<?xml version="1.0" encoding="utf-8" standalone="no"?>
<!DOCTYPE article SYSTEM "http://www.hydrol-earth-syst-sci.net/inc/hess/copernicus.dtd">
<article language="en">
	<journal>
		<journal_title>Hydrology and Earth System Sciences</journal_title>
		<journal_url>www.hydrol-earth-syst-sci.net</journal_url>
		<issn>1027-5606</issn>
		<eissn>1607-7938</eissn>
		<volume_number>11</volume_number>
		<issue_number>4</issue_number>
		<publication_year>2007</publication_year>
	</journal>
	<doi>10.5194/hess-11-1249-2007</doi>
	<article_url>http://www.hydrol-earth-syst-sci.net/11/1249/2007/</article_url>
	<abstract_html>http://www.hydrol-earth-syst-sci.net/11/1249/2007/hess-11-1249-2007.html</abstract_html>
	<fulltext_pdf>http://www.hydrol-earth-syst-sci.net/11/1249/2007/hess-11-1249-2007.pdf</fulltext_pdf>
	<start_page>1249</start_page>
	<end_page>1266</end_page>
	<publication_date>2007-05-03</publication_date>
	<article_title content_type="html">Uncertainty, sensitivity analysis and the role of data based mechanistic modeling in hydrology</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>M. Ratto</name>
		</author>
		<author numeration="2" affiliations="2,3">
			<name>P. C. Young</name>
		</author>
		<author numeration="3" affiliations="2">
			<name>R. Romanowicz</name>
		</author>
		<author numeration="4" affiliations="2,4">
			<name>F. Pappenberger</name>
		</author>
		<author numeration="5" affiliations="1">
			<name>A. Saltelli</name>
		</author>
		<author numeration="6" affiliations="1">
			<name>A. Pagano</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Joint Research Centre, European Commission, Ispra, Italy</affiliation>
		<affiliation numeration="2" content_type="html">Centre for Research on Environmental Systems and Statistic, Lancaster University, Lancaster, UK</affiliation>
		<affiliation numeration="3" content_type="html">Centre for Resource and Environmental Studies, Australian National University, Canberra, Australia</affiliation>
		<affiliation numeration="4" content_type="html">European Centre for Medium-Range Weather Forecasts, Reading, UK</affiliation>
	</affiliations>
	<abstract content_type="html">In this paper, we discuss a joint approach to calibration and
uncertainty estimation for hydrologic systems that combines a
top-down, data-based mechanistic (DBM) modelling methodology; and
a bottom-up, reductionist modelling methodology. The combined
approach is applied to the modelling of the River Hodder catchment
in North-West England. The top-down DBM model provides a well identified,
statistically sound yet physically meaningful description of the
rainfall-flow data, revealing important characteristics of the
catchment-scale response, such as the nature of the effective
rainfall nonlinearity and the partitioning of the effective
rainfall into different flow pathways. These characteristics are
defined inductively from the data without prior assumptions about
the model structure, other than it is within the generic class of
nonlinear differential-delay equations. The bottom-up modelling is
developed using the TOPMODEL, whose structure is assumed a
priori and is evaluated by global sensitivity analysis (GSA) in
order to specify the most sensitive and important parameters. The
subsequent exercises in calibration and validation, performed with
Generalized Likelihood Uncertainty Estimation (GLUE), are carried
out in the light of the GSA and DBM analyses. This allows for the
&lt;i&gt;pre-calibration&lt;/i&gt; of the the priors used for GLUE, in order to
eliminate dynamical features of the TOPMODEL that have little
effect on the model output and would be rejected at the structure
identification phase of the DBM modelling analysis. In this way,
the elements of meaningful subjectivity in the GLUE approach,
which allow the modeler to interact in the modelling process by
constraining the model to have a specific form prior to
calibration, are combined with other more objective, data-based
benchmarks for the final uncertainty estimation. GSA plays a major
role in building a bridge between the hypothetico-deductive
(bottom-up) and inductive (top-down) approaches and helps to
improve the calibration of mechanistic hydrological models, making
their properties more transparent. It also helps to highlight
possible mis-specification problems, if these are identified. The
results of the exercise show that the two modelling methodologies
have good synergy; combining well to produce a complete joint
