Discussion – The new Science Initiative of IAHS

Read all comments from beginning of discussion

The discussion hosted on this web page is dedicated to the new Science Initiative of the International Association of Hydrological Sciences (IAHS), to be launched in 2013. The aim of the discussion is to identify key scientific challenges for hydrology in the near future, therefore shaping the main focus of IAHS in the next years. Background on IAHS and how the initiative came about is given in the page “About the IAHS new Science Initiative” whose link is provided in the above menu.

Devising a scientific initiative in hydrology is an exciting and stimulating task. Such an ambitious target calls for a community brainstorming activity. In fact, a science initiative is indeed a community effort: ideas must reflect the feeling of as many scientists as possible. Although communication means are very efficient today, to launch a public discussion on scientific questions for the future and to draw a synthesis of its output is indeed a challenging aim.

When I was invited by IAHS to devise and moderate this discussion I felt very much honored. I think this is an extremely interesting experience that I accepted enthusiastically, but I immediately realized that I really need the help of the whole IAHS to carry out the task well. For this reason, after consulting with numerous colleagues and the IAHS Bureau, I decided to open this blog, which I hope will be able to reach out extensively to all IAHS members.

The question that I would like all readers to address is:

“What is your view on the most exciting research challenges for hydrologists in the next 10 years? What are the core questions hydrologists should address that will get a worldwide attention from the community?”

I sincerely hope that this public discussion, which will last for about 6 months, can effectively catch the attention of the IAHS community. I would like everybody, and in particular young scientists, to freely share their thoughts without being shy or concerned about whether their opinions fit in. Any suggestion could be the opportunity for all of us to get in touch with colleagues who could provide a substantial contribution during the subsequent development of the initiative. Summarizing the results of the discussion and writing a draft science plan is a daunting task for which we clearly need a diversity of views.

If you are still in doubt whether or not you should leave a comment on this blog, please contact me.

I am honored to have the opportunity to trigger the discussion by providing my view on the above key question. I’ll be very brief for now, because I want to leave the discussion fully open. Other TF members will provide their thoughts in the near future.

I do have some personal observations. I think one of the most exciting challenges for hydrologists in the future is to better understand how hydrological systems and processes react to changing conditions and forcings, in relation to societal development. In fact, water is facing rising pressures due to increased demands from a growing human population and changing lifestyles, and decrease of freshwater resources due to over-exploitation, land use and land cover changes, and resulting environmental pollution. This is the consequence of efforts to improve the quality of life and therefore it is a positive development. However, the sustainability of this development is questionable.

In fact, in many parts of the world the poor distribution of freshwater in relation to demand is already the cause of water scarcity, which may be exacerbated by climate change (Kundzewicz 2007; Koutsoyiannis et al., 2009; Blöschl and Montanari 2010; Wagener et al., 2010). Moreover, the effect of human activities on the water cycle is deepening and widening rapidly across the planet, driven by increased demands for energy (King and Webber 2008; Koutsoyiannis et al., 2009), water (Jackson et al. 2001), food (Vörösmarty et al., 2000) and living space (Zhao et al., 2001).

Therefore, relevant scientific questions arise about the sustainability of the above changes for hydrological systems and the related effects on society. To improve the societal management of natural resources implies gaining an improved understanding of hydrology. This is an evergreen of hydrology research but –alas – so much remains to be done. In particular, we need to gain a better insight into how water systems react to (rapid) change, by analyzing the two-way connection between society and these water systems (Sivapalan et al. in press, HP). In the non-linear, dynamic interplay of people and water systems complex and very surprising patterns may arise and these we need to understand for being prepared for the future water challenges.

In particular, to distinguish between human induced changes and hydrological variability seems to be a key issue to better understand the interaction with society and how changes will evolve in the future. Identification of change requires a better understanding of variability as a function of space and time scales.

What are the reasons for variability and how does variability scale across time and space? What are the footprints that may allow one to recognize change in (rapidly) varying signals? What are the reactions of systems to change and variability? What about the predicting capabilities? These are deep science questions and at the same time relevant for water management.

The above thoughts make me think that “change”, “variability” and “society” are likely keywords for hydrology in the near future. I believe that meaningful answers to the above questions require a deep understanding of the interactions of hydrological systems and humans in an interdisciplinary framework.

As I said, I would like not to go into details at the present stage. I am looking forward to numerous spontaneous feedback from all of you to better shape the above thoughts! Disagreement is particularly welcome.

Thank you for your interest.
All the best,

Blöschl, G., Montanari, A., Climate change impacts-throwing the dice? (vol 25, pg 374, 2010), Hydrological Processes, 24, 1094-1094, 2010.
Jackson, R. B., S. R. Carpenter, et al., Water in a changing world, Ecological Applications 11, 1027–1045, 2001.
King, C., Webber, M., The Water Intensity of the Plugged-In Automotive Economy, Environmental Science and Technology, 42, 4305–4311, 2008.
Koutsoyiannis, D., C. Makropoulos, et al., HESS Opinions: Climate, hydrology, energy, water: recognizing uncertainty and seeking sustainability, Hydrology and Earth System Sciences, 13, 247–257, 2009.
Koutsoyiannis, D., Montanari, A., Lins, H.F., Cohn, T.A., Climate, hydrology and freshwater: towards an interactive incorporation of hydrological experience into climate research, Hydrological Sciences Journal, 54, 394–405, 2009.
Kundzewicz, Z. W., Mathematical modelling of ecohydrological systems in the changing world. Wetlands: Monitoring, Modelling and Management. T. Okruszko, E. Maltby, J. Szatylowicz, D. Swiatek and W. Kotowski, 151-159, 2000.
Sivapalan, M., Savenije, H.H.G., Blösch G., Socio-hydrology: A new science of people and water, in press on HPToday, 2011.
Vörösmarty, C. J., P. Green, et al., Global water resources: Vulnerability from climate change and population growth, Science 289(5477), 284–288, 2000.
Wagener, T., Sivapalan, M., Troch, P.A., McGlynn, B.L., Harman, C.J., Gupta, H.V., Kumar, P., Rao, P.S.C., Basu, N.B. and Wilson, J.S. 2010. The future of hydrology: An evolving science for a changing world. Water Resources Research, 46, W05301, doi:10.1029/2009WR008906.
Zhao, M., Pitman, A. J., Chase, T. N., The impact of land cover on the atmospheric circulation, Climate Dynamics, 17, 467–477, 2001.

