® HANOI UNIVERSITY OF SCIENCE DRESDEN UNIVERSITY OF TECHNOLOGY PHAM THI BICH NGOC INVESTIGATION OF A LYSIMETER USING THE SIMULATION TOOL SiWaPro DSS AND ADAPTATION OF THIS PROGRAM TO VIETNAMESE REQUIREMENTS MASTER THESIS Supervisors: Prof. Peter Wolfgang Graeber Dipl. Rene Blankenburg Technical University Dresden Institute for Waste Management and Contaminated Site Treatment Hanoi - 2008 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com ACKNOWLEDGEMENTS Two years have passed and marked a historical pathway toward my Master degree. The two years were full of challenges, hopes, inspiration and wonderful support from many people.
I would like to thank you all for a big variety of reasons: My first greatest thanks go to my tutors Prof. Peter Wolfgang Graeber and Dipl. Rene Blankenburg for having guided, supported and accom- panied me through the process of this Master thesis. Thanks also for having greatly contributed to the thesis with your vast experience and advice.
Many thanks to Prof. Bui Duy Cam and Assc. Nguyen Thi Diem Trang for making great efforts to establish and design the training program frame for this master course and develop it, so I can have a chance to join this course. My acknowledgements go also to all teachers from Hanoi University of Sciences in Vietnam and Institute for Waste Management and Contaminated Site Treatment in Germany for giving me lots of valuable and interesting lectures and helping us to understand more clearly and have a thorough grasp of specific knowledge during this master course.
My grateful thanks to Dr. Axel Fischer, Mr. Christian and Mrs. Hoang Phan Mai for helping and supporting during my time in Dresden and Pirna, Germany.
Thanks also to Pham Hai Minh for all administrative support during the Master course time. I also would like to express my gratitude to: The Committee on Overseas Training Project, Ministry of Education and Training for having granted the scholarship that supported this Mater thesis 1 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Hanoi University of Sciences and Institute for Waste Management and Con- taminated Site Treatment (IAA) for providing all materials and equipments that I used during the course. Vietnam National University, Hanoi and Technical University Dresden and German Academic Exchange Service (DAAD) for supporting this Master training program in which I attended. Thanks to all the classmates for their nice and warm company for the encourage- ment and support.
And last but not least, special huge thanks to my family (my parents in law, my par- ents, my husband, my son and my brothers and sisters) and all my friends (especial- ly Mrs. Ha) and my relatives for thinking of me, helping me, and encouraging me in my pathway to a Master degree. I love you all. Hanoi, 10th December 2008 Pham Thi Bich Ngoc.
2 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com SUMMARY The main objective of this thesis is to use SiWaPro DSS to model and simulate the water flow process in the unsaturated zone with the available data from the lysime- ter number 302 in Juelich, Germany. The unsaturated zone is the portion of the subsurface above the ground water table. It contains air as well as water in the pores. This zone plays an important roll in many aspects of hydrology, such as infiltration, exfiltration, capillary rise, recharge, interflow, transpiration, runoff and erosion.
Interest in this zone has been increasing in recent years because the movement of water along with contaminants in this zone have been affecting the groundwater and the subsurface environment. Water flow is concerned with movement of water in unsaturated porous media. In order to handle water flow process under steady state or transient conditions in the unsaturated zone, a useful computer program is used to model and simulate this process. This program combines the simulation module SiWaPro for numerical modeling of water flow and contaminant transport in variably saturated media with additional simulation and parameter estimation tools, data sources for the simula- tion and a graphical user interface.
The computer-based decision support system SiWaPro DSS software is a program for modeling and simulating the processes as water flow, solute transport, bio de- gradation and sorption in variably saturated porous media. In SiWaPro DSS, the discretization of the modeling area is realized using finite elements with the GALERKIN method. SiWaPro DSS contains the 2D triangular mesh generator EasyMesh 1. The mesh generator allows the generation of meshes with varying element sizes and irregular mesh boundaries.
Currently, the generator allows flexible space quantization at modeling time given by the user. To validate SiWaPro DSS, the means of measurement data from a lysimeter expe- riment are used. Lysimeters are devices for measuring the characteristic properties 3 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com of the soil water balance, amounts of seepage water and their quality. In this thesis, lysimeter 302 located in Juelich, Germany is used for calibrating model.
The Juelich lysimeter 302 was established in August 2001, the monoliths were tak- en out from Munich-Neuherberg in June 2001 and the installation of the measure- ment devices occurred and the data logging started on December 10th 2001. This lysimeter is run by the Research Centre in Juelich (FZJ). This lysimeter is a large undisturbed lysimeter with 2m2 in area and 2,4m in depth including 0,8m of refer- ence material. The three suction cups are installed together with tensiometers, TDR and temperature sensors at 3-different depth layers distance from upper edge of the lysimeter in turn as 0,85m; 1,15m and 1,8m.
To model the water flow of the lysimeter in SiWaPro DSS, the finite element mesh of the lysimeter is constructed with the column of 1,6m in width and 1,6m in height (excluding 0,8m of reference material). The lower boundary condition is a first kind boundary condition that allows outflow only. A second type boundary condition is applied at the upper boundary of the column of lysimeter. It is a transient boundary condition using time – variable boundary conditions to simulate precipitation in the model.
