The simplest way to collect water is by connecting gutters to barrels or water tanks. This way, water flowing from the roof will accumulate and can be used later, for example, to water garden beds. But there is an even better and more interesting way to retain water – rain gardens.
A rain garden is a specially designed green space that collects water during rainfall. It is usually a depression prepared in a specific way (lined with foil, stones) where rain-loving plants are planted.
MATERIALS
- Container
- PVC pond liner
- Drainage pipe
- Aggregate (expanded clay, dolomite aggregate 2–8 mm, or gravel)
- Coarse sand
Task Description
You can create a small, simple rain garden by your school or home under the guidance of a technical teacher. Let’s see how to do it!
Container
First, you will need a suitable container. Its size depends on the roof’s surface area. The container should cover about 3% of the drained roof area and have a depth of 0.8–0.85 m. It can be made of any solid material, such as concrete or wood, to withstand the weight of water and aggregate.
A hole should be made in the container to fit the drainage pipe (50, 80, or 100 mm). It is best to request this when purchasing or ask a school technician. The hole should be positioned 20–25 cm above the bottom.
PVC Pond Liner & Filling
Next, line the container with PVC pond liner, ensuring it adheres tightly to the walls. Under supervision, students can complete this task. Fill the bottom with a 20 cm layer of aggregate. Then, place the drainage pipe on top. Suitable aggregates include expanded clay, dolomite aggregate, or gravel.
Sand & Aggregate Mixture
Now, prepare a special sand layer. Mix sand with additives in a 3:1 ratio to help retain moisture and filter rainwater. The best additives include fine dolomite aggregate, crushed bricks, limestone aggregate, volcanic rock, opoka, iron hydroxide, and EM solutions (live bacterial cultures). These should make up at least 1/4 of the layer.
For the top 10 cm, mix fertile soil or compost with sand in a 2:3 ratio. Compact the material while filling to prevent uneven settling after rainfall.
Naturally occurring plants that thrive in periodically flooded meadows and require little maintenance include purple loosestrife, reed, valerian, iris, and manna grass.
This post was created in collaboration with the Veolia Poland Foundation and CultureLab Foundation under the honorary patronage of the City of Warsaw.