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22 Responses to Discussion – The new Science Initiative of IAHS

  1. Demetris says:

    Alberto and all IAHS officers,

    I congratulate you for the way you shape the new Science Initiative of the IAHS.

    I wish to start with a very didactic story which was unfolded just last week. The story is about hurricane predictions and, even though it is not a pure hydrological story, I think it has some relevance to hydrology; the article entitled “Extended Range Forecast of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2012” by Philip J. Klotzbach and William M. Gray (available from http://hurricane.atmos.colostate.edu/Forecasts/ ) is worth reading by hydrologists. Its abstract starts: “We are discontinuing our early December quantitative hurricane forecast for the next year” and continues: “Our early December Atlantic basin seasonal hurricane forecasts of the last 20 years have not shown real-time forecast skill even though the hindcast studies on which they were based had considerable skill”.

    These scientists are admirable for their continuous efforts for two decades to tame an important prediction problem, but above all for their integrity to admit that their hypothesis proved wrong. The distinction of “hindcast skill” versus “forecast skill”, or else, model fit on past data versus real predictive capacity for the unknown future, is well recognized in hydrology. Yet we often tend to get fooled by skilful fits and provide profound explanations why the past phenomena happened–but the future will tell us our limitations.

    There is nothing wrong if some scientists are working on a hypothesis that eventually will prove wrong or on a direction that will prove to be a cul-de-sac. However, it is a problem if the entire community is headed for such a direction. Therefore, a Science Initiative for hydrological community is not an easy task. Over-certainties about which is the right direction, or which core questions should be addressed, may be dangerous. Perhaps a diversity of directions and core questions is the antidote for getting trapped in deadlocks.

    Two decades ago, the aspiration of deterministic predictability via a reductionist approach stimulated and even excited the hydrological community. One decade ago, the direction toward a radical reduction of uncertainty of hydrological predictions, even without data, was regarded to be a realistic target. Even today, many of us believe that it is a matter of one decade more or so to eliminate uncertainty and render useless any probabilistic/statistical/stochastic approach aimed to quantify uncertainty. Many of us believe that uncertainty can be, in principle, eliminated. Fortunately, however, this will never happen–that is my strong conviction. If it could happen, a world without uncertainty would not be livable (because predictability entails controllability) and fun (I cannot imagine anything fun if everything is expected).

    Two centuries ago, Sadi Carnot determined an upper limit to the efficiency of heat machines. After that time, a hypothetical machine exceeding this limit is called a perpetual motion machine of the second kind and is not part of science and engineering. This is because it violates the Second Law of Thermodynamics, which is related to the tendency of entropy to become maximal. Today, thanks to Boltzmann, Gibbs, Shannon and others, we know that entropy is uncertainty quantified. Thus, in my view, the aspiration of elimination or radical reduction of uncertainty could be compared to the quest for a perpetual motion machine of the second kind.

    Given the complexity of hydrological systems, determination of upper limits for the efficiency of hydrological predictions, is not as easy as in heat machines. But, I think, it is very useful and didactic to demonstrate the existence of limits and quantify these limits at least in some simplified systems.

    This is just one problem whose study would be useful from a philosophical and practical point of view–and I believe that both philosophy and practice are very relevant in discussions about shaping a Science Initiative. More generally, I believe that the new Science Initiative of the IAHS, instead of continuing the current trend of exorcizing or ostracizing uncertainty, should embrace and feature it. Trying to re-conciliate hydrology with uncertainty would be beneficial from a scientific point of view, because it would disburden hydrology from deterministic myths, from a social point of view, as it would give a more pragmatic basis in decision making, and from an educational point of view, particularly because it would provide students with important qualifications and skills to handle difficult problems in which naive deterministic approaches fail.

    Demetris Koutsoyiannis

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  2. Hilary McMillan says:

    Dear IAHS members,

    I am excited to be part of the discussion of the new IAHS Science Initiative. I have written here some initial thoughts, and hope to contribute more to the progressing and evolving conversation.

    For me, an important theme for the next decade is the global nature of hydrology and water research. This encompasses several aspects: the international challenges of understanding and managing water quantity and quality, the interaction of water with our global society, and importantly, the need to bring together diverse hydrological knowledge and data in order to make progress in our science.

    On the last point, some research initiatives and directions already underway come to mind. The setting up of virtual observatories or data repositories to learn from comparisons of hydrological behaviour and regimes, get best value from existing data and identify data and knowledge gaps. Using regional studies to understand why and how hydrological behaviour changes under environmental gradients, and what that means for our ability to predict. Moving away from purely local studies and towards research into underlying structure. Catchment classification as a means to synthesise hydrological knowledge. And bringing together hydrologists from different backgrounds (e.g. modellers and experimentalists) to encourage new directions as disciplines and ideas meet.

    My feeling is that the key to PUB’s success was its inclusivity, raising questions that every hydrologist can relate to. I hope that the new decade will achieve the same, whatever the final wording and focus.

    Hilary McMillan

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  3. ritesh arya says:

    Congratulations for the new initiative
    This is timely venture by IAHS and would help in building a strong foundation in hydrological research in the next decade.

