INSTITUT FÜR HYDROLOGIE ALBERT-LUDWIGS-UNIVERSITÄT FREIBURG I.BR. Laurin Wissmeier Implementation of distributed solute transport d into the catchment model TAC and event based simulations using oxygen-18 Diplomarbeit unter Leitung von PD Dr. S. Uhlenbrook Freiburg i. Br., Januar 2005 INSTITUT FÜR HYDROLOGIE ALBERT-LUDWIGS-UNIVERSITÄT FREIBURG I.BR. Laurin Wissmeier Implementation of distributed solute transport into the catchment model TACd and event based simulations using oxygen-18 Referent: PD Dr. Stefan Uhlenbrook Koreferent: Dr. Jens Lange Diplomarbeit unter Leitung von PD Dr. S. Uhlenbrook Freiburg i. Br., Januar 2005 Contents ___________________________________________________________________ I Contents Contents ________________________________________________ I List of figures ___________________________________________ IV List of tables ____________________________________________ VI Notations ______________________________________________ VII Summary ______________________________________________ XII Zusammenfassung_______________________________________ XIV 1 Introduction __________________________________________ 1 1.1 Objective _______________________________________________ 1 1.2 State of the art ___________________________________________ 2 1.3 Procedure ______________________________________________ 6 2 PCRaster – a dynamic GIS ________________________________ 8 2.1 Concepts of PCRaster_______________________________________ 8 2.2 Conclusion of the development environment _______________________12 3 The catchment model TACd ________________________________13 3.1 Model structure___________________________________________13 3.2 Time step discretization in TACd: from hourly to daily time steps__________17 3.3 Model for potential evapotranspiration ___________________________18 3.4 Input regionalization _______________________________________19 3.4.1 Temperature _________________________________________19 3.4.2 Precipitation_________________________________________ 20 3.5 Snow routine ____________________________________________21 3.6 Interception routine_______________________________________ 24 3.7 Routine for direct stream input and urban runoff ___________________ 27 3.8 Runoff generation in zones of saturated overland flow ________________ 28 3.9 Soil routine_____________________________________________ 29 3.10 Runoff generation routine___________________________________ 32 3.10.1 Lateral flows_________________________________________ 35 3.10.2 Groundwater – surface water interaction _____________________ 36 3.11 Wave routing routine ______________________________________ 37 3.12 Evaluation model ________________________________________ 39 3.13 Initialization_____________________________________________41 3.14 Conclusion of model conceptualization __________________________ 42 4 Recent modifications of TACd _____________________________ 43 4.1 Methodology of error analysis ________________________________ 43 4.1.1 The internal water balance _________________________________ 43 4.1.2 The virtual test site ____________________________________ 46 4.2 Modification of potential evapotranspiration ______________________ 47 4.3 Modification of slope factor__________________________________ 48 4.4 Modification of snow routine_________________________________ 48 4.5 Modification of urban runoff routine ___________________________ 49 II _______________________________________________________Contents 4.6 Modification of soil routine __________________________________ 50 4.7 Modification of groundwater – surface water interaction_______________ 50 4.8 Modification of balance check for the wave routing routine _____________ 51 4.9 Modification of evaluation methods _____________________________ 51 4.10 Modification of initialization and calibration procedure _______________ 51 4.11 Conclusion of model modification ______________________________ 52 5 The model extension for solute transport _____________________ 53 5.1 Conceptualization of solute transport____________________________ 53 5.2 Units of solute transport ____________________________________ 55 5.3 Example code____________________________________________ 56 5.4 Solute input scenarios ______________________________________ 57 5.4.1 Input via precipitation___________________________________ 57 5.4.2 Input via dry deposition__________________________________ 57 5.4.3 Input via mineralization _________________________________ 57 5.4.4 Human input_________________________________________ 57 5.5 Interception routine of solute transport __________________________ 58 5.6 Solute translation within the river network ________________________ 58 5.7 Groundwater – surface water interaction of solute transport ____________ 59 5.8 Code verification _________________________________________ 60 5.8.1 Internal solute balance __________________________________ 60 5.8.2 Steady state water flow __________________________________ 62 5.8.3 Instantaneous point source input ___________________________ 62 5.8.4 Instantaneous area-wide input _____________________________ 63 5.8.5 Input of constant concentration ____________________________ 66 5.9 Conclusions on model development_____________________________ 68 6 Model applications _____________________________________ 69 6.1 Area of investigation _______________________________________ 69 6.1.1 Morphology ___________________________________________ 70 6.1.2 Climate_____________________________________________ 71 6.1.3 Hydrogeology ________________________________________ 74 6.1.4 Landuse ____________________________________________ 74 6.1.5 Hydrology ___________________________________________ 75 6.2 Methodology of oxygen-18 simulation ___________________________ 76 6.2.1 Basics______________________________________________ 76 6.2.2 Data sampling ________________________________________ 78 6.2.3 Unit conversion _______________________________________ 78 6.2.4 Evapotranspiration of 18O ________________________________ 79 6.2.5 Evaluation of 18O simulations ______________________________80 6.3 General comments on simulation uncertainties _____________________80 6.4 Initialization procedure for event-based simulations _________________80 6.4.1 Initialization of water storages _____________________________ 81 6.4.2 Initialization of solute storages _____________________________ 82 6.4.3 Discussion of initialization ________________________________ 82 Contents __________________________________________________________________III 6.5 Calibration of water fluxes __________________________________ 83 6.5.1 Results of Recalibration _________________________________ 83 6.5.2 Discussion of recalibration _______________________________ 83 6.6 Solute translation in the river network __________________________ 85 6.6.1 Results of solute translation ______________________________ 85 6.6.2 Discussion of solute translation ____________________________ 85 6.7 DS 05_02______________________________________________ 86 6.7.1 Characterization of DS 05_02 _____________________________ 86 6.7.2 Results of DS 05_02 ___________________________________ 87 6.7.3 Discussion of DS 05_02 _________________________________ 93 6.8 DS 07_03______________________________________________ 96 6.8.1 Characterization of DS 07_03 _____________________________ 96 6.8.2 Results of DS 07_03 ___________________________________ 98 6.8.3 Discussion of DS 07_03 _________________________________102 6.9 BRU 06_01 ____________________________________________105 6.9.1 Characterization of BRU 06_01 ____________________________105 6.9.2 Results of BRU 06_01 __________________________________106 6.9.3 Discussion of BRU 06_01 ________________________________ 107 6.10 Summarizing discussion of model applications_____________________108 6.11 Conclusion of model applications ______________________________ 111 7 Proposal for further model developments ____________________ 113 7.1 Kinematic solute transport within the river network _________________ 113 7.2 Retardation ____________________________________________ 113 7.3 Solute reactions__________________________________________ 113 7.4 Piston flow _____________________________________________ 114 7.5 Test of model uncertainties __________________________________ 115 7.6 Urban runoff routine ______________________________________ 115 7.7 Darcy flow in porous groundwater aquifers _______________________ 115 8 Final remarks ________________________________________ 116 References _____________________________________________ 118 Appendix ______________________________________________125 A. Parameter table ___________________________________________ 125 B. Additional graphs of simulation results ___________________________ 129 IV____________________________________________________ List of figures List of figures Figure 2.1: Level of linkage in dynamic GIS modeling languages (from van Deursen 1995) _____________________________________________________8 Figure 2.2: Spatial fluxes and time-variable cell attributes (from Roser 2001, after van Deursen 1995) ____________________________________________9 Figure 2.3: Script structure in PCRaster (from PCRaster 2004a) ________________ 10 Figure 2.4: D8-method of flow direction ________________________________ 11 Figure 3.1: Storages, fluxes and routines ________________________________ 14 Figure 3.2: Linear storage unit ______________________________________ 15 Figure 3.3: Modular structure (external models highlighted in red) ______________ 16 Figure 3.4: Conceptualization of the snow routine _________________________