Climate stress

Near-nature hydrological cycles for 16,000 square meters of development area

A research team at Fraunhofer ISI is investigating what a near-nature hydrological cycle in an urban development might look like in the i.WET project, short for integrated water energy transition concept. The project is currently being realized in the area occupied by the Coers-Fläche in Lünen in North Rhine-Westphalia, on a former industrial estate covering almost 16,000 square meters, which is now being developed with seven residential blocks. The gray water from washbasins, bathtubs and showers is fed through a heat exchanger in order to recover the heat for other applications. This water is then collected in a reservoir together with the rainwater and used for toilet flushing — in this way, valuable water can be saved, especially during dry spells. Further rainwater is stored in three cisterns and used for watering green areas. Any gray water and rainwater accumulating beyond this runs into the core of the near-nature hydraulic circuit: a planted “green avenue,” in which the water is cleaned and retained. Here, it first seeps through a green planted soil filter, or rather a cleaning layer containing a special grain of sand. Located below this layer of soil is a channel, through which the water discharges into an open ditch and then onward into a small river. “Even when the rain is torrential, we can completely separate the rainwater from the sewerage system and ease its load,” says Dr. Thomas Hillenbrand, Head of the Water Management business unit. The vegetation in the energy avenue also ensures pleasant cool temperatures during the summer and enhances the surrounding area.