    I personally feel that understanding of MOUNTAIN HYDROLOGY & HYDROGEOLOGY holds the key for solving all issues related with water problems for simple reason that they are the HEAD WATER regions of the world. Like head in our body is supreme organ and our body functions properly if our mind is stable or similarly water systems functions properly if our Head Waters are properly understood. It is pity that today mountain hydro geological process are poorly understood. Right from the process of glacier formation, glacier melting, snow melt ablation,water in streams, formation of rivers and recharging of groundwater all are processes interlinked with either stable habitations in low lying areas or disruption due to flooding or flash flooding.
    Proper management and timely recording of scientific data holds the key for sustainable development in the mountain river basins which are neglected at present because of obvious reasons.
    Geographical isolation, extreme climatic, complex geological conditions, non availability of good monitoring instruments and labs specially in Asian-African countries are responsible for vacuum created in this area of hydrogeological research. As a result water system in our River basin where billions of people live are poorly understood.
    We should never forget MAJOR CIVILISATIONS (Indus, Mesopotamian Nile etc) in the past were destroyed not because of big fights or battles but for simple reason of MAJOR FLASH FLOODS which shook the very basis of their existence.
    Climate change is a reality…….we are in global warming times but soon would be entering into cooling times. May be we have escaped wrath’s of flash flooding events this time but who knows when we will be in trouble and meet the similar fate as suffered by older civilisations in the past.
    Monitoring of Polar glaciers specially in Arctic region in comparison to Himalayan glaciers should be given importance for simple reason that Major glaciers in Himalayas have already been extinct or are in the verge of extinction. The impacts of flooding in the past did lead to extinction of civilisation but now it the time of Polar glaciers. Slight melting of the Ice cover will have wide ranging influence on major cities of Europe which are thriving on major river systems. Impact of life on Coastal areas is another big threat.
    This in no way mean way means that Himalayan glacier catchment can be ignored.Today though the glaciers have receded significantly but still they sustain billions and in the last decade Hydro power generation has also contributed to Energy security in the region.
    Proper monitoring of these mountain glacial catchments holds the key for sustainable water and energy development in the region but also holds the key for providing economical sustainable habitat in years to come.

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  4. ismail Gultepe says:

    Variability and measurements
    I feel that in the future hydrologists should think about working together more with other natural science groups e.g. meteorologists, ecologists, oceanographers… Hydrological systems include water at the surface, in the air, and in the ocean. Variability is a key point because it affects deterministic relationships; for this reason, deterministic approaches should represent this variability; otherwise, they will not work when they are used in the prediction models. I call myself hydrometeorologist because i am interested in meteorological processes in the atmosphere that affect water cycle at the surface. It will be a key point to focus on how meteorological processes will lead to variability in the hydrological cycle? Do we measure hydrometeorological parameters accurately in the air and at the surface? For example, do we know measure snow intensity and amount accurately? Do we know how to measure snow over the Arctic regions versus mid-latitudes? or or over mountainous regions? Can we estimate precipitation at the surface from remote sensig retrievals? There are many deterministic ways to do it, which one is correct? Can we put our deterministic approaches into the models for this areas? If we we cannot measure it, how can we predict it?

    Meteorological and hydrological systems are very complex and variability is very large. Therefore, uncertainity in the predictibility is very large. To reduce it we should study individual cases and extreme situations, and our results should represent variability accurately. We can add various items to focus on “snow measurements”, “Arctic hydrometeorological systems”,”integrated models”,”Variability”,”Human induced changes”,”climate changes effects on hyrological systems”,” extreme weather events and hydrological processes”,” Disasters in the Arctic Environments”,”Mountain Hydrology”,”Precip intensity and floods” etc.

    Ismail Gultepe
    Cloud Physics and Severe Weather Res. Sec.
    Environment Canada, Toronto, canada

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  5. Salvatore Grimaldi says:

    Dear Alberto, Dear distinguished IAHS community,

    I am really glad to see this blog, following the exciting meeting held in Melbourne where the IAHS President launched this think tank. So I am happy to give here my contribution just sharing some feelings I have.

    I started my academic career more or less 10-12 years ago and if I look behind I realize that I was witness of an incredible change in the research approach due to the internet diffusion and by the computational power evolution. This impressive and fast transformation had a great impact in the research in general and also in our field.

    At the same time, and in the same way and rapidity, I am now realizing how is changing the technological level in hydrological observations.

    If I think on what is happening in term of remote sensing, image analysis and sensors, and the related amount and quality of data that soon will be freely available, surely my feeling is that we need to move! we need to be ready in few years to use it in an appropriate way! we need to transform hydrology in modern hydrology!

    I am pretty sure that in 10-20 years it will be freely available for the entire planet digital elevation models at one meter of resolution and probably the vegetation and soil use characterization will be available too. Radars and satellites will provide us rainfall and soil moisture information at the desired spatial and time resolution. Cameras will be able to counts rainfall drops while they fall down and probably cameras will tell us also the velocity of surface water in real time making anachronistic rating curves and discharge observations.

    I could continue with many other examples but I prefer to conclude just telling that my feeling is that we are entering in a new age where hydrologists should adapt theories and models to the new technological opportunities. The impressive advancement in all disciplines will allow us to find useful solutions for many hydrological problems…..so probably in the next ten years we need to look around and change our hydrological perspective without worrying that something is not possible!

    Happy Christmas!

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    • Demetris says:

      Dear Salvatore,

      I understand your excitement about new technologies. I agree with you about their usefulness in observing hydrometeorological processes. However, I find that the optimism implied by your phrase “without worrying that something is not possible” may be misleading or even hubristic. Such optimism looks like that triggered by the power of computers, making people think that they would resolve any real or imaginary problem. Now you think that cameras will be able to count rainfall drops while they fall down. Indeed our life is full of cameras nowadays–but if you want to count all rain drops over the globe, you may need even more… Personally, I am not excited to use such information, nor I believe that hydrology could benefit by using lots of cameras. I doubt that even for TV: are TV programmes better now than were couple of decades ago, when much fewer cameras were in use?

      Have you tried to compare satellite rainfall estimates with ground data, before the former have been adapted to match the latter? I do not say that new observation technologies are useless, but I believe the information contained in the traditional ground observation networks is indispensable. We should, thus, respect, keep alive and even try to improve these networks, resisting to trends that modern technologies render traditional networks useless and can make everything possible.