modelling approach that has the kinds of checks-and-balances
required in practical data-based modelling of rainfall-flow
systems. Such a combined approach also produces models that are
suitable for different kinds of application. As such, the DBM
model considered in the paper is developed specifically as a
vehicle for flow and flood forecasting (although the generality of
DBM modelling means that a simulation version of the model could
be developed if required); while TOPMODEL, suitably calibrated
(and perhaps modified) in the light of the DBM and GSA results,
immediately provides a simulation model with a variety of
potential applications, in areas such as catchment management and
planning.</abstract>
	<references>
		<reference numeration="1" content_type="text"> Campolongo, F., Cariboni, J., and Saltelli, A.: An effective screening design for sensitivity analysis of large models, Environ. Modell. Software, 22, 1509&amp;ndash;1518, 2007.  </reference>
		<reference numeration="2" content_type="text"> Beven, K. J. and Binley, A.: The future of distributed models: model calibration and uncertainty prediction, Hydrol. Processes, 6, 279&amp;ndash;298, 1992. </reference>
		<reference numeration="3" content_type="text"> Beven, K. J. and Kirkby, M.J.: A physically based variable contributing area model of basin hydrology, Hydrol. Sci. Bull., 24, 43&amp;ndash;69, 1979. </reference>
		<reference numeration="4" content_type="text"> Hall, J. W., Tarantola, S., Bates, P. D., and Horritt, M. S.: Distributed sensitivity analysis of flood inundation model calibration, J. Hydraul. Eng.-Asce., 131, 117&amp;ndash;126, 2005. </reference>
		<reference numeration="5" content_type="text"> Hornberger G. M. and Spear R. C.: An approach to the preliminary analysis of environmental systems, J. Environ. Manage., 7, 7&amp;ndash;18, 1981. </reference>
		<reference numeration="6" content_type="text"> Jakeman, A. J., Littlewood, I. G., and Whitehead, P. G.: Computation of the instantaneous unit hydrograph and identifiable component flows with application to two small upland catchments, J. Hydrol., 117, 275&amp;ndash;300, 1990. </reference>
		<reference numeration="7" content_type="text"> Li, G., Wang, S. W., and Rabitz, H.: Practical approaches to construct RS-HDMR component functions, J. Phys. Chem., 106, 8721&amp;ndash;8733, 2002. </reference>
		<reference numeration="8" content_type="text"> Li, G., Hu, J., Wang, S.-W., Georgopoulos, P. G., Schoendorf, J., and Rabitz, H.: Random Sampling-High Dimensional Model Representation (RS-HDMR) and Orthogonality of Its Different Order Component Functions, J. Phys. Chem. A, 110, 2474&amp;ndash;2485, 2006. </reference>
		<reference numeration="9" content_type="text"> Moradkhani, H., Sorooshian, S., Gupta, H. V., and Houser, P. R.: Dual state-parameter estimation of hydrological models using ensemble Kalman filter, Adv. Water Resour., 28, 135&amp;ndash;147, 2005. </reference>
		<reference numeration="10" content_type="text"> Morris, M. D.: Factorial sampling plans for preliminary computational experiments, Technometrics, 33, 161&amp;ndash;174, 1991. </reference>
		<reference numeration="11" content_type="text"> Oakley, J. E. and O&apos;Hagan, A.: Probabilistic sensitivity analysis of complex models: a Bayesian approach, J. R. Statist. Soc. B, 66, 751&amp;ndash;769, 2004. </reference>
		<reference numeration="12" content_type="text"> Pappenberger, F. and Beven, K J.: Functional Classification and Evaluation of Hydrographs based on Multicomponent Mapping, International Journal of River Basin Management, 2(2), 1&amp;ndash;9, 2004. </reference>
		<reference numeration="13" content_type="text"> Pappenberger, F. and Beven, K J.: Ignorance is bliss: Or seven reasons not to use uncertainty analysis, Water Resour. Res., 42, 5302, doi:10.1029/2005WR004820, 2006. </reference>
		<reference numeration="14" content_type="text"> Pappenberger, F., Beven, K. J., Horritt, M., and Blazkova, S.: Uncertainty in the calibration of effective roughness parameters in HEC-RAS using inundation and downstream level observations, J. Hydrol., 302(1&amp;ndash;4), 46&amp;ndash;69, 2005. </reference>
		<reference numeration="15" content_type="text"> Pappenberger, F., Harvey, H., Beven, K., Hall, J., and Meadowcroft, I.: Decision tree for choosing an uncertainty analysis methodology: a wiki experiment, Hydrol. Processes, 20, 3793&amp;ndash;3798, 2006a. </reference>
