For our second post of “Talking hydrology”, we interviewed Hjalmar Laudon, professor and chair of forest landscape biogeochemistry at SLU Umeå (Sweden). We talked about past and current research in the Krycklan catchment and the usefulness of long-term datasets.
1) You have been conducting hydrological research at the Krycklan catchment (North of Sweden) since 2002. How did you keep yourself motivated and interested in the research in the Krycklan catchment?
I think that what we do is interesting, unique and fun, and a better understanding of the role of water in this catchment is very important in order to understand how climate, forestry and other human induced activities will affect our waters. The work and the focus of the projects themselves have been multidisciplinary. This has taught me many new things and made the work more exciting! I work with hydrologists and biogeochemists from all over the world, but also with forest historians, political scientists, forestry policy makers. Lately we also have seen big political changes and have pursued collaboration with stakeholders. Approaching Krycklan from all these different perspectives is very interesting! In addition, it is really inspiring to see that sometimes changes in the policies are implemented based on our findings. What also motivates me is the interaction with other scientists, especially young ones that come to Krycklan to carry out their research! They bring a different atmosphere compared to the ‘old guys’ that are just proceeding with their projects.
2) How were the long-term observations in the Krycklan catchment superior to the usual project lifespan of 3-5 years?
An obvious benefit of having a long-term monitoring station is that the measurement infrastructure is already installed. Since there is no need to set up everything with the start of a new project it is relatively easy to collect new data. A longer dataset also gives the opportunity to describe and understand long-term processes, such as age structure of the forest or the history of deposition of pollutants, and, all our measurements can be put into a climatic context. Nature is not in a steady-state condition if we assess it on a climatic time scale. So, if you make measurements for just a few years, you do not know on which long-term trajectory you are. In Krycklan, the long-term measurements have revealed a set of trends occurring simultaneously, for instance the increase of dissolved organic carbon (DOC) in stream water, the decrease of nitrate concentrations and pH in stream water, and changes in winter conditions. Of course, there are also negative sides to measuring at one location for a long period. Since we learn more about one specific site, we might be biased to the climate and biophysical characteristics of this particular site. Therefore, we must be aware of the mindset that we take from the catchments that we study, and how the dominant processes that we observed apply to other regions. Finally, resources are finite, and with every project one needs to decide which processes are most important to continue study. We cannot just add new measurements, we also have to close some down. This is the hardest part.
3) What type of funds are used to maintain the hydrological monitoring of the catchment?
The measurements in Krycklan started with funding by small research grants, and we combined bits and pieces to set up the infrastructure. In the last seven years we have received funding from the Swedish Research Council to maintain 15 monitoring sites on a standard protocol, which we of course hope will continue. Additionally, we search for project-based funding to do additional measurements or sampling and people that want to come to do a project in Krycklan usually take their own funding or grant with them.
4) Based on your experience with field work, what kind of advantages and disadvantages can be encountered while collecting data for a PhD or a post doc project?
One thing that has become clear is that while discharge measurements are fundamental to any hydrologist, they can be extremely difficult to carry out and are also highly uncertain. There is a large uncertainty in the discharge (or stage height) and the methods for calibration that we have are poor. We realized this when we calculated the biogeochemical fluxes in Krycklan and we found that sometimes there were some inaccuracies. So, even at a well-maintained site like Krycklan it is hard to get the discharge right, especially at the shoulder seasons to winter! To make it even more complicated: each stream section can behave differently, so it is difficult to extrapolate from a few measurements to another location. Another problem is that with extreme events the locations are likely to get damaged or require a new stage-discharge relation. This is part of the reason why we measure at 15 sites: at least one of the sites will probably survive during a flood.
Generally, when working with field data, more data show the complexity of the system which inevitably makes it harder to describe. We must also be aware that no data is flawless. That is why it is really good to have the experience of field work when you work with other people’s data.
5) Do you involve students (B.Sc. or M.Sc. level) in the work you do in the Krycklan catchment?
Currently we have about 20 PhD and 20 MSc students involved at the Krycklan catchment, but data are available on the web (open access), so there could be more people that work with the data that we are not aware of. As a result, we have around 100 publications per year that use Krycklan data! We do a lot of teaching both at SLU and at Umea University, and we take a lot of students out to the field site. Students usually work on topics on hydrology, forestry and atmospheric sciences, and currently we are starting two big new experiments: on the restoration of wetlands, and one on forest ditching and ditch network maintenance. 
6) What kind of advice would you give to early career scientists approaching field work? How would you encourage them and explain them the importance of experimental hydrology?
One advice I would give is to go to a site where there are good data. It is very valuable to work with good data. On the other hand, the problems and errors in the data are not found until someone starts working with the data. It is very easy to make errors, and they can be carried on for a long time until someone discovers them. That is why only through working with the data you know how to further develop the data collection. I also found that adding a historical, cultural or educational component to the research site can be a great help to further develop and better understand field measurements.
7) Have you ever wondered how experimental hydrology could evolve in the next few years? What kind of hypotheses should be tested? And what kind of groundbreaking instrumentations or methodologies are needed to improve our knowledge of hydrological processes by experimental data?
The comparison of different sites, and the investigation of specific questions at different sites is definitely one direction for future research. Currently, we have measurements and understanding at different locations, but to compare them can bring a new, deeper understanding to the hydrological system. Another challenge is the upscaling from plot to catchment scale. I think that large controlled experiments, such as artificial extreme events or the monitoring of the effects of impactful events such as forest logging on catchment scale (several 10’s of hectares) are both very important in exploring how to tackle this challenge. As for groundbreaking methodologies, I think that high-resolution LiDAR measurements which came in over the last ten years can continue to be very powerful to get a detailed overview of the landscape. Lastly, we need to integrate our understanding of different processes across the landscape; atmosphere, vegetation, soil, groundwater, surface water. This needs a big team effort and it is interdisciplinary in many ways! We need models to validate our ideas and to connect the pieces, and data from experimental sites is of course crucial for this exercise. One of the compartments that still needs attention before we can successfully make this integration is the soil compartment. Aspects as groundwater-surface water interaction across depth and the connection between deep and shallow subsurface waters still need a refined representation.
8) Do you have any other thoughts or inspiring words that you would like to share?
Come to work in Krycklan, we need you!
Thank you, Hjalmar, for your time and insights in experimental research in a long-term catchment as Krycklan!
For more info, the reader can visit the Krycklan catchment website or contact Hjalmar Laudon.
Edited by Matthias Sprenger and Giulia Zuecco
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Guest author Leonie Kiewiet is a PhD student at the University of Zurich (Switzerland). She is interested in experimental hydrology and focuses on the hillslope and catchment scale. In her PhD project, she uses a combination of tracer-based approaches and hydrometric measurements to investigate runoff generation processes and to quantify the uncertainty in source-area analyses due to spatial variability in shallow groundwater composition.