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      • Salvatore Grimaldi says:


        of course you are right, your point is clear, and I also agree with you. However, what I wanted to emphasize is that, in my opinion, when you are going to improve a methodology or model you should have clear in mind which are the boundary conditions or initial conditions. The new age of hydrological observations will and should be the starting point of the next generation models, so it is important to take into account what the new technologies can do for us, and probably we are not aware on their potentiality. As twenty years ago someone saw the capability of digital topography and remote sensing, at the same we should look around to verify the possible contribution of other disciplines.

        Happy new year!

        PS: I will gift you a new camera :-) ))

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  6. Fenicia says:

    It was a good initiative to set-up this blog, let’ see if this will help us to find a democratic consensus (and please participate!).

    I read with interest all your comments and ideas. I think it would be useful to discuss how we are going to judge and rank all these proposals and the ones that will come. A debate on how the theme for the next IAHS decade should look like (i.e. which requirements it should have), would probably contribute to focus and streamline the discussion. I am going to list some basic requirements hereafter.

    • It should be something that is able to capture the attention of a large community. Hydrology is highly multidisciplinary, with ‘modellers’, ‘experimentalists’, geographers, statisticians, geologists, etc. Everybody should be able, in one way or the other, to contribute. Hence, it should not be something that favours too explicitly a restricted group of researchers (although some choices are inevitable at some point).

    • On the other hand, it should be specific enough to be about hydrology, and to help hydrological science to maintain its identity. I this respect we should not forget that hydrology is essentially about trying to improve our understanding of how catchments work.

    • It should take into account speed of progress in research, and in particular that progress is slow. We have witnessed a lot of advances in the last years, but we are also searching for the answer to questions that have been posed half a century ago… Where does the water go when it rains? Which ‘hydrologic laws’ operate at the catchment scale? … This is to say that 10 years is not much for research, and asking hard questions is easier than finding the answers…

    • It should be something appealing to a wide public. Ideally not too self-referential, connected to practical problems that society considers important.

    • … And more to add, if you will.

    I think a balance of all this aspects would be desirable, and I think it will be difficult to find it. But I guess this should be the point of the discussion. Looking forward to your comments.

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    • Bettina says:

      I would add as a “requirement” that the theme should be appealing to funding agencies. One of the strength of PUB was that it provided a common ground for numerous national and international proposals.

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  7. Ciaran Harman says:

    I want to thank IAHS for hosting this discussion and Alberto Montanari in particular for taking on the challenge of stimulating and moderating it. I’ll bet it isn’t an easy thing to get people to take time out of their schedules to talk about the future of the discipline – at least not unless there is beer involved.

    First, since Alberto has asked for disagreements: A response to some of the previous comments. Demetris Koutsoyiannis argues that instead of exorcising uncertainty we should embrace it, and feature it. It is surely true that a science with no error-bars is a poor science indeed. Other comments have focused on the flood of data that is cascading toward us, accelerated by exponentiating computation power. There is a temptation to meet this flood by making the technological opportunities for improving prediction the focus of hydrologic science. However, I would suggest (in the spirit of good-humored provocation) that this is a mistake.

    As much as providing predictions (qualified by the appropriate uncertainty) has been and will continue to be the primary social motivation for hydrology, it is important to remember that the central intellectual motivation of a true science is the deeper revelation of truth and beauty. Is there nothing to discover in the hydrosphere? No mystery to be unraveled? Is our role a merely technological one of characterization and modeling? Or can we focus instead on discovery and explanation as motivating impulses, seeking insights into the true nature of hydrologic systems?

    25 years ago Jim Dooge proposed that we see to discover “hydrologic laws”. These are laws that apply at the scale of watersheds, rather than at the scale of the individual processes operating within them. But a quarter of a decade later, what progress can we claim towards this? I would argue very little. Some will be unmoved by such abstract aims, and prefer to build and calibrate more models. But even for those with such applied ends, there are good, applied reasons to search for such laws – they offer the possibility of new ways to parameterize a hydrologic model (and the Representative Elementary Watershed concept provides a ready-made framework to integrate them).

    Furthermore, we must find a way to confront the greatest ‘applied’ challenge we face: dealing with change. The world is changing rapidly, not only through climate change, but also with changing landuse and changing demands on water resources. More complicated and data-hungry models will be demanded and will be constructed – with or without the help of an IAHS initiative – when what is truly needed is wisdom and insight.

    How do we gain insights into the causes, trajectory, and consequences of changing hydrologic systems? Perhaps:
    By looking to the past: watershed are not conjured out of the sky for us to examine. The have a history as geologic, climatic, ecologic and anthropogenic creations. Hydrologic history is not so clearly recorded in sediments and pollen records, but the profound role that hydrology plays in shaping landforms and ecology has given us the tools to begin to reconstruct past hydrologic change, and connect it to the evolution of landscapes and climates.
    By comparing across places: what makes places different from each other today, and how will this affect the way they respond to future changes (sensitively? resiliently?)? Describing the behaviour of each watershed as the unique result of its particular history is true up to a point, but there are patterns that transcend and connect the behavior across places. The Budyo curve offers the most rudimentary yet profound example of this.
    By developing good explanatory theories: An explanatory theory differs from a mechanistic process description in that it connects the effects (or phenomena) that we can see to causes that may be unseen. Beyond explaining the hydrologic behavior we observe in a watershed, can we explain how that watershed’s hydrologic ‘system’ has come about? Can we explain the pattern of variation in hydrologic systems between places? Having good, quantitative explanatory theories of these would help give us the wisdom and insight to better deal with the uncertainties of the future.

