Topic 3: Ungaged Catchment Hydrology
Irstea participants:
Vazken Andréassian
Pierre Javelle
USGS participants:
Julie Kiang
Stacey Archfield
Rodney Knight
Lauren Hay
Background
The production of a model that does not require any calibration can be seen as a long-term
objective of hydrological science, but hydrologists worldwide are still far from having reached it.
Most of the current 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. Both Irstea and USGS have ongoing projects to
improve upon existing methods, and this research was presented during the day’s discussion.
Several areas of mutual interest for future collaboration were identified, including some
opportunities for immediate collaboration.
Opportunities for immediate collaboration
1.1 Catchment similarity
In order to transfer parameters from a gaged location to an ungaged location, it is necessary to
identify a suitable “donor” gage. Measures of catchment similarity are used to identify potential
donor gages. Vazken Andréassian presented a “parameter swapping method” to define
catchments similarity and this method will be tested on U.S. basins. Discussion and comparison
of U.S. and French results will be undertaken through conference calls and sharing of data and
model results.
1.2 Upcoming IAHS workshop
The next IAHS assembly will take place in July 2013 in Gothenburg (Sweden). Vazken
Andréassian is chairing a workshop (HW15) on "Testing simulation and forecasting models in
non-stationary conditions". He would welcome a contribution from USGS, who could participate
actively by making available a long-term hydrologic time-series on a non-stationnary (possibly
urbanizing) catchment. Lauren Hay and Julie Kiang will provide a suitable dataset for this
effort.
Prospects for mid to long term collaboration
A number of topics are of interest for ongoing collaboration between Irstea and USGS. These
are outlined below.
2.1 Ongoing actions
2.1.1Continue the work on catchment similarity
2.1.2 Continue the work on non-stationary catchments
2.2 Methods to improve calibration
2.2.1 Use of miscellaneous measurements, including individual gagings (measurements)
and partial records.
2.2.2 Diagnostics for streamflow record quality
2.2.3 Merging statistical (runoff-runoff) and hydrological (rainfall-runoff) approaches,
including methods for estimating flow duration curves
2.3 Uncertainty
2.3.1 Post-treatment of simulations & uncertainty
2.3.2 Uncertainty in streamflow measurements and records
2.4 Intercomparison of methods to evaluate extreme events
2.5 Water accounting & water census
Resources required
In order to carry out more extended collaboration, Irstea and USGS scientists need to be able to
meet to discuss specific research approaches, data, and tasks. This is most practical through
additional face to face meetings. Funds to allow periodic travel will facilitate additional
collaborative research.
In addition, funding for Irstea or USGS scientists to carry out this work would be extremely
useful. In particular, opportunities for joint PhD students or postdoctoral fellows would greatly
enhance both agency’s abilities to further progress on these topics.