The importance of alternative conceptual models for simulation of concentrations in a multi-aquifer system
Tóm tắt
Four different conceptual models based on alternative geological interpretations were formulated for a shallow 600 km2 aquifer system in Denmark comprising Quaternary deposits. Each of the four models was calibrated against groundwater heads and discharge measurements through inverse modeling. Subsequently, the transport capabilities of the four models were compared to 32 concentration measurements of environmental tracers (tritium 3H, helium-3 3He, chlorofluorocarbons CFC11, CFC12 and CFC113). The flow simulations showed only minor differences in spatial head distribution associated with alternative conceptualizations despite the complexity of the aquifer system and the significant differences in geological interpretations. The models, however, showed major differences in predictions of the age of the groundwater and environmental tracer concentrations, differences that are seen as an effect of model structure uncertainty, because no additional calibrations to these data were performed. A single conceptualization may be adequate in characterizing the natural behavior of a field system after calibration, because the calibration procedure is able to compensate for errors in the data or in the conceptual model through biased parameter values. However, once extrapolation beyond the calibration base is attempted, different conceptual model formulations result in significantly different results. Consequently, it is crucial to take model conceptual uncertainty into account when making predictions beyond the calibration base.
Tài liệu tham khảo
Abbott MB, Bathurst JC, Cunge JA, Connell PE, Rasmussen J (1986) An introduction to the European Hydrological System-Systeme Hydrologique Europeen, “SHE”: 2, structure of a physically-based, distributed modelling system. J Hydrol 87:61–77
Anderman ER, Hill MC (1999) A new multistage groundwater transport inverse method: presentation, evaluation, and implications. Water Resour Res 35:1053–1063
Anderson MP, Woessner WW (1992) Applied groundwater modeling. Academic, San Diego, CA, USA
Barlebo HC (2000) Parameter identification in groundwater modelling (inverse modelling). PhD Thesis, ISVA series paper no. 75, Technical University of Denmark, Denmark
Beckers J, Frind EO (2001) Simulating groundwater flow and runoff for the Oro Moraine aquifer system. Part II. Automated calibration and mass balance calculations. J Hydrol 243:73–90
Beven K (2002) Towards a coherent philosophy for modelling the environment. Proc R Soc Lond A Math Phys Eng Sci 458(2026):2465–2484
Bredehoeft JD (2003) From models to performance assessment: the conceptualization problem. Ground Water 41(5):571–577
Bredehoeft J (2005) The conceptualization model problem-surprise. Hydrogeol J 13(1):37–46
Carrera J, Mousavi SF, Usunoff E, Sanchez-Vila X, Galarza G (1993) A discussion on validation of hydrogeological models. Reliab Eng Syst Saf 42:201–216
Christensen S (1994) Hydrological model for the Tude: a catchment. Nord Hydrol 25:145–166
Christensen S (1997) On the strategy of estimating regional-scale transmissivity fields. Ground Water 35:131–139
Christensen S, Cooley RL (1999) Evaluation of prediction intervals for expressing uncertainties in groundwater flow model predictions. Water Resour Res 35:2627–2639
Cook PG, Bohlke JK (2000) Determining timescale for groundwater flow and solute transport. In: Cook PG, Herczeg AL (eds) Environmental tracers in subsurface hydrology: 1–30. Kluwer, Dordrecht, Holland
Cook PG, Solomon DK, Plummer LN, Busenberg E, Schiff SL (1995) Chlorofluorocarbons as tracers of groundwater transport processes in a shallow, silty sand aquifer. Water Resour Res 31:425–434
Ernstsen V, Jacobsen OS, Elsgaard L, Fomsgaard I, Vinther FP (2000) Geokemi, omsætning og sorption af pesticider i den umættede zone [Geochemistry, reduction and sorption of pesticides in the vadose zone]. Miljøforskning 42(1):10–13
Fogg GE (1986) Groundwater-flow and sand body interconnectedness in a thick, multiple-aquifer system. Water Resour Res 22:679–694
