Ungaged catchment hydrology at Irstea
Concept Note
1. Context
While the production of a model that would not require any calibration can be seen as the
long-term objective of hydrological science, hydrologists worldwide are still far from having
reached it. Most of the currently used hydrological models, regardless of their structure and
their underlying assumptions are still data-driven, and require some sort of calibration with
observed flow data in order to realistically reproduce the hydrological behaviour of a
particular catchment.
As a logical consequence, major difficulties are encountered when applying these models to
ungaged catchments for which no flow data are available and no calibration is possible.
Hydrologists have been attempting to develop strategies to estimate the parameters of their
models without calibration since the 1970s (see e.g. James, 1972; Magette et al., 1976). The
term regionalization takes its roots in the process of regime classification and catchment
grouping (see e.g. Pardé, 1933; Gottschalk et al., 1979) and was then extended in the rainfallrunoff modeling context to the transfer of parameters from neighboring gaged catchments
(also named donor catchments) to the ungaged catchments. Nowadays, the concept of
regionalization applies to all those methods aimed at estimating model parameter values on
any ungaged catchment.
Over the years, a number of techniques have been tested for regionalization, based either on
some notion of “physical similarity”, of “spatial proximity” or of both (see e.g. Nathan and
McMahon, 1990; Burn and Boorman, 1993; Merz and Blöschl, 2004; McIntyre et al., 2005;
Parajka et al. 2005; Bárdossy, A., 2007). One should also mention the continuous work on
physically-based distributed hydrological models, which do not rely on calibration for
parameter specification (e.g., Anquetin et al., 2010; Braud et al., 2010; Rozalis et al., 2010).
2. Past achievements at Irstea
Over the last years, Irstea's ungaged catchment related research has mainly focused on:

Rainfall-runoff models, which represent a key tool for contemporary flow forecasting,
flood design and for water-management applications;

Reference flow mapping, from extreme floods to median flows and to low flows;

Prediction of flow duration curves.
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A variety of original solutions have been developed to address the issue of ungaged basins,
including:

Making and exhaustive use of large datasets to help assess methods and evaluate their
uncertainties;

Developing approaches to blend physical similarity and geographical proximity;

Reference flow mapping;

Using of point gagings to complement regional information;

Development of modeling strategies and specification of model parameters relying on
existing data sets (topography, land use, soil data base).
Let us also mention here the work pursued on another branch of modeling, namely distributed
hydrological models, using flexible modeling platforms. Models of various complexities
requiring no calibration are developed to address the change of scale problem in hydrological
processes representation
3. Remaining challenges for ungaged catchment modelling
The fact that the international decade on the Prediction in Ungaged Basins comes to an end in
2013 does not mean that all scientific issues have been solved in that domain. Based on our
experience, we have identified seven challenges which are still awaiting a proper solution:

Challenge #1 – Obtaining new hydrologically-relevant catchment descriptors
Ungaged catchment related studies have shown that most of the standard catchment
descriptors have a poor explanatory power (in terms of explaining hydrological behavior). We
need integrated (adimensional?) descriptors which convey quantitative information on (i)
heterogeneity, (ii) connectivity & spatial organization, (iii) underground characteristics and
temporal variability of hydrometeorological processes.

Challenge #2 – Physical similarity and spatial proximity
It is a fact that some of the dominant physical processes are just unobservable. Since these
'hidden processes’ have some spatial coherence, regionalization methods based on spatial
proximity bring most of the time additional information on ungaged catchments. What still
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remains to be done is a real synthesis of approaches using physical similarity and spatial
proximity in regionalization (see e.g. Gottschalk et al., 2011a,b; Oudin et al., 2008)

Challenge #3 – sorting the wheat from the chaff
When it comes to regionalization, most of the difficulty consists in transferring the 'right'
hydrological information (from donor catchments to the ungaged catchments). All donors are
not beneficial to regionalization, some 'outliers' can even be disinformative. We need to
develop new methods for identifying those ‘regional outliers’ (see e.g. Boldetti et al., 2010).

Challenge #4 – Evaluation of regionalization approaches
We still need to agree upon a common evaluation framework (procedure, criteria, etc.) to
assess the relative value of alternative methods. To this aim, we need (i) a large catchment
dataset, to draw robust conclusions (see e.g. Andréassian et al., 2006), (ii) a varied catchment
dataset, with the largest possible diversity in hydrological situations, (iii) methods which
allow us to test the robustness of the regionalization approach (see e.g. Oudin et al., 2008;
Andréassian et al., 2009).

