The Grand Challengers Podcast Episode #69

Switzerland’s sponge city network, breaking silos and the trouble with a “spongy” word

Guest: Silvia Oppliger

August 25th, 2026

Overview

Switzerland spent most of a century getting rainwater out of sight as quickly as possible. Reversing that is less a technical problem than an organisational one, and Silvia Oppliger has spent three years working on the organisational half.

An environmental engineer trained at EPFL, she began in wastewater almost by accident, applying to anything with the word “water” in the job description. She spent years at an engineering consultancy and helped write the national guidance on managing wastewater and rainwater in wet weather. That work is also what showed her the limits of her own profession. Rules written by water people, for water people, only reach projects at the permit stage, long after the decisions that matter have been made.

In 2022 she took over the Swiss Water Association’s sponge city initiative on two criteria: a network outside the water sector, and more than one national language. Since then she has assembled a network spanning federal offices, cantons, municipalities, universities, the professional associations for engineers, architects, landscape architects and spatial planners, and the insurance sector, including the cantonal building insurers and the Mobiliar cooperative.

The conversation moves through the specifics that make Swiss practice unusual. Article 7 of the Water Protection Act and its narrow focus on infiltration. The awkward legal grey zone where cantonal street laws meet green infrastructure. The regional split where soil expertise flows in from France and water engineering from Germany. And the property boundary, which Silvia names as the single line where the biggest gains are still locked up.

Underneath it runs a quieter thread about language. She grew up with three, learned to hold her own in a room of 70 male engineers at 27, and now argues that the profession’s next task is learning a fourth one: architect.

Episode Teaser

Teaser caption…

Biography

“… The main thing I do is to put people together and try to help them understand each other…”

Silvia Oppliger studied environmental engineering and science at EPFL, drawn to a discipline that let her keep both the mathematics and the sociology rather than choosing between them. Water followed, less by design than by persistence. She applied for every job description with the word “water” in it and ended up in wastewater, where she discovered that urban systems put people at the centre of the work in a way that river restoration does not. From 2013 she worked at Hunziker Betatech in Bern as a project manager in urban drainage, and contributed to the national VSA guidance on managing wastewater and rainwater in wet weather, the document that now underpins sustainable urban drainage practice across Switzerland. Since February 2022 she has led the VSA’s sponge city initiative, which began as a three-year strategic programme and has since continued as a permanent national network.

She describes herself as a systems connector rather than a technical specialist, and the description is accurate about where her effect lies. Her network spans three levels of governance alongside the professional associations for engineers, architects, landscape architects and spatial planners, the cantonal building insurers and the Mobiliar cooperative. Under her coordination the programme has run national exchange events, six webinars and around 80 presentations, reached more than 800 experts, launched the sponge-city.info platform in German, French and partly Italian, and established a professional certification course built around cross-disciplinary literacy rather than technical depth. Her current preoccupation is retrofitting existing neighbourhoods, where municipalities have the least regulatory reach, and closing what she calls the language gap between water professionals and the architects who shape sites first. She lives in Bern with her family.

Quick Summary & Highlights

  • Ninety-five per cent of the innovation is not technological at all: Silvia’s definition of innovation puts almost all of it into how people work together. The techniques for holding rainwater where it falls are largely known. What is missing is the way disciplines and administrations organise themselves around them.
  • Twenty-six cantons in Switzerland means twenty-six different water regulations: Water is regulated cantonally rather than federally in Switzerland. When a national working group tried to write one guidance document, cantons asked for their own footnotes on a single table. Four survived. Whether all 26 apply it the same way is another question.
  • Medium-sized municipalities are quietly outrunning the big Swiss cities: Large administrations have the expertise but also the silos, so good projects stay isolated. Very small ones lack the capacity entirely. The municipalities moving fastest have one department and one willing politician covering water, green space and planning together.
  • Water professionals need to learn “architect” as a language: Engineers lead with performance and compliance. Architects lead with what a place looks and feels like. Silvia argues the technical language simply does not land, and that being heard means speaking the other discipline’s terms rather than translating into your own.

Resources Related to the Episode

Key research and publications

Tools, methods and context

Cultural, fun and travel references

Episode Chapters

(Chapters are embedded in the episode for quick access, click this to expand and view all chapters and time stamps)
  • 0:00 Intro
  • 1:59 Guest Intro & The Polyglot
  • 8:19 An environmental engineer who connects people
  • 13:54 Regulations and unifying 26 Cantons in Switzerland
  • 15:50 The road to National Sponge Cities Coordinator
  • 21:03 Terminology Discussion and Swiss Sponge City History
  • 26:05 The Swiss Sponge Cities Network
  • 33:46 Swiss Public and Private Water Management
  • 37:16 National differences in priorities and silos
  • 45:38 Communication and Knowledge Exchange Strategies
  • 50:57 Reflecting on the outputs of the first three years
  • 1:00:32 Where the Sponge Cities Network is heading
  • 1:06:35 Silvia’s Future Plans
  • 1:07:42 Q&A Start
  • 1:08:05 What does innovation mean to you?
  • 1:09:12 Key moment, event, person
  • 1:12:31 Time Management
  • 1:15:59 Favourite childhood memory
  • 1:17:10 Biggest challenge to date
  • 1:20:42 Advice for young professionals
  • 1:22:27 What would you most like to be remembered for?
  • 1:23:24 Where can people find you?
  • 1:24:13 Final Message
  • 1:24:37 Outro

Connect with Silvia Oppliger

Related Episodes

Episode #9 – Megan A. Farrelly
Don’t forget the social – experiments in urban water and energy transitions
(Related Topics: urban water governance, water sensitive urban design)
Episode #26 – Manuel Fischer
The Good, the Bad, and the Socio-Political – can science really support collaborative policymaking?
(Related Topics: collaboration, interdisciplinary, socio-ecological systems, Switzerland)
Episode #29 – Katrin Pakizer
Grassroots movements, policy instruments and timing for transforming water, biodiversity and underground management
(Related Topics: policymaking, coordination, society, Switzerland)
Episode #30 – Tobias Baur
From tropical Singapore to Europe – the “ABC Waters” of sponge cities and climate adaptive design
(Related Topics: sponge cities, collaborative planning, Switzerland)

Credits