Three soil water sampling device layers are applied as first kind boundary condition, and as the lower boundary condition, only outflow is allowed. The col- umn of the lysimeter soil is divided into 5 layers; each of the soil layers is described in its hydraulics with 11 parameters. To calibrate model, two data sets of 11 soil hydraulic and van Genuchten parame- ters with different initial pressure head and boundary condition of three suction cup layers as well as different amount of nodes and elements in the mesh are used. Be- cause the time is short – besides, one model took from 25 hours to 50 hours for run- ning; some models took much more time, then they were stopped before they finish.
So there are only 10 models were run. After getting the result from simulation of each model, the simulation result was checked and analyzed and then the data set was changed or finite element mesh of the lysimeter was adjusted or the software 4 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com was reconsidered. The simulation results that were shown in diagrams in section 4.1 are the best model, but the results still show some difference of output between si- mulation and measurement because input data which took from lysimeter station are not well documented and some soil parameters which are estimated by the person who operate the lysimeter are different from the fact. The result shows that total inflow and total outflow of lysimeter are in balance.
That means the model and fi- nite element mesh of the lysimeter is designed well. Outflow of the suction cup layer number 3 in the simulation is almost the same as measurement. Outflow of the suction cup layer number 1 and lower boundary condition in simulation are the same as measurement in the first year. But in the second year, outflow of the suction cup layer number 1 in simulation is higher than measurement; opposite to the out- flow of the lower boundary condition the simulation one is lower than measure- ment.
Outflow at the suction cup layer number 2 is different increasing by time be- tween simulation and measurement. The differences come from the data mentioned as above. The SiWaPro DSS program have been introducing to Federal Environmental Bu- reaus and Consulting Companies in Germany. These Bureaus and Companies can use this software tool primarily for leachate forecasts with respect to the German soil protection law.
In Vietnam it also can be apply similar to Germany, but it takes a bit time for Vietnamese to familiar with it. For Vietnamese to apply this software, the GUI and help system were initially translated into Vietnamese. Therefore, it can be said that SiWaPro DSS is one of the useful tools for leachate forecast. However, it should be applied for a wide variety of contaminants if the software is revised to adapt with not only all available data but also a few available data.
The lysimeter is good for calibrating the model and will be better if the data is documented well and frequency. 5 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com TABLE OF CONTENTS ACKNOWLEDGEMENTS. 3 TABLE OF CONTENTS. 8 LIST OF FIGURES.
9 LIST OF TABLES. 11 LIST OF DIAGRAMMS. FUNDAMENTALS OF SOIL HYDROLOGY .1 Definition of soil and unsaturated zone .2 Soil hydraulic parameters .3 Soil water balance .4 Soil water flow. MATERIAL AND METHODS .1 Theoretical approaches and methodology .2 Finite element method .1 General information about lysimeter .2 Juelich lysimeter station description .3 Description of the Juelich lysimeter number 302 .4 Water flow model .5 Description of the finite element mesh of the lysimeter .6 Description of software SiWaPro DSS .2 Layout and Structure .1 Graphical user interface (GUI) and Help System.
44 6 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.6 Import and Export Interfaces .3 Manual SiWaPro DSS Mesh Generator .1 Create a simple 2D mesh .2 Definition internal curves .3 Inserting a background image as construction basis .4 Boundary condition editor .7 Data sets for calibrating the model .5 Soil hydraulic parameters .2 Extension and adaptation to Vietnam requirements. DISSCUSSION AND CONCLUSIONS. 76 STATEMENT UNDER OATH. 80 Appendix 1: Precipitation using for simulation.80 Appendix 2: Brief of output of simulation for 784 days .85 Appendix 3: Data from measurement .89 Appendix 4: Data from simulation for the days equivalent with measurement days .90 7 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com ABBREVIATIONS BbodSchG German Soil Protection Law CART Classification and Regression Trees CART Classification and Regression Trees DSS Decision Support System Eq Equation FE Finite Element FZJ The Research Center in Juelich GMDH Group Method of Data Handling GSF The National Research Center for Environment and Health GUI Graphical User Interface LUA NRW The North Rhine-Westphalia State Environment Agency NIPP National Institute of Plant Protection PFT Pedotransfer Function SiWaPro Sickerwasserprognose / Leachate Forecast SKE 1 Soil water sampling device layer 1 at 0,85m distance to upper edge of the lysimeter SKE 2 Soil water sampling device layer 2 at 1,15m distance to upper edge of the lysimeter SKE 3 Soil water sampling device layer 3 at 1,80m distance to upper edge of the lysimeter SKE Saugkerzenebene / Soil water sampling device layer TDR Time domain reflectometry vGP van Genuchten Parameter 8 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com LIST OF FIGURES Figure 1: The unsaturated zone compares with the saturated zone .16 Figure 2: Division of soil fraction sizes, German (left) and American (right).17 Figure 3: Dicretization / meshing of area to be modeled.25 Figure 4: Boundary conditions and discetization of a simple model for groundwater flow (from Chris McDermott, 2003) .26 Figure 5: Boundary conditions and discretization for a simple column model .26 Figure 6: Stress applied to the top of the rock column causes deformation.27 Figure 7: Mesh in details .