Bernhard Wehrli: an active retirement

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Cover picture: Bernhard Wehrli and his ’personal technician’ ChristiCover picture: Bernhard Wehrli and his ’personal technician’ Christian Dinkel at the ’Free University of Kastanienbaum’.

In the 45 years since he began studying Chemistry at ETH Zurich, Bernhard Wehrli has been a research scientist, Head of Department and member of the Directorate at Eawag and Professor at ETH Zurich, as well as holding various other positions. Though he has now retired, he remains committed to freshwater science and sustainability.

There is no doubt that Bernhard Wehrli sought to build bridges - between students and lecturers, between disciplines, within the ETH Domain, at Eawag, and also with practice and policymaking - but these efforts were not always universally welcomed: on matters of policy, he was not afraid to articulate well-founded positions with the necessary tenacity. At the end of 2019, for example, in the context of two popular initiatives, he drew high-level criticism for publicly arguing that action was required on the issue of pesticides in water. He also sometimes disagreed with the ETH Executive Board (closure of the Institute of Science, Technology and Policy) or with Eawag management (reorganisation) and did not hesitate to state his case.

Dedication to interdisciplinary teaching and research

While certain disagreements may have been stressful, there was no shortage of successes in Wehrli’s career as a scientist and water protection expert. One example is the interdisciplinary "Green Power" project (1997-2000), in which Eawag developed principles for the certification of sustainable hydropower production which are still applicable today. Parts of the project, such as the investigation of hydropeaking downstream of hydropower plants, subsequently also influenced Swiss legislation. This was particularly gratifying for Wehrli - as was the gratitude expressed by environmental systems science students or the successful development of interdisciplinary activities at ETH Zurich, such as system practical courses or ETH Week.

Ritualised research

Wehrli is aware that success in research is relative: "Anyone who sticks their neck out too far is brought back into line by reviewers - really new ideas are rare." Often, he says, the same questions are merely investigated in more detail with new methods and new technologies, which is not wrong, but ultimately uninteresting. This is partly due to the fact that - in the imaginative chemist’s eyes -research is highly ritualised, "almost like the church".

You can only be really satisfied when your own research findings make it essential to rewrite the textbooks. As an example, Wehrli mentions the discovery that the release of dissolved phosphorus from lake sediments cannot be prevented by artificial ventilation - "It took us years to gain a better understanding of this process." Or again, the surprising finding that large amounts of methane rise to the surface of reservoirs via gas bubbles and are thus emitted to the atmosphere.