Lausanne's sponge city: DL-SMTP measures how trees use rainwater
/What if every city tree had its own rainwater reservoir? That is exactly what the Impluvium tree pit is designed to deliver — a system created specifically for Lausanne's ecosystem, building on the well-known Stockholm tree pit. Instead of letting rainwater drain away or flow into the sewer, it is stored directly under the tree, in a special biochar-based substrate (TP70) that is at once load-bearing, fertile and water-retaining. During dry spells the pit supplies the tree; during heatwaves it cools the surroundings by up to 4 °Cthrough evapotranspiration. Pilot trials also show that 70 to 100 percent of micropollutants in the runoff are retained in the substrate.
But does it still work on a slope? At a Lausanne impluvium pit on a 12 percent gradient, HEIG-VD and the City of Lausanne's Service de l'eau are investigating exactly that — the case where water runs off particularly fast. Soil moisture and soil temperature are monitored using our DL-SMTP | Soil Moisture and Temperature Profile for LoRaWAN®. The project is just getting underway, with first results expected soon.
We are looking forward to the findings and will keep you posted.
More on the concept: Impluvium tree pit