Challenge #5 – we need to keep improving our models while taking into account
ungaged catchment constraints
Hydrological modeling is in constant progress. What we need to do is to account for the
constraints of regionalisation while continuing to develop our models.

Challenge #6 – we need to include point streamflow measurements where
available
If man is able to send satellites around earth to observe it, and derive ungaged catchmentrelevant information from these images, he is also able to send a gauging team to collect point
streamflow measurements! We need to keep improving our methods to merge regionalization
approaches and use of point measurements (see e.g. Rojas Serna et al., 2006; Sauquet and
Catalogne, 2011).

Challenge #7 – Improve hydrological processes description using top-down and
bottom-up approaches as well as the synergy between observations and modeling
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We need to address the change of scale problem using both new observations and new
modeling approaches, using as much as possible the information which can be derived from
data (signatures of hydrological behavior).
4. Literature cited
Anquetin, S., Braud, I., Vannier, O., Viallet, P., Boudevillain, B., Creutin, J.-D., Manus, C.,
2010. Sensitivity of the hydrological response to the variability of rainfall fields and
soils for the Gard 2002 flash-flood event. Journal of Hydrology, 394(1-2): 134-147.
Bárdossy, A., 2007. Calibration of hydrological model parameters for ungauged catchments.
Hydrology and Earth System Sciences, 11: 703-710.
Braud, I., Roux, H., Anquetin, S., Maubourguet, M.-M., Manus, C., Viallet, P., Dartus, D.,
2010. The use of distributed hydrological models for the Gard 2002 flash flood
event: Analysis of associated hydrological processes. Journal of Hydrology, 394(12): 162-181.
Burn, D.H. and Boorman, D.B., 1993. Estimation of hydrological parameters at ungauged
catchments. Journal of Hydrology, 143: 429-454.
Gottschalk, L., Jensen, J.L., Lundquist, D., Solantie, R. and Tollan, A., 1979. Hydrologic
regions in the Nordic countries. Nordic Hydrology, 10: 273-286.
James, L.D., 1972. Hydrologic modeling, parameter estimation, and watershed characteristics.
Journal of Hydrology, 17: 283-307.
Magette, W.L., Shanholtz, V.O. and Carr, J.C., 1976. Estimating selected parameters for the
Kentucky watershed model from watershed characteristics. Water Resources
Research, 12(3): 472-476.
McIntyre, N., Lee, H., Wheater, H., Young, A. and Wagener, T., 2005. Ensemble predictions
of runoff in ungauged catchments. Water Resources Research, 41(12).
Merz, R. and Blöschl, G., 2004. Regionalisation of catchment model parameters. Journal of
Hydrology, 287(1-4): 95-123.
Nathan, R.J. and McMahon, T.A., 1990. Identification of homogeneous regions for the
purposes of regionalisation. Journal of Hydrology, 121: 217-238.
Parajka, J., Merz, R. and Blöschl, G., 2005. A comparison of regionalisation methods for
catchment model parameters. Hydrology and Earth System Sciences, 9: 157-171.
Pardé, M., 1933. Fleuves et Rivières, Paris, 224 pp.
Rozalis, S., Morin, E., Yair, Y., Price, C., 2010. Flash flood prediction using an uncalibrated
hydrological model and radar rainfall data in a Mediterranean watershed under
changing hydrological conditions. Journal of Hydrology, 394(1-2): 245-255.
5. References of the Irstea research teams
1. Andréassian, V., Hall, A., Chahinian, N. & Schaake, J. 2006. Introduction and Synthesis:
Why should hydrologists work on a large number of basin data sets? IAHS
Publication n°307, pp. 1-5.
2. Andréassian, V., Lerat, J., Le Moine, N., Perrin, C., 2012. Neighbors: Nature's own
hydrological
models.
Journal
of
Hydrology,
414-415:
49-58,
doi:10.1016/j.jhydrol.2011.10.007.
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3. Andréassian, V., Perrin, C., Berthet, L., Le Moine, N., Lerat, J., Loumagne, C., Oudin, L.,
