showed consistency between the two methods, indicating that the combined use of both methodologies allows for more reliable flow estimates, applicable both to contexts with historical precipitation data available and to specific field measurements.