I want to thank all the people who supported me through the writing of this thesis, in one way or the other. Special thanks go to:
Professor Erhard Hoffmann and Professor Hermann Hahn from the Siedlungswasserwirtschaft department, Universität Karlsruhe (TH), and Luis Carlos García, director of Noetrópicos, for their teaching, guidance and orientation.
Rosa Emilia Querubín and Luis Eduardo Alvarez from Aguas del Puerto, Luis Fernando Ramírez from Conhydra, and Juan Carlos Carvajal from the Planning Office of Puerto Berrío, for the tour and the information supplied during the field visit.
Lecturers Alvaro Wills from the Universidad de Antioquia, Francisco Toro and Jaime Polanía from the Universidad Nacional de Medellín, and Luis Alejandro Camacho, from the Universidad Nacional de Bogotá for their ideas and orientation during the planning phase.
Profesor Emil Dister for facilitating the initial contact with Luis Carlos García and Neotrópicos.
Lucía Estrada from ISAGEN for the supply of the water quality monitoring data.
Diana Jaramillo from Corantioquia, Alejandra Galeano from Cormagdalena and Hebert Rivera from IDEAM for their good will to help.
Mario Jiménez, PhD. student from the Universidad Nacional de Medellín, for the supply of useful bibliography.
Patrick Koska for his assistance with the computer software and Paulina Alfaro for the editing and corrections of the final version of this document.