Design of Watershed Based Water Quality Monitoring The Case of Nitrate Pollution in the Aconcagua River, Chile Dissertation Zur Erlangung des akademischen Grades Doctor rerum naturalium (Dr. rer. nat.) Vorgelegt dem Rat der Chemisch-Geowissenschaftlichen Fakultät der Friedrich-Schiller-Universität Jena von Diplom Chemiker Lars Ribbe (M.Eng.) geboren am 28.06.1968 in Bremen Februar 2008 Gutachter: 1. Prof. Dr. Wolfgang Albert Flügel (Friedrich-Schiller-Universität Jena) -------------------------------------------------------------------------------------------- 2. Prof. Dr. Hartmut Gaese (Fachhochschule Köln) --------------------------------------------------------------------------------------------- Tag der öffentlichen Verteidigung: 7.5.2008 Design of Watershed Based Water Quality Monitoring The Case of Nitrate Pollution in the Aconcagua River, Chile Dissertation For the academic degree of Doctor rerum naturalium (Dr. rer. nat.) Friedrich-Schiller-University Jena Faculty of Chemistry and Earth Sciences Author: Dipl.Chem. Lars Ribbe (M.Eng) February 2008 Preface The research which led to the present dissertation has been realized between 2004 and 2007 under the umbrella of the university cooperation between the Catholic University of Valparaíso, Chile and Cologne University of Applied Sciences, Germany. Both universities provided valuable support in terms of funding and personnel to render the research possible. In addition, the support of the German Ministry of Education and Science (BMBF) is appreciated as they provided support to the project for mobility and consumables. In particular, I would like to thank Prof. Dr. Hartmut Gaese for his incessant personal and institutional support and Prof. Dr. Eduardo Salgado for the invaluable help on the Chilean side throughout the study. I am very grateful to have had Prof. Dr. Wolfgang-Albert Flügel as the main supervisor during this research and appreciated his critical and very helpful review and recommendations throughout the work leading to this thesis. Through him and through his research team at the Friedrich-Schiller-University I had the chance to become acquainted with new and fascinating aspects of integrated river basin modelling and management. In addition, there are other institutions and persons that generously supported the field work, above all the Chilean Water Service (DGA). DGA-Santiago provided the bulk of the required data on hydrology, water quality and GIS. The regional DGA in Quillota supported the sampling in the Pocochay sub-watershed. Personally, I would like to thank Mesenia Atenas, Monica Pardo, Cristian Nuñez and Francisco Riestra (Department of Water Conservation and Protection) and Ana Maria Gangas, María Angélica Alegría and Victoria Pozo (Department of Studies) for their kind support and advice. At the Catholic University of Valparaiso I thank Paula Delgado for supporting sampling and for discussing sampling design in the Pocochay stream and for organising the agricultural survey in the Pocochay sub-watershed study together with Sebastian Rivera. Finally, I would like to thank Maxime Souvignet regarding tremendous support in many technical aspects and on the revision of the text, Santiago Penedo, Rui Pedroso, and Alexandra Nauditt for the review and support in all aspects during the final phase of compiling the thesis. Content List of Tables ........................................................................................................i List of Figures ...................................................................................................... ii List of Acronyms ................................................................................................. iv Abstract .............................................................................................................. v Zusammenfassung (Summary in German) .............................................................. vi 1. Introduction.................................................................................................1 2. Background .................................................................................................3 2.1. Significance of Monitoring ....................................................................................3 2.1.1. Relation between Monitoring and the Decision Making Process................................................3 2.1.2. Definitions and Types of Monitoring.....................................................................................6 2.1.3. Conclusions......................................................................................................................8 2.2. Review of Monitoring Network Design ....................................................................8 2.2.1. Introduction .....................................................................................................................8 2.2.2. Monitoring Frequency ......................................................................................................11 2.2.3. Monitoring Locations .......................................................................................................14 2.2.4. Variability of Water Quality Parameters .............................................................................16 2.2.5. Shortcomings of Monitoring Design Methods ......................................................................17 2.3. Research Problem ............................................................................................. 18 2.4. Objectives ....................................................................................................... 19 2.5. Methodology .................................................................................................... 20 3. Nitrate Processes and Modelling.................................................................... 22 3.1. Environmental Behaviour of Nitrate ..................................................................... 22 3.1.1. Significance of Nitrate Pollution in Surface Waters...............................................................22 3.1.2. Nitrogen Pathways to Surface Waters ................................................................................23 3.1.3. Factors influencing Nitrogen Export from Irrigated Areas .....................................................25 3.1.4. Nitrogen impacts from Point Sources.................................................................................28 3.1.5. Nitrogen Processes in Surface Waters................................................................................28 3.2. Modelling Nitrate in Watersheds .......................................................................... 30 3.3. Conceptual Model to Develop Long Term Nitrate Concentrations .............................. 31 3.3.1. Nitrogen Inputs to River Reaches......................................................................................32 3.3.2. Watershed Hydrology ......................................................................................................35 4. Aconcagua Watershed Analysis ..................................................................... 39 4.1. Introduction to the Study Area............................................................................ 39 4.2. Watershed Description....................................................................................... 41 4.2.1. Location and General Description of the Watershed .............................................................41 4.2.2. Climate and Hydrology ....................................................................................................43 4.2.3. Land Use .......................................................................................................................56 4.2.4. Water Uses ....................................................................................................................62 4.2.5. Nitrogen Sources of Pollution............................................................................................68 4.2.6. Reported River Water Quality Data....................................................................................75 4.2.7. Conclusions....................................................................................................................77 5. Pocochay Sub-watershed Analysis................................................................. 78 5.1. Land and Fertilizer Use ...................................................................................... 79 5.1.2. Fertilizer Applications ......................................................................................................81 5.2. Water Quality and Discharge Measurements ......................................................... 82 5.2.1. Monitoring Points ............................................................................................................82 5.2.2. Measurement Methods.....................................................................................................82 5.2.3. Nitrogen Loads and Export Coefficients..............................................................................83 5.2.4. Interpretation of Results ..................................................................................................86 6. Modelling Nitrate Variability in the Aconcagua River ......................................... 87 6.1. Model Set up and Inputs .................................................................................... 88 6.1.1. Determine