Mathevet, T., Ramos, M.H., Valéry, A., 2009. Crash tests for a standardized
evaluation of hydrological models. Hydrol. Earth. Syst. Sci. 13, 1757-1764,
doi:10.5194/hess-13-1757-2009.
4. Anquetin, S., Braud, I., Vannier, O., Viallet, P., Boudevillain B., Creutin, J.D., Manus, C.,
2010. Sensitivity of the hydrological response to rainfall fields estimation and soil
variabilities in the context of flash floods, Journal of Hydrology, Flash Floods
special issue, 394, 134-147, DOI: 10.1016/j.jhydrol.2010.07.002.
5. Arnaud, P., Lavabre, J., Sol, B., Desouche, C. - 2008. Regionalization of an hourly rainfall
model in French territory for rainfall risk estimation. Hydrological Sciences Journal,
vol. 53, n° 1, p. 34-47 27 p.
6. Boldetti, G., Riffard, M., Andréassian, V. and Oudin, L. 2010. Data-set cleansing
practices and hydrological regionalization: is there any valuable information among
outliers?
Hydrological
Sciences
Journal,
55(6):
941-951.
DOI:
10.1080/02626667.2010.505171
7. Branger, F., Braud, I., Debionne, S., Viallet, P., Dehotin, J., Hénine, H., Nédélec, Y.,
Anquetin, S., 2010. Towards multi-scale integrated hydrological models using the
LIQUID framework. Overview of the concepts and first application examples,
Environmental
Modeling
&
Software,
25,
1672-1681,
doi:10.1016/j.envsoft.2010.06.005.
8. Braud, I., Roux, H., Anquetin, S., Maubourguet, M.M., Manus, C., Viallet, P., Dartus D.,
2010: The use of distributed hydrological models for the Gard 2002 Flash-Flood
event. Analysis of associated hydrological processes, Journal of Hydrology, 394,
162-181, DOI:10.1016/j.jhydrol.2010.03.033.
9. Dehotin, J., Braud, I., 2008. Which spatial discretization for distributed hydrological
models? Proposition of a methodology and illustration for medium to large scale
catchments, Hydrology and Earth System Sciences, 12, 769-796.
10. Engeland, K., Braud, I., Gottschalk, L., Leblois, E., 2006. Multi-objective regional
modelling, J. Hydrology, 327 (3-4), 339-351.
11. Folton, N. and J. Lavabre. 2006. Regionalization of a monthly rainfall–runoff model for
the southern half of France based on a sample of 880 gauged catchments. IAHS
Publication n°307, pp. 264-277.
12. Gottschalk L., Krasovskaia I., Leblois E. & Sauquet E. 2006. Mapping mean and variance
of runoff in a river basin. Hydrol. Earth Syst. Sci., 10, 469-484.
13. Gottschalk, L., Leblois, E., Skoien, J.O. - 2011. Correlation and covariance of runoff
revisited. Journal of Hydrology, vol. 398, n° 1-2, p. 76-90
14. Gottschalk, L., Leblois, E., Skoien, J.O. - 2011. Distance measures for hydrological data
having a support. Journal of Hydrology, vol. 402, n° 3-4, p. 415-421
15. Javelle, P., Fouchier, C., Arnaud, P., Lavabre, J. - 2010. Flash flood warning at ungauged
locations using radar rainfall and antecedent soil moisture estimations. Journal of
Hydrology, vol. 394, p. 267-274
16. Jankowfsky, S., Branger, F., Braud, I., Gironas, J., Rodriguez, F., 2012. Comparison of
catchment and network delineation approaches in complex suburban environments.
Application to the Chaudanne catchment, France, Hydrological Processes, in press,
doi: 10.1002/hyp.9506
17. Laaha G., Sauquet E., Hisdal H., Kroll C.N., van Lanen, H.A.J, Tallaksen L.M. & Woods
R. (2010). FRIEND's contribution to the PUB Benchmark Assessment Report on
low flow estimation. AISH Publ. 340, 54-60.
18. Manus, C., Anquetin, S., Braud, I., Vandervaere, J.P., Viallet, P., Creutin, J.D., Gaume,
E., 2009. A modelling approach to assess the hydrological response of small
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Mediterranean catchments to the variability of soil characteristics in a context of
extreme events, Hydrology and Earth System Sciences, 13, 79-97.
19. Oudin, L., A. Kay, V. Andréassian, and C. Perrin. 2010. Are seemingly physically similar
catchments truly hydrologically similar? Water Resources Research, 46, W11558,
