Die chronologische Liste zeigt aktuelle Veröffentlichungen aus dem Forschungsbetrieb der Hochschule Weihenstephan-Triesdorf. Zuständig ist das Zentrum für Forschung und Wissenstransfer (ZFW).
Green roofs play a crucial role in climate change mitigation strategies. On the one hand, they should reduce the risk of urban floods after heavy rainfalls. On the other hand, they should cool the city by evapotranspiration and avoid the formation of urban heat islands. However, concurrently most green roofs in Germany are extensive ones. They are designed as dry sites, with shallow and well-drained vegetation layers, no additional irrigation and greened with highly drought-adapted plants - mainly sedum. Indeed, during the last years a new kind of extensive green roofs – still with shallow vegetation layers – but equipped with sub-surface irrigation and voluminous retention elements as temporary water storage beneath the vegetation layer as well as greened with plants with high transpiration, were developed. But also these new kind of green roofs are facing a conflict of objectives between storm water retention and cooling performance. To solve this conflict of objectives an adaptive and sensor based water management system was developed. It consists of two main components: Irrigation management of the plants and management of storm water runoff, especially the control of the retention element. For the irrigation management a decision matrix was developed which adapts the irrigation strategy, depending if cooling performance or water retention has higher priority. Prioritization is based on thermal discomfort and rain forecast. The decision matrix uses environmental data, data of the weather forecast and information about water resources (e.g. grey water, water supply in the retention element). For management of storm water, run-off is actively controlled and the vegetation layer used as temporary water storage. In combination with a retention element, this can quadruple water retention capacity of green roofs. The amount of water stored in the green roof system – especially the retention element – is mainly controlled on basis of real-time, radar-based precipitation data.
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Heinz-Josef Schmitz,
Ivonne Jüttner,
Dr. Dieter Lohr,
Prof. Dr. Elke Meinken
Extensive green roofs are a key component of urban water management in the future. On the one hand, they should mitigate urban heat islands, for which evapotranspiration has to be maximized, and on the other hand, they are supposed to reduce the risk of urban floods after heavy precipitation events. To achieve these goals, an exact measurement of the water supply status is necessary. In arable soils as well as in organic growing media, dielectric sensors are widely common. However, there is only little knowledge about the suitability of this kind of sensors for mineral and coarse-textured substrates used for extensive green roofs. In the current research four dielectric sensors (EC-5, 10 HS, SMT 100 and Aquaflex TR) were tested using five different green roof substrates. The five substrates were filled in plastic boxes of 80 x 60 cm. Substrate height was 15 cm and the four sensors were placed at half height. Afterwards, white lupine was sown and cultivated up to a height of about 30 cm. For testing the sensors, the substrates were saturated with water and then they have been left to dry out until plants show severe signs of wilt. During dry out, the sensor signals as well as the weight of the boxes were recorded automatically every five minutes. For each substrate six consecutive drying cycles were done. With exception of the Aquaflex TR, for all sensors output signals were closely linear correlated to the weight loss and signal ranges were comparable for the six drying cycles. However, significant differences in output signals of the sensors between the five tested substrates were observed. This indicates a need for substrate specific calibrations. The relation between the output signal of the Aquaflex TR and the weight loss was not linear, but also reproducible and suitable to assess water supply status of plants.
Mehr
. Medienbeitrag,
Prof. Dr. Elke Meinken,
Heinz-Josef Schmitz
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