    A brief aside: The current paradigm of hydrologic models make for weak explanations. David Deutsch (in The beginnnings of infinity, see also here: http://www.youtube.com/watch?v=folTvNDL08A) recently suggested that a good explanation is one that is ‘hard to vary’. That is, one in which the truth of the component predicates interdepend on each other in such a way that the variation of any causes the whole thing to collapse. Hydrologic model fail this in two ways. Firstly there is the well-articulated issue that equifinality allows for a large amount of variation in internal model states to account for the observed behavior – thus our limited ability to predict the future even with a well calibrated model is unsurprising. But a less common issue is not so well acknowledged: that most hydrologic models can happily simulate any arrangement of fluxes and storages, regardless of whether such arrangements actually exist. That is, they are few fundamental constraints on the way a watershed may behave, apart from requiring that mass, energy and momentum be conserved. Actual watersheds, because they are not arbitrary constructions but rather have a long history of evolution, have a narrower range of possible configurations. The constrains implied by the limited possible trajectories of landscape evolution (vast though that range of trajectories is) do not yet have a place in hydrologic theory.

    In short, I hope that Hydrology can be a discipline where fundamental discoveries are made about how landscapes work, how they have come to be that way, and how their functions will change in the future. I hope that there is room in the IAHS initiative to help foster this perspective.



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  8. In the interests of clarity, let me edit that brief aside a little:

    “But an issue is not so commonly acknowledged: that most hydrologic models can happily simulate any arrangement of fluxes and storages, regardless of whether such arrangements are likely to exist in the real world. That is, the models encode few fundamental constraints on the way a simulated watershed may behave, apart from requiring that mass, energy and momentum be conserved.”

    Better. Thanks!

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  9. Christian Stamm says:

    Dear Alberto, dear colleagues

    thanks for having started this broad discussion on where hydrology should go within the new IAHS Science Initiative. As pointed out by Alberto, this activity should start with a community-wide brainstorm activity before we can proceed and try to condense the content at a later stage.

    Accordingly, I try here to contribute to this brainstorming activity with some initial thoughts. Working mainly in the field of hydrology and water quality impacted by human activities and doing research, which often has an applied character I try to summarize this input as follows:

    Providing a sound scientific basis for adaptive management of water resources under uncertainty.

    This heading entails several aspects I would like to briefly mention here:

    1. (Predictive) Uncertainty is considered an unavoidable aspect (whether one likes it or not). The really interesting question is how to deal with it: On the one hand, there is the question how we can successfully reduce predictive uncertainty (by improved observations and models and an optimal combination of both). Related to this aspect is the question how to deal with the scale mismatch between models and measurements AND the management scale. On the other hand, there is the question of how to quantify and characterize properly the remaining uncertainty.

    2. Adaptive management has been proposed as a way to deal with complex (evolving) systems which are only partly/poorly understood and which are influenced by evolving boundary conditions. However, it seems to me that this notion has remained more of a buzzword so far than a concept that provides substantial support for management. Part of this problem may arise from the fact that there is not much scientific underpinning for how to bring this concept into practice. Basic scientific understanding is required to give advice about appropriate temporal and spatial scales characterizing feedback loops between observations of the system and management actions. In this context it is important to consider the long time-horizons over which effects of management may be emerging.

    Although these points seem all to be centered around practical applications, I am not arguing that practice should be the guide for developing the research activities like this IAHS Science Initiative. Enhancing our fundamental understanding of hydrological systems and our possibility to predict them (and to understand to which degree they are predictable) will also foster better water resources management in the future (it’s not a guarantee though). One of the most powerful tools for practice is a good theory. Such theoretical foundations however, need to account for the fact many aspects of the hydrological cycles are impacted by human activities. Hence, we not (only) need theory for pristine catchments and watersheds, where one can observe “nature in action”, but also concepts that accommodate anthropogenic influence in an appropriate way. Hence, practice should not be the principle guide for developing research in this initiative but it should be used as valuable sounding board for the proposed ideas.


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  10. David Post says:

    Dear All,

    This is a great forum and will produce some very useful ideas for the topic of the next biennium I am sure. Alberto – you will have your work cut out for you in summaring all of these comments in a sensible way I am sure, however hopefully themes will emerge which may at least point the broad direction for where we as a hydrological community need to go.

    Personally, I work on understanding hydrological response under changing conditions, so will of course give a big thumbs up to Alberto’s initial suggestion, and I’d be very surprised if the concept of adapting to changed or non-stationary conditions were not a major focus of the inititative (whether that be as related to climate or more direct human activities such as logging, forestry, farm dams, dams, etc etc.

    However, I do want to support the comments made by Salvatore. It seems to me that information is growing exponentially, and I do not believe that the hydrological community has been quick enough to take up these new sources of data. In many cases (myself included!) we are still using models that were first created decades ago. I wonder if we are all just too old? That’s a very good reason for encouraging younger hydrologists to join this discussion!

    I’m not sure that ‘incorporation of new data and technologies’ is a sufficient topic for the new IAHS Initiative in itself, but it should certainly be part of any proposed solution.

    I look forward to following others thoughts on this blog and contributin where I can.

    All the best,

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  11. Stan Schymanski says:

    Dear all,

    I also would like to thank Alberto for his great effort to kick-off and moderate an inspiring and important discussion.

    What makes a great theme for an IAHS Decade? In my opinion, it should be a challenging research question that a large part of hydrologists relate to and that is motivated by a great societal need.

    Prediction in Ungauged Basins (PUB) did just that, in that it responded to the permanent societal need to predict hydrological behaviour and at the same time challenged the common focus of using long-term observations from the past for “predicting” the future. The fact that many places in the world just do not have such long-term records has forced us to rethink our approaches rather than limiting ourselves to places that do.

    Today, ENVIRONMENTAL AND ANTHROPOGENIC CHANGE confronts us both with an immense societal pressure to deliver useful decision support tools and an exciting challenge to develop new knowledge that can safely be projected into the future. The new challenge is that projections into the future can no longer be guided by observations in the past to the same degree as they could when the boundary conditions were considered stationary.

