Comparación de Tasas de Reaireación (Ka) en Ríos Andinos Colombianos Frente a Ecuaciones Empíricas para Modelos de Calidad del Agua

Abstract

This study presents a literature review of case studies at the river section level in Colombian Andean rivers, linking water quality modelling with the experimental determination, calibration and application of the kinetic rates of deoxygenation (K_1 o K_d) and re-aeration (K_2 o K_a) as fundamental parameters of the Streeter-Phelps model and its derivatives, such as the SAG curve or other more complex water quality models, which likewise use the Streeter-Phelps equations to determine DO. The various approaches reviewed address the experimental determination of K_a using tracers such as SF₆ and Rhodamine WT in Latin American mountain rivers; the estimation of carbonaceous deoxygenation constants from final carbonaceous BOD data and hydraulic parameters measured in the field; the calibration of models such as OTIS, QUAL2K and HEC-RAS with local data; the critical comparison of empirical predictive equations of North American and European origin against the hydraulic conditions typical of Andean rivers; and the integration of these models with comprehensive river basin management tools such as the River Basin Management Plans (POMCA) and the water quality objectives programs established by the Regional Autonomous Corporations for surface water bodies. A systematic review of the literature shows that the Ka values measured experimentally in Colombian Andean rivers significantly exceed those predicted by classical empirical equations of North American and European origin, confirming the unsuitability of these models for high-mountain hydraulic conditions. In Colombia, water quality objectives constitute the technical and regulatory instrument through which the Regional Water Authorities (CARs), the Secretariats of the Environment and local councils define, for each river basin section, the maximum permissible BOD values and the minimum permissible dissolved oxygen (DO) levels, the correct formulation of which depends on water quality models with reliable kinetic parameters. The Ka database for Colombian Andean rivers remains scattered and lacks altitudinal regionalization, which represents the main gap identified and the most urgent area for future research to strengthen integrated river basin management.