Securing a reliable water source posed one of the foremost challenges when establishing our institute. In the Czech Republic, the abundance of underground water is typically within easy reach, making wells a common solution for water procurement in rural areas. Unfortunately, our institute’s location posed a unique challenge; we found ourselves adjacent to a chasm, implying that the underground water source lay at depths exceeding 70 meters. Given the substantial energy required for drawing water from such depths, we opted for a more sustainable alternative—rainwater harvesting.
Rainwater collection is a standard practice in earthship design, primarily achieved by capturing water from the building’s roof. However, our building is enveloped by soil on its roof, prompting us to gather rainwater from the roof of an adjacent wooden cabin.
The surface area of the cabin’s roof measures approximately 22 square meters. Considering an average annual rainfall of around 500 millimeters per square meter in our geographical location, this equates to 11 cubic meters of water per year. In practice, we manage to collect about 80-90% of the water that falls on the roof, factoring in some inevitable losses. It’s essential to note that during pollen-heavy spring months, water collection becomes impossible, as the pollen can contaminate the water stored in tanks. Our realistic estimate is that we typically have access to around 30 liters of water per day.
The following sections detail our water collection, purification, and storage system. We briefly touch on our water distribution system, which closely resembles standard household water systems.
In the first step, rainwater is collected by gutters and directed to a surface tank through a coarse-grained filter. This tank serves as a settling basin where the water can settle, and it also provides a safeguard for discharging any impurities that could potentially spoil the stored water. By opening valve E, water can flow from this tank into the storage tank, passing through three water filters with progressively finer granules. The force of gravity is sufficient to move the water through the filters, eliminating the need for an additional pump. To distribute water throughout the institute, we employ the conventional method of a water pump and pressure tank. Throughout years of operation, we have consistently enjoyed good water quality, aided by the fact that the underground storage tank remains shielded from sunlight, ensuring a stable, lower temperature. Periodically, we add a small amount of chlorine to the tank. Maintenance primarily involves the surface tank, which we drain completely once a year and clean using a brush and hydrogen peroxide.