    Even more than prediction in ungauged basins, projections into the future under change require a deep understanding of the underlying processes and things like self-organisation and adaptation of (eco-) hydrological systems. While prediction in ungauged basin was approached by many through similarity analyses with gauged catchments, this approach is no longer useful for prediction under change, as there are no analog catchments that are adapted e.g. to the atmospheric CO2 concentrations expected in 50 years time.

    The challenge of delivering decision support for managing our changing environment for a sustainable future has to be tackled from many directions at the same time and encompasses all of the challenges mentioned in previous posts, such as:
    - the estimation of uncertainty and feasibility of prediction,
    - multidisciplinary research,
    - the interaction between society and water,
    - the understanding of headwater catchments,
    - the interplay between hydrological and meteorological systems,
    - the use of different emerging data streams for testing and informing models,
    - the search for general hydrologic laws and theory,
    - the reconciliation of the present with the past (and the future),
    - the reconciliation of theory with data and management practice,
    and many others that have not been mentioned yet.

    Just to illustrate how important environmental change is becoming in our thinking, I listed below hydrology sessions at EGU 2012 that explicitly mention change in their title:

    - HS2.3 Sub-Arctic Hydrology: Hydrological Processes, Modelling and Change in the Northern Hemisphere (http://meetingorganizer.copernicus.org/EGU2012/session/10286)

    - HS2.20 Earth Surface Systems in Transition: Experimentation, Observation and Modelling (http://meetingorganizer.copernicus.org/EGU2012/session/10319)

    - HS5.6 Climate Change and Impact on Drinking Water Supply (http://meetingorganizer.copernicus.org/EGU2012/session/10180)

    - HS7.4/AS4.17/CL2.10 Hydrological change versus climate change (http://meetingorganizer.copernicus.org/EGU2012/session/9221)

    - HS7.6 Climate change and water infrastructure (http://meetingorganizer.copernicus.org/EGU2012/session/10235)

    - HS8.2.9 Groundwater resources in a changing environment (http://meetingorganizer.copernicus.org/EGU2012/session/9209)

    - HS8.2.10 Groundwater Dependent Ecosystems – Impact of land use and climate change on ecosystem vulnerability (http://meetingorganizer.copernicus.org/EGU2012/session/9210)

    - HS10.8/BG4.4 Environmental and anthropogenic change and its effect on ecohydrological behaviour (http://meetingorganizer.copernicus.org/EGU2012/session/9170)

    For me, understanding and managing environmental and anthropogenic change is THE challenge of this century. Therefore, I think that it would be very timely and helpful to address this challenge in a new Science Initiative of IAHS.

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  12. Alberto says:

    Dear Alberto and all bloggers and readers,

    In addition to the challenges identified (see what’s above and what will follow), our suggestion is that, even more than in the past, hydrologists should study unstudied areas of the world. Even in the PUB initiative, which aimed to be inclusive, the fast majority of the studies were located in the well developed part of the world (i.e., United States and Europe).

    We are currently concluding a 3-week workshop on water resources management in Ethiopia and we can see the potential of studying the hydrology here, which is new to us, challenging and needed to solve real societal problems related to water. Ethiopia is an interesting example but what follows applies to many countries where, so far, hydrology has not been studied enough.

    Ethiopia is facing many challenges. The economy is growing, but still many people do not have basic services such as water, food, electricity or sanitation. Things are also changing. Fast. The landscape is changing. The climate is changing. The management of water is changing. Water is an essential component and there are problems to solve. The science of hydrology has a key role to play in solving these problems, but requires the mismatch between research and practice to be addressed (as pointed out by Christian). Who if not hydrologists should inform the decision makers about water issues.

    The fast changes happening here make Ethiopia an ideal laboratory for observing and understanding evolution of coupled human-water systems (the so called socio-hydrology). Deeper understanding can be gained in places like this, where changes are happening quickly, and where surprises (“black swans”) could happen in the near future and reveal previously unexpected evolutions. It may be the place for new discoveries (as Ciaran says), for starting to understand/model water and people, to try to anticipate future changes in their interactions, as well as to learn from our previous mistakes and not only apply the knowledge gained from other places.

    And what about the beauty of studying Ethiopian hydrology for its own sake? Ethiopia is climatically and environmentally extremely heterogeneous. This makes the spatial and temporal variability of hydrologic signatures very strong in the country. The highlands receive a lot of rainfall (more than 2000 mm/year) concentrated in only three months. Most of Ethiopian runoff is produced there (part of this water reaches the Mediterranean sea through the Nile river). Lowlands vary from forests to deserts. The hottest place on earth is here (the Danakil depression, more than 150 meters below see level). In Ethiopia comparative hydrology would be an extremely informative exercise and much can be gained by comparing and contrasting Ethiopian hydrology with the rest of the world (see Hilary’s post).

    In unstudied places, the importance of the new technologies for hydrological observations discussed by Salvatore is crucial as well as models developed related specifically to these new technologies. In places like Ethiopia the traditional measurement networks (i.e. stream/rain gauges) exists, but are not developed or supported as in US or Europe, and often (but not always) do not have long record measurements. We recognize the importance of maintaining these traditional measurements (we agree with Demitris), but this requires support, and there is a need to integrate them with new and less-expensive technologies now available (including remote sensing, whose potential has not been fully realized) or which will be available in the future.

    Last but not least, the interest and excitement for hydrology as a science is growing fast in Ethiopia. A new institution on water resources and a new education program (18 PhD + 24 MSc) has been started less than one year ago. This is a new generation of hydrologists which needs inputs/suggestion from the experienced people from our community in order to start the adventure of understanding the hydrology of their own country. Also the population as a whole is fully engaged. Recently all Ethiopians donated 100% of their salary for one month to fund the construction of the Renaissance Dam. From those we spoke to, most did this willingly, recognizing the importance of water resource development to their future and the future of their country.

