Introduction

River water quality modeling is a useful tool in the description and prediction of changes in the characteristics of a river system. It is commonly used for determining and forecasting changes in the water quality parameters caused by the discharge of point and non point sources. The aim of the present study is to assess, by means of a water quality model, the local effects on the water quality of a branch of the Magdalena River caused by the wastewater discharged by the municipality of Puerto Berrío, Colombia.

The Magdalena River is the largest and most important river in Colombia. Almost 50% of the country’s population lives on the river basin, including at least 25 urban centers located on the riverside. One of these municipalities is Puerto Berrío, and just as in many others, the wastewater produced there is discharged into the river without any previous treatment, entailing a series of negative effects, both at the global and the local level.

The methodology used for the present study was mainly based on two procedures: the collection of secondary data, including a field visit to the study area, and the data processing by means of two water quality models. The chosen software for this was the Water Quality Model Computer Aided Learning, WQM CAL, developed by Géza Jolánkai, István Bíró (2001) for UNESCO. It includes several models, from which two were chosen in order to assess the effects of the wastewater discharges in terms of the oxygen household conditions (BOD-DO model) and of pollutants plume distribution (transversal mixing model). As a complement, a water quality index analysis was done. One of the most important aspects considered and emphasized in this study was the seasonal variation both in the hydraulic characteristics and the water quality of the river, and how they influence the magnitude of the resulting effects caused by the wastewater discharge.

The first part of the document gives the reader a background on regional and local information as well as an overview of the relevant institutional and legal framework, followed by a more detailed description of the water quality system of Puerto Berrío, including the wastewater discharges and the receiving water body. These two parts constitute the key information for the last two chapters of the study, namely the application of the water quality models and the water quality index, and the respective results and analysis.

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