Due to climate change, dry periods are becoming increasingly frequent. Spring 2025 was one of the driest since records began. Therefore, it is essential to use this scarce resource of water as effectively as possible in the future. The startup "myCistern Operations GmbH" aims to increase the effectiveness of cisterns with its system – through intelligent control and use of retention cisterns for irrigation. The German Federal Environmental Foundation (DBU) is supporting the founders with 125.000 euros.
The analysis by the German Weather Service (DWD) is clear: March 2025 will be one of the driest since measurements began in 1881. An average of just 19 liters per square meter landed in the measuring cups during the month – significantly less than during the reference periods 1961 to 1990 and 1991 to 2020, each with an average of 57 liters per square meter. At the same time, according to the DWD, there were 199 hours of sunshine – statistically, this amount is normally only expected in the summer months. Due to advancing climate change, extreme weather events of this kind will occur more frequently.
The Landshut-based startup "myCistern" offers an approach to more targeted water use. "With cisterns in gardens and on private properties, we want to save water in two ways: Firstly, the system we developed, including the associated software, controls commercially available rainwater cisterns. The program adjusts the garden irrigation depending on the cistern's fill level," says founder Georg Dornaus. The goal is the most efficient water consumption possible, so that little or, ideally, no drinking water is used for irrigation. "The system reduces the amount of irrigation when less water is available, but retains enough so that the plants still survive," says Dornaus. When more rainwater is available again, the irrigation deficits can be compensated. According to the "myCistern" founder, weather data is also incorporated into the calculations. The system also ensures that the pump does not run dry and notifies you when the filter needs to be cleaned.
In addition to traditional rainwater cisterns, the founding team is also looking at retention cisterns. These special cisterns, required by some municipalities, must be installed by homeowners so that during heavy rain, not all of the water flows directly into the sewer system – thus preventing flooding. Rainwater is temporarily stored and only gradually drained into the storm drain – an "untapped potential," says Dornaus: "Retention cisterns can also be used for irrigation. For this purpose, we have developed a closure that allows them to be used like normal cisterns during periods without heavy rain." The intelligent control system is linked to weather forecasts and "recognizes when heavy rainfall is imminent. The retention cistern then empties in time and can thus temporarily store a large amount of water." According to "myCistern," the retention cistern is worthwhile for both the municipalities and homeowners, as it saves drinking water and thus costs. To demonstrate this effect, the startup says it is collecting a wealth of data during its DBU funding period. The goal is to convince communities of the benefits of dual-use retention cisterns.
According to Franz-Peter Heidenreich, the responsible DBU (German Federal Environmental Foundation) representative, systems like the one from "myCistern" enable municipalities to prepare for extreme weather events – based on the sponge city principle. Heidenreich explains: "This involves a city's ability to absorb and store excess water like a sponge, for example, through green spaces, multifunctional areas, or intelligent retention cisterns, and then release it again, perhaps through targeted irrigation of green spaces and urban trees." In this way, cities are less affected by flooding during heavy rainfall and are better supplied with water during prolonged dry periods. Heidenreich adds: "In sponge cities with sufficient water reservoirs, parks, green spaces, and urban trees also act like natural air conditioners."
About the Green Startup Funding
With its Green Startup funding, the DBU supports young founders who develop solutions for the environment, ecology and sustainability in an innovative and economically viable way.
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