    Now just substitute Ethiopia with East-Africa, or West-Africa, or India, or Peru, or …

    Alberto Viglione, James Cullis, Mekonnen Gabrimichael, Tena Alamirew, Chas Fant, Yohannes Gebretsadik, Amy Fant

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  13. Giuliano Di Baldassarre says:

    Dear Alberto, dear IAHS fellows, dear all,

    I have gone through this interesting discussion and found it extremely fascinating.
    I would like to focus on the need to better understand the behavior of coupled human-water systems and the opportunity given by the current proliferation of remote sensing data. Also, I would like to try to provide some concrete examples by referring to floodplain hydrology.

    I totally agree with many comments discussing the need to better understand the (changing) behavior of coupled human-water systems as natural (pristine) catchments have become more and more uncommon. This point is also well illustrated by the recent commentary by Sivapalan et al. (HP Today, in press), introducing the discipline of socio-hydrology.
    In floodplain hydrology, for instance, there have been tons of studies investigating the human impact (e.g. land use changes, river embanking, etc…) on the frequency and magnitude of floods. Besides, many social scientists have examined human adjustments to floods and, in particular, the so-called “levee effect”, identified by Gilbert White more than 60 years ago (i.e. paradoxically, building/raising levees might even increase overall flood risk as protection from frequent flooding changes the perception of risk and might encourage inappropriate development, which is then vulnerable to high-consequence and low-probability events).
    However, the feedback loops and reciprocal effects, not to mention surprises and threshold mechanisms, taking place in coupled human-water systems remain largely unexplored and poorly understood.

    I strongly believe that a great opportunity to improve our understanding is offered nowadays, as mentioned by Salvatore, by the current proliferation of remote sensing data. These data do allow an unprecedented possibility to observe catchment dynamics. Going back to the example of floodplains as coupled human-water systems, there is a growing quantity of remote sensing data, often globally and freely available, allowing the analysis of floodplain inundation patterns as well as changing human settlements across scales, hydroclimatic (and socio-economic) conditions, and levels of human impact. This can enable the investigation of emerging patterns and might trigger the development of new theories as hoped by Ciaran. Definitely, as pointed out by Demetris, “traditional ground observation networks” are still essential. Actually, I would say that ground data are even more crucial because most remote sensing algorithms, actually, do require sufficient ground truth information.


    P.S. Sorry Alberto, although welcomed, I could not find major points of disagreement!

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  14. M. Sivapalan says:

    I am following this discussion with interest, and get the feeling of déjà vu – the “more things change the more they remain the same”. We went through the same phase at the beginning of the PUB initiative. I distinctly remember a lot of that, including a lot of polemical arguments as well.

    A lot of neat ideas have been presented and discussed, and it appears some of the lessons of PUB (good and bad) have been taken to heart. For example, I liked Hillary McMillan’s comment (echoed by Febrizio Fenicia) that “PUB’s success was due its inclusivity, raising questions that every hydrologist can relate to”.

    I do realize that many of the issues related to PUB will not be solved with the end of the PUB Decade. And yet just extending the PUB Decade for another 10 years is not going to be adequate – that will be seen as “mission creep” – people will see it as bureaucratic, and is the surest way to kill excitement.

    There is no question that we have to think big, broad and profound (benefiting from all the progress we have made in the past decade), but in the end we also need to be practical. There is only so much and only certain kind of things that we can do internationally in an inclusive way. I believe that when we were developing PUB the big breakthrough (for me at least) was the (shocking) realization that there is only so much (and only certain kind of things) that we can we do with the funds that IAHS can bring to the table (which was practically zero).

    Nothing clarifies your mind better than that realization – in fact, for PUB it turned out to be the blessing in disguise. Indeed I attribute the success of PUB to the simplicity of the idea and the “low expectations” placed on it, which enabled us to do the simple things we can do with limited resources. We were not going after the moon (or Mars), although (by the way) this was an idea pushed by some (including, literally). We followed the motto of a Japanese research park located outside of Tokyo, which was “simple living, high thinking”.

    So, there has to be “freshness” to the proposed new initiative. Coming up with a new topic that is simple, inclusive, challenging, and yet achievable at the global level on the basis of excitement alone (and enlightened self-interest, but little funding), is going to be important.

    I know that Alberto Montanari is going to summarize these comments, so I am going to wait for that. However, one theme stands out in many of the thoughtful comments presented so far. This is the idea of “comparative hydrology” – that we can organize ourselves regionally and internationally to compare and contrast between catchments across climates, geographical regions, including across human-impact gradients (in an increasingly highly human impacted world), and interpret the resulting patterns in terms of not only the current state of these catchments but in terms of their geologic/climatic and also human history. As Giuliano Di Baldassare states, remote sensing data can increasingly be used to reveal hidden patterns, rather than merely being used as “grist to sophisticated models”. Comparative hydrology is the key to the kind of scientific discoveries (i.e. hydrologic laws of Dooge) that Ciaran Harman discussed. Ciaran knows (and has written about) that this is the key to the synthesis of Newtonian and Darwinian approaches that is needed for the pursuit of new hydrologic theories, and to ultimately assist with predictions in ungauged basins and under future changes.

    But comparative hydrology is also practical not only in terms of advancing predictions, but also in terms of serving as the vehicle to bring “people” together. This is brilliantly illustrated by the blog of Alberto Viglione et al. which brought together the experiences from their recent winter research workshop in Ethiopia. I was also there for a while and observed this workshop in action. A workshop that was ostensibly aimed at training Ethiopian students, turned out to be an educational experience for the supposed “trainers” themselves. In this sense, I believe that a focus on comparative hydrology, if designed well, also advances the notion of “inclusivity” and “empowerment” at many different levels including north-south, east-west etc. (which I feel is equally important).

    Once the nature of activities is decided, the naming of the initiative may naturally fall out of this, and so is not something to agonize over. Remember Shakespeare: “What’s in a name? That which we call a rose by any other name, would smell just as sweet”.

    Look forward to further discussions ….. great initiative by Alberto Montanari and IAHS.

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  15. Hoshin Gupta says:

    Thanks Alberto, for this thought provoking discussion.

