Research Visit to San Diego State University: Sebastian Gnann

Bristol Cohort 3 student Sebastian Gnann was based in San Diego, California, as the global Coronavirus outbreak spread and intensified.   Sebastian had to curtail his research visit a month earlier than planned, but fortunately is back in the UK.  Read about Sebastian’s experience and reflections below.


“I just returned to the UK – one month earlier than planned. The coronavirus pandemic, perhaps the most drastic situation many of my generation have experienced in their lives, has led many countries to issue lockdowns, shut their boarders and significantly reduce the opportunity to (physically) socialise. Therefore, returning to the UK seemed to be the most sensible thing to do, given the uncertain development we’re facing.

To me this period particularly highlights the value of having a sociable cohort, a sociable office, a sociable work group, and a university (University of Bristol) and a PhD program (WISE CDT) that enable these social contacts and offer a lot of support during such a time (and in general). This also applies to San Diego State University (SDSU), where I got the impression that university administration, staff and students have been dealing very well with the current situation.

Finally, some lines on my actual research visit. I had a great time in San Diego, not only because I could swap one of the wettest Februaries on UK record with a decent amount of sunshine, but mainly because I have learned a lot and met a lot of interesting people. I am thankful that I had the opportunity to work with Dr Hilary McMillan, whose expertise in (field) hydrology added (and will add) a lot to my research and eventually to my PhD thesis. I enjoyed working in a different environment, both in a different country and in a different department (Geography as opposed to Engineering back in Bristol), which always opens your eyes a little more. I even got the chance to help with some fieldwork, which was a great experience, since my PhD is 100% desk work. Besides Hilary, I have to thank Ryoko Araki, a master student at SDSU, for all the lunchbreaks and chats. I am also very grateful to all the other people at SDSU who made this visit go very smoothly and who shaped my experience positively in many ways. ­

Most part of my work at SDSU focused on the supposedly simple question: why do certain rivers behave differently, even if the precipitation and energy they receive is mostly the same? Most hydrologists will agree that differences in river catchment attributes such as geology, soils or vegetation somehow lead to a different hydrological response (e.g. streamflow). Yet we often fail to link these catchment attributes to hydrological response we observe. This is particularly true if we look at large samples of catchments (e.g. the whole of the US). There are probably multiple causes for this and we primarily focused on the role of catchment attributes with the following general hypothesis: many of the currently used catchment attributes do not contain the relevant information, but if we dig deeper (into the literature) we can find catchment attributes that are relevant. And so I started to read a lot of (often old) literature about different regions in the US and by discussing my findings with Hilary we managed to indeed find more and more evidence supporting our hypothesis. These findings will be useful to shed some more light on baseflow generation processes at the catchment scale, my overall PhD topic.

As a second project, we started to work on an open source toolbox for hydrological signatures. A hydrological signature is a metric describing some aspect of hydrological behaviour. One example is the baseflow index (BFI), the ratio between baseflow and total streamflow, which is often used to describe whether a river is groundwater dominated or not. A toolbox will help people to easily use a variety of hydrological signatures in a standardised way which will be useful to many hydrologists and will help to enhance reproducibility.

The fieldwork we did aimed at measuring river velocity and discharge with the help of a video camera, a rather modern technology whose reliability is still to be explored. While this wasn’t directly related to my PhD, it was nevertheless a useful experience and a fun distraction from the office.

So, while this trip might have ended too soon, I took a lot away from it. And since work meetings and socialisation will go online during the next weeks or probably months, working with both my Bristol and my San Diego colleagues won’t even be that different – except for the time difference and probably more clouds when I look out of my window.

Thanks again to the WISE CDT, my supervisors in Bristol (Dr Nicholas Howden and Dr Ross Woods) and in San Diego (Dr Hilary McMillan), and everybody else who gave me the opportunity to go on a research visit to San Diego. They have all been contributing to create a friendly and supportive environment, which is particularly important in times like these.”