		<reference numeration="16" content_type="text"> Pappenberger, F., Iorgulescu, I., and Beven, K. J.: Sensitivity Analysis based on regional splits and regression trees (SARS-RT), Environmental Modelling and Software, 21(7), 976&amp;ndash;990, 2006b. </reference>
		<reference numeration="17" content_type="text"> Pappenberger, F., Matgen, P., Beven, K. J., Henry, J.-B., Pfister, L., and de Fraipont, P.: Influence of uncertain boundary conditions and model structure on flood inundation predictions, Adv. Water Resour., 29, 1430&amp;ndash;1449, 2006c. </reference>
		<reference numeration="18" content_type="text"> Pappenberger, F., Frodsham, K. Beven, K. ,Romanowicz, R., and Matgen, P.: Fuzzy set approach to calibrating distributed flood inundation models using remote sensing observations, Hydrol. Earth Syst. Sci., 11, 739-752, 2007. </reference>
		<reference numeration="19" content_type="text"> Ratto, M., Tarantola, S., and Saltelli, A.: Sensitivity analysis in model calibration: GSA-GLUE approach, Computer Physics Communication, 136, 212&amp;ndash;224, 2001. </reference>
		<reference numeration="20" content_type="text"> Ratto, M., Tarantola, S., Saltelli, A., and Young, P. C.: Accelerated estimation of sensitivity indices using State Dependent Parameter models, in: Proc. 4th Int. Conf on Sensitivity Analysis of Model Output (SAMO 2004), Santa Fe, New Mexico, 8&amp;ndash;11 March, edited by: Hanson, K. M. and Hemez, F. M., electronic proceedings, 61&amp;ndash;70, 2004. </reference>
		<reference numeration="21" content_type="text"> Ratto, M., Saltelli, A., Tarantola, S., and Young, P. C.: Improved and accelerated sensitivity analysis using State Dependent Parameter models, EUR Technical Report, Joint Research Centre of the European Commission, 2006.  </reference>
		<reference numeration="22" content_type="text"> Romanowicz, R. J.: A MATLAB implementation of TOPMODEL, Hydrol. Processes, 11, 1115&amp;ndash;1129, 1997. </reference>
		<reference numeration="23" content_type="text"> Romanowicz, R. J. and Macdonald, R.: Modelling uncertainty and variability In environmental systems, Acta. Geophys. Pol., 53, 401&amp;ndash;417, 2005. </reference>
		<reference numeration="24" content_type="text"> Romanowicz, R., Beven, K. J., and Young, P. C.: Assessing the risk of flooding in real time, Proc. ACTIF Conference on Quantification, reduction and dissemination of uncertainty in flood forecasting, Delft, Netherlands, http://www.actif-ec.net/Workshop2/papers/ACTIF_S1_06.pdf, reviewed online publication, 2004. </reference>
		<reference numeration="25" content_type="text"> Romanowicz, R. J. and Beven, K.: Comments on Generalised Likelihood Uncertainty Estimation, Reliability Engineering and System Safety, 91, 1315&amp;ndash;1321, 2006. </reference>
		<reference numeration="26" content_type="text"> Romanowicz, R., Young, P.C., and Beven, K. J.: Data assimilation and adaptive forecasting of water levels in the river Severn catchment, UK, Water Resour. Res., W06407, doi:10.1029/WR004373, 2006. </reference>
		<reference numeration="27" content_type="text"> Saltelli, A., Chan, K., and Scott, M. (Eds.): Sensitivity Analysis, John Wiley and Sons publishers, Probability and Statistics series, 2000. </reference>
		<reference numeration="28" content_type="text"> Saltelli, A., Ratto, M., Tarantola, S., and Campolongo, F.: Sensitivity analysis for chemical models, Chem. Rev., 105, 2811&amp;ndash;2828, 2005. </reference>
		<reference numeration="29" content_type="text"> Saltelli, A. and Tarantola, S.: On the relative importance of input factors in mathematical models: safety assessment for nuclear waste disposal, J. Am. Stat. Assoc., 97(459), 702&amp;ndash;709, 2002. </reference>
		<reference numeration="30" content_type="text"> Saltelli, A., Tarantola, S., Campolongo, F., and Ratto, M.: Sensitivity Analysis in Practice: A Guide to Assessing Scientific Models, John Wiley and Sons, 2004. </reference>
		<reference numeration="31" content_type="text"> Sobol&apos;, I. M.: Sensitivity estimates for nonlinear mathematical models, Matematicheskoe Modelirovanie, 2, 112&amp;ndash;118, 1990 (in Russian), [Transl. Sensitivity analysis for non-linear mathematical models. Mathematical Modelling &amp; Computational Experiment, 1, 407&amp;ndash;414, 1993.] </reference>
		<reference numeration="32" content_type="text"> Sobol&apos; I. M., Turchaninov, V. I., Levitan, Y. L., and Shukhman, B. V.: Quasirandom sequence generators, Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, 1992. </reference>