GEUS (2002) Grundvandsovervågningsboringers egnethed til analyse [Suitability of groundwater monitoring wells in analysis]. Geological Survey of Denmark and Greenland, GEUS, Copenhagen, Denmark
Gravesen P, Klint KES, Jacobsen OS, Harrar WG, Fleding G, Jørgensen P, Fomsgaard I, Spliid NH (2000) Transport af vand og pesticider i opsprækket moræneler [Transport of water and pesticides in fractured clayey till]. In: Nielsen HØ (ed) Miljøforskning 42(1):6–9
Hansen S (1950) Ekskursion til Slagelse-Korsoer-egnen [Excursion to the Slagelse-Korsoer area]. Bull Geol Soc Den 11:603–607
Harrar WG, Sonnenborg TO, Henriksen HJ (2003) Capture zone, travel time, and solute-transport predictions using inverse modeling and different geological models. Hydrogeol J 11:536–548
Henriksen HJ, Troldborg L, Knudby CJ, Dahl M, Nygaard P, Jakobsen PR, Rasmussen P (1998) National water resources model: Zealand, Lolland, Falster and Mon (in Danish). Geological Survey of Denmark and Greenland Report 1998/109. GEUS, Copenhagen, Denmark
Henriksen HJ, Troldborg L, Nygaard P, Sonnenborg TO, Refsgaard JC, Madsen B (2003) Methodology for construction, calibration and validation of a national hydrological model for Denmark. J Hydrol 280:52–71
Hojberg AL, Refsgaard JC (2005) Model uncertainty: parameter uncertainty versus conceptual models. Water Sci Technol 52(6):177–186
Houmark-Nielsen M (1987) Pleistocene stratigraphy and glacial history of the central part of Denmark. Bull Geol Soc Den 36:1–189
Jakobsen PR (1996) Distribution and intensity of glaciotectonic deformation in Denmark. Bull Geol Soc Den 42(2):175–185
Klint KES, Gravesen P (1999) Fractures and biopores in Weichselian clayey till aquitards at Flakkebjerg, Denmark. Nord Hydrol 30:267–284
LaBolle EM, Fogg GE, Tompson AFB (1996) Random-walk simulation of transport in heterogeneous porous media: local mass-conservation problem and implementation methods. Water Resour Res 32:583–593
Martin PJ, Frind EO (1998) Modeling a complex multi-aquifer system: the Waterloo Moraine. Ground Water 36:679–690
Neuman SP, Wierenga PJ (2003) A comprehensive strategy of hydrogeologic modeling and uncertainty analysis for nuclear facilities and sites. NUREG/CR-6805, University of Arizona, USA. Available online. http://www.nrc.gov/reading-rm/doc-collections/nuregs/contract/cr6805/. Cited 5 May 2006
Poeter EP, Hill MC (1997) Inverse models: a necessary next step in groundwater modeling. Ground Water 35:250–260
Poeter EP, Hill MC (1998) Documentation of UCODE, a computer code for universal inverse modeling. Water-Resources Investigation Report 98-4080, USGS, Denver, Colorado
Pollock DW (1988) Semianalytical computation of path lines for finite-difference models. Ground Water 26(6):743–750
Refsgaard JC, Storm B (1995) MIKE SHE. In: Singh VP (ed) Computer models of watershed hydrology. Water Resources Publications, Highlands Ranch, CO, USA, pp 809–846
Samper J, Carrera J, Galarza G, Medina A (1990) Application of an automatic calibration technique to modelling an alluvial aquifer. IAHS-AISH Publ no. 195, IAHS, Wallingford, Oxfordshire, UK, pp 87–95
Sonnenborg TO, Engesgaard P, Rosbjerg D (1996) Contaminant transport at a waste residue deposit. 1. Inverse flow and nonreactive transport modeling. Water Resour Res 32:925–938
Toth J (1999) Groundwater as a geologic agent: an overview of the causes, processes, and manifestations. Hydrogeol J 7:1–14
Troldborg L (2004) The influence of conceptual geological models on the simulation of flow and transport in Quaternary aquifer systems, PhD Thesis, Geological Survey of Denmark and Greenland Report 2004/107, GEUS, Copenhagen, Denmark
Tsai FTC, Sun NZ, Yeh WWG (2003) A combinatorial optimization scheme for parameter structure identification in ground water modeling. Ground Water 41:156–169
Weissmann GS, Zhang Y, LaBolle EM, Fogg GE (2002) Dispersion of groundwater age in an alluvial aquifer system. Water Resour Res 38(16):1–13
Zijl W (1999) Scale aspects of groundwater flow and transport systems. Hydrogeol J 7:139–150
Zyvoloski G, Kwicklis E, Eddebbarh AA, Arnold B, Faunt C, Robinson BA (2003) The site-scale saturated zone flow model for Yucca Mountain: calibration of different conceptual models and their impact on flow paths. J Contam Hydrol 62–63:731–750