Winner Wetskills The Netherlands 2017: Flushing fish – case for Waternet



“A solution as simple as innovative. Why did we not think of this before? “With these words, Henk Ovink, Dutch envoy of international water affairs, announced the winner of Wetskills Challenge the Netherlands 2017 during the plenary concluding session of the AIWW. The group of Thijs Lieverse invented a new fish migration system for Waternet. The concept: “See the poldersystem as a toilet. If the water in the sink (polder) reaches a certain level by rainfall, a signal is given and a passage through which fish can swim all be opened.”


Thijs and his team members Asandiso Mbewu (South Africa), Radwa Elzeiny (Egypt) and Jelle Dijkema (Netherlands) received their award from Nomvula Mokonyane, the South African Minister for Water and Sanitation. Thijs: “I did not expect this. I just started my third year of Civil Engineering at University of Twente and my interest is mainly in coastal defense, so this was totally different. Very nice to see how to reach an enthusiastic team so much in a two-week challenge.”


A sustainable fishing pass
Thijs: “Fish want to migrate because they are looking for food, shelters or for a mating partner, but our polding system often makes this impossible. A fishing passage that uses Waternet a lot a kind of passage with a permanent opening, through which the water flows continuously with small turns over a ‘staircase’. The problem with this though is that you are continuously losing water. Pumping water back into the system to keep the right level, takes a lot of energy and it also causes too many nutrients to be pumped into the system (eutrophication), which disrupts the ecology.”


Rain as a solution
“Our idea was to develop an event triggered system, so that only under certain conditions there is an opening through which the fish can swim. And what is a typical recurring event in Holland? Rain! The idea is to raise the water level in the polder by rainfall to a certain level. In the same way as the water in the toilet also raises. At some point, the system gets the signal ‘full’. At that moment the passage for fish opens. Because we have large polders, the passages can stay open for a few days. As a result, fish can migrate most of the time.”


Talk to the outside world
After Thijs pitched the solution one more time for a big audience, Henk Ovink encouraged all Wetskills participants to keep going and to also talk to the world outside, outside of the waterworld. “My prime minister, Mark Rutte, wants to put water issues on the agenda. He is keen on making this happen, with the young and old, with the Dutch and with the rest of the world. Wetskills stands fort that ambition.”

Text: translation from this article on H2O waternetwerk.

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