    I will continue to give this some thought, but on initial reaction, I strongly agree with Stan Schymanski that
    “Predictions Under Changing Conditions”
    could and should be a new focus. The previous decade focused on
    “Predictions in Ungaged Basins”
    and this was broad enough and inclusive enough to engender widespread support
    while driving the science forward. Similarly “Predictions Under Changing Conditions”
    seems to me to be inclusive of all of the other suggestions – it poses the challenge of
    natural and anthropogenic non-stationarity, including human impacts (urbanization, agriculture), climate variation etc, while allowing for all of the science issues to be investigated including theory (very important), classification, comparative hydrology, uncertainty, new technologies, observations … etc etc.


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    • Demetris says:

      Dear Hoshin,

      I am following you in not following Siva’s suggestion implied by Shakespeare’s quotation he uses: “What’s in a name?”. I hope I do not depress the readers if I contrast the Shakespearian poetic mood with the cynicism of Antisthenes (~445-365 BC, founder of Cynic philosophy) who said «Αρχή σοφίας ονομάτων επίσκεψις» or “The start of wisdom is the visit (study) of names”. (By the way, I have used this quotation in my recent paper in JAWRA, 2011, http://dx.doi.org/10.1111/j.1752-1688.2011.00543.x , where I discuss the term nonstationarity perhaps viewing it in a way different than that you use it).

      Many examples illustrate the importance of names: see how popular certain phrases are (e.g. paradigm shift, self-organized, black swans, tipping points, etc.), also making famous their inventors. I believe that “Predictions in Ungauged Basins” was also a good name.

      But, don’t you think that “Predictions under Changing Conditions” is sort of tautology? If nothing changes, what’s the meaning to make predictions? Also, why give that emphasis to changing conditions? It may be true that many are keen to tell the future conditions for 2050 or 2100—also, there is no shortage of predictions for up to 100000 AD. Instead of getting excited to make or use such predictions, or getting frightened that things change, hydrologists have all prerequisites to stay cool. I think hydrology teaches that things change all the time; this is not modern knowledge (cf. “πάντα ρει / panta rhei”). Also, due to its close connection to engineering, hydrology, from its cradle, has been related to change; e.g. hydrological engineering studies are all about (mostly intended) change, as a result of engineering constructions.

      I will not propose alternative names, but, as I implied in my initial comment, I believe that the grandeur of “uncertainty” should be included in the new focus.


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      • Hoshin Gupta says:

        Hi Demetris,

        Yes, of course the phrase “Hydrology under Changing Conditons” is a tautology just as I always felt that “Predictions In Ungaged Basins” was (and is) a tautology (and in being so both inspired us and enabled us to study what needed to be studied) :-)

        The fact is that we have historically tended to study watersheds “as though” they were unimpacted (and stationary in character).

        (I think that) We need to shift the focus beyond this and acknowledge that, just as most basins are (in effect) ungaged, they are also impacted (i.e. undergoing change). I rather suspect that funding agencies will respond well to the idea since there are both scientific and practical (engineering/management) drivers underlying the science of hydrology.

        And certainly uncertainty is clearly important … and it has been so (i.e. considered important) for at least the past decade. So, lets keep that … and build upon it to study the (hydrological) world in a way consistent with the fact that it is continually changing (in a non-stationary way), thereby raising the level of difficulty (and thereby the level of the science).


        PS: Im not attached in any way to the actual words used :-)

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  16. Bob Su says:

    Interactions of the water cycle with other components of the Earth system should be the key emphasis of hydrological research in the new initiative. We should follow the scientific method as the cyclic or spiral evolution of observation, theorizing and experimentation, so that predictions can be made for further changes in water resources. We have formulated some themes in the upcoming CAHMDA-V workshop (Catchment Hydrological Modeling and Data Assimilation) to take place at ITC, University of Twente, 9-13 July 2012 (cahmda.itc.nl). Interested colleagues are most welcome to debate on the scientific contents. I have enclosed some information below for your information.
    Bob Su

    The 5th International Workshop on
    Catchment Hydrological Modeling and Data Assimilation (CAHMDA-V)

    “Catchments in a changing climate”
    ITC, University of Twente,
    Enschede, the Netherlands,
    9-13 July 2012

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  17. Stan Schymanski says:

    Dear Demetris,

    I would not agree with you that “hydrology, from its cradle, has been related to change”. What does a flood frequency curve teach us about change? A unit hydrograph? How does a calibrated model relate to change?

    To me, these 3 examples do show a progression to more and more inclusion of change, from nothing, to changing rainfall to changing everything except for the calibrated parameters.

    In all these approaches we assume some degree of stationarity, and the big challenge has always been to relax these assumptions. Maybe we should clarify what we mean by “changing conditions”. If we want to predict runoff, I would call everything that has an impact on runoff a “condition”. Now we can take whatever approach we want and look at what conditions are implicitly or explicitly assumed to be invariant. We will find that our current approaches rely on a lot of assumptions about invariant conditions (e.g. parameters of a hydrological model), or on assumptions how these conditions are going to change in the future. Any possible violations of these assumptions could lead to a wrong prediction, so proper consideration of uncertainty should quantify the probabilities and effects of such violations within the predicted period.

    (On this note, I believe that quantification of uncertainty should be the standard companion of any trustworthy prediction, so it might look like a very late recognition if we made this a central focus of a “new science initiative”.)

    Just to use again my favourite example, an increase in atmospheric CO2 is likely to affect vegetation water use. Nobody really knows how vegetation is going to react in a given environment and we cannot draw from past observations, as we have never experienced elevated CO2 concentrations in the past. Clearly, the assumption that correlations between vegetation water use and environmental variables found in the past can be projected into the future is likely to be violated. I see this as an additional challenge that we have not been aware of 10-20 years ago. To quantify the increased model uncertainty resulting from this changing condition is one (difficult) thing, reducing this uncertainty by improving our understanding of the effect of CO2 on vegetation is an entirely different thing, but both have to go hand in hand.


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