Rainwater utilisation in Germany: efficiency, dimensioning, hydraulic and environmental aspects

In this study, the development and performance of rainwater utilisation systems in Germany are described. Initially the operational characteristics of the different types of rainwater utilisation systems are explained. The objective of the modelling-based investigations is to quantify the effects of rainwater usage systems on the urban drainage system. On the basis of a long-term simulation of 10 years rain data, the following parameters were calculated: tank volumes, covering efficiency, drinking water savings, overflow occurrence, overflow volumes, overflow reduction, recurrence time of overflows. The water balance of a one-family house and a multi-storey building in Bochum was calculated in a case study.