		<reference numeration="33" content_type="text"> Spear, R. C., Grieb, T. M., and Shang, N.: Factor Uncertainty and Interaction in Complex Environmental Models, Water Resour. Res., 30, 3159&amp;ndash;3169, 1994. </reference>
		<reference numeration="34" content_type="text"> Tang, Y., Reed, P., Wagener, T., and van Werkhoven, K.: Comparing sensitivity analysis methods to advance lumped watershed model identification and evaluation, Hydrol. Earth Syst. Sci., 11, 793&amp;ndash;817, 2007. </reference>
		<reference numeration="35" content_type="text"> Vrugt, J. A., Diks, C. G. H., Gupta, H. V., Bouten, W., and Verstraten, J. M.; Improved treatment of uncertainty in hydrologic modeling: combining the strengths of global optimization and data assimilation, Water Resour. Res., 41, W01017, doi:10.1029/2004WR003059 2005. </reference>
		<reference numeration="36" content_type="text"> Wheater, H. S., Jakeman, A. J., and Beven, K. J.: Progress and directions in rainfall-run-off modelling, in: Modelling Change in Environmental Systems, edited by: Jakeman, A. J., Beck, M. B. and McAleer, M. J., Chapter 5, Wiley: Chichester, 1993. </reference>
		<reference numeration="37" content_type="text"> Whitehead, P. G. and Young, P. C.: A dynamic stochastic model for water quality in part of the Bedford-Ouse river system, in: Modeling and Simulation of Water Resource Systems, edited by: Vansteenkiste, G., North Holland, Amsterdam, p 417&amp;ndash;430, 1975. </reference>
		<reference numeration="38" content_type="text"> Young, P. C.: Recursive Approaches to Time-Series Analysis, Bull. Inst. Maths Appl., 10, 209&amp;ndash;224, 1974. </reference>
		<reference numeration="39" content_type="text"> Young, P. C.: Recursive Estimation and Time-Series Analysis, Springer-Verlag, Berlin, 1984. </reference>
		<reference numeration="40" content_type="text"> Young, P. C.: Data-based mechanistic modelling of environmental, ecological, economic and engineering systems, Environ. Modell. Software, 13, 105&amp;ndash;122, 1998. </reference>
		<reference numeration="41" content_type="text"> Young, P. C.: Data-based mechanistic modelling, generalised sensitivity and dominant mode analysis, Computer Physics Communication, 117, 113&amp;ndash;129, 1999. </reference>
		<reference numeration="42" content_type="text"> Young, P. C.: Data-based mechanistic modelling and validation of rainfall-flow processes, in: Model Validation: Perspectives in Hydrological Science, edited by: Anderson, M. G. and Bates, P. D. John Wiley, Chichester, 117&amp;ndash;161, 2001. </reference>
		<reference numeration="43" content_type="text"> Young, P. C.: Advances in real-time flood forecasting, Philosophical Trans. Royal Society, Phys. Eng. Sci., 360, 1433&amp;ndash;1450, 2002. </reference>
		<reference numeration="44" content_type="text"> Young, P. C.: Top-down and data-based mechanistic modelling of rainfall-flow dynamics at the catchment scale, Hydrol. Processes, 17, 2195&amp;ndash;2217, 2003. </reference>
		<reference numeration="45" content_type="text"> Young, P. C.: Rainfall-runoff modeling: Transfer Function models, in: Encyclopedia of Hydrological Sciences, edited by: Anderson, M. G. John Wiley, Hoboken, N. J., Vol 3, part~II, 1985&amp;ndash;2000, 2005. </reference>
		<reference numeration="46" content_type="text"> Young, P. C.: Data-based mechanistic modelling and river flow forecasting, in: Proceedings 14th International Federation on Automatic Control (IFAC) Symposium on System Identification, Newcastle, NSW, 756&amp;ndash;761, 2006. </reference>
		<reference numeration="47" content_type="text"> Young, P. C., Romanowicz, R., and Beven, K. J.: Data-based mechanistic modelling and real-time adaptive flood forecasting, in: Proceedings of Institution of Civil Engineers and British Hydrological Society Workshop on Real-Time Flood Forecasting: Developments and Opportunities, City Conference Centre, London, 14 November 2006. </reference>
		<reference numeration="48" content_type="text"> Young, P. C., Spear, R. C., and Hornberger, G. M.: Modeling Badly Defined Systems: Some Further Thoughts, Proceedings SIMSIG Conference, SIMSIG, Canberra, 1978. </reference>
		<reference numeration="49" content_type="text"> Young, P. C., Parkinson S. D., and Lees M.: Simplicity out of complexity: Occam&apos;s razor revisited, J. Appl. Stat., 23, 165&amp;ndash;210, 1996.  </reference>
	</references>
</article>

