At the recent EGU meeting in Vienna there was a splinter meeting, organised by the International Association of Hydrological Science (IAHS) and chaired by Alberto Montanari, to discuss a new decadal programme to follow the Prediction of Ungauged Basins (PUB) initiative which is due to finish this year. IAHS has no money to support a research initiative, other than organising meetings, but the PUB initiative has been an important focus for research since it started in 2003. The PUB Science Plan can be found at . The final PUB meeting will be held in Delft in October (see ). PUB will result in two publications on the scientific progress and practice to be published by IAHS later this year. There was also a special session at EGU on the theme of a Visionary Session for the Next Hydrological Decade with invited presentations from Gordon Young (current president of IAHS), Thorsten Wagener, Huub Savenije, Xavier Sanchez-Vila, Peter Grathwohl, and Keith Beven. The full programme and abstracts are available at .
Unfortunately I had to miss some of the talks because of clashes with papers in other sessions but the theme that was common to both the splinter meeting and visionary session is that the new decade should address the impacts of change in catchments. It was clear that this meant different things to different people, from the co-evolution of hydrology and society, to the long term impacts of pollution, and the uncertainty of trying to make statements about future climate change. What was common to all, however, was the view that the stresses to society resulting from change and long term trends were going to be serious and needed to be addressed with some urgency.
It is perhaps worth noting that the prediction of ungauged basins was (and is) really an impossible problem. We simply do not have enough information about catchment characteristics to be able to predict the response of ungauged areas with any certainty. PUB was, however, successful in the sense of encouraging a new look at the problem and the science plan was quite explicit in recognising the difficulty of the problem and in suggesting that it was an issue of trying to constrain the uncertainty in making such predictions. The prediction of change is also an impossible problem. In this case, the dependence of hydrological predictions on the specification of boundary conditions is the issue. We simply cannot know enough about future boundary conditions (remember that those arising from climate change models are only scenarios with very specific assumptions, and even then they need fixing by bias corrections and downscaling methods before they can be used with hydrological models).
We also cannot know enough about boundary conditions in looking at past change and I also made the point in my talk that except in some rather extreme cases of catchment change, our data are not generally good enough for assessing the impacts of past changes. I therefore made the argument for using the initiative to commission designs for new, more accurate, measurement systems for all the hydrological variables we need: discharge, catchment precipitation, actual evapotranspiration and changes in catchment storage. It would be possible to use a design process similar to that used in the specification of satellite and astronomical instrumentation. I seem to remember that I made a similar suggestion at the beginning of PUB, since one solution to the ungauged catchment problem is to make measurements at a proportional level of investment. Observational techniques have improved over the last 10 years of course but are still not adequate for doing hydrological science properly. Given what depends on future catchment water management and its evolution with global society, this would seem to be an investment worth making.
If you would like to contribute to the discussions about the next hydrological decade or simply read what has already been posted, there is a public blog run by Alberto Montanari at . When he arrived, he thought it natural that clarendon hall students would play scott’s branch high in sports