doi:10.1029/2009WR008887
20. Oudin, L., Andréassian, V., Lerat, J., Michel, C. 2008. Has land cover a significant impact
on mean annual streamflow? An international assessment using 1508 catchments.
Journal of Hydrology, 357(3-4), 303-316. DOI: 10.1016/j.jhydrol.2008.05.021
21. Oudin, L., Andréassian, V., Loumagne, C. & Michel , C. 2006. How informative is landcover for the regionalization of the GR4J rainfall-runoff model? IAHS Publication
n°307, pp. 246-255.
22. Oudin, L., Andréassian, V., Rojas-Serna, C., Le Moine, N. & Michel, C. 2007. Testing
similarity indices to reduce predictive uncertainty in ungauged basins. IAHS
Publication n°313. IAHS Press, Wallingford, pp. 303-310.
23. Oudin, L., V. Andréassian, C. Perrin, C. Michel, and N. Le Moine. 2008. Spatial
proximity, physical similarity and ungaged catchments: confrontation on 913 French
catchments, Water Resour. Res., 44, W03413, doi:10.1029/2007WR006240.
24. Perrin, C., Oudin, L., Andréassian, V., Rojas-Serna, C., Michel, C. & Mathevet, T. 2007.
Impact of limited streamflow knowledge on the efficiency and the parameters of
rainfall-runoff models. Hydrological Sciences Journal 52(1), 131-151, DOI:
10.1623/hysj.52.1.131.
25. Perrin, C., V. Andréassian, C. Rojas Serna, T. Mathevet, N. Le Moine. 2008. Discrete
parameterization of hydrological models: evaluating the use of parameter sets
libraries over 900 catchments. Water Resources Research, 44, W08447,
doi:10.1029/2007WR006579.
26. Randrianasolo, A., Ramos, M.H., Andréassian, V. 2011. Hydrological ensemble
forecasting at ungauged basins: using neighbour catchments for model setup and
updating. Advances in Geosciences, 29: 1-11, doi:10.5194/adgeo-29-1-2011.
27. Ribatet M., Sauquet E., Grésillon J.M. & Ouarda T.B.J.M. 2007. Usefulness of the
Reversible Jump Markov Chain Monte Carlo Model in Regional Flood Frequency
Analysis. Water Resources Research, 43, W08403, doi:10.1029/2006WR005525.
28. Ribatet M., Sauquet E., Grésillon J.M. et Ouarda T.B.J.M. 2007. A Regional Bayesian
POT Model for Flood Frequency Analysis. Stochastic Environmental Research and
Risk Assessment (SERRA), 21 (4): 327-339. doi:10.1007/s00477-006-0068-z
29. Rojas-Serna, C., Michel, C., Perrin, C. & Andréassian, V. 2006. Ungauged catchments:
How to make the most of a few streamflow measurements? IAHS Publication n°307,
pp. 230-236.
30. Sauquet E. 2006. Mapping mean annual river discharges: geostatistical developments for
incorporating river network dependencies, Journal of Hydrology, 331 (1-2): 300314. doi: 10.1016/j.jhydrol.2006.05.018
31. Sauquet E., Gottschalk L. & Leblois E. 2000. Mapping average annual runoff: A
hierarchical approach applying a stochastic interpolation scheme, Hydrological
Sciences Journal, 45(6), 799-816.
32. Sauquet E., Krasovskaïa I. & Leblois E. 2000. Mapping mean monthly runoff pattern
using EOF analysis, Hydrology and Earth System Sciences, 4(1), 79-93.
33. Sauquet, E., Catalogne, C. 2011. Comparison of catchment grouping methods for flow
duration curve estimation at ungauged sites in France. Hydrology and Earth System
Sciences, vol. 15, p. 2421-2435
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34. Sauquet, E., Gottschalk, L., Krasovskaia, I. 2008. Estimating mean monthly runoff at
ungauged locations: an application to France. Hydrology Research, vol. 39, n° 5-6,
p. 403-423
35. Snelder, T., Lamouroux, N., Leathwick, J.R., Pella, H., Sauquet, E., Shankar, U. 2009.
Predictive mapping of natural flow regimes of France. Journal of Hydrology, vol.
373, p. 57-67.
36. Varado, N., Braud, I., Galle, S., Le Lay, M., Seguis, L., Kamagaté, B., Deprataere, C.,
2006. Multi-objective assessment of the Representative Elementary Watershed
approach on the Donga catchment (Benin) using a downward approach of model
complexity. Hydrology and Earth System Sciences, 10, 427-442.
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