Towards Smart Water Cities – opportunities arising from Smart Rain Barrels for urban drainage and water supply

In this work, the concept of the smart rain barrel (SRB) as an IoT solution for green infrastructure is presented. The SRB are real-time controlled micro-storages (200 litre) used for an advanced rainwater management. System states and high-resolution weather forecasts from the meteorological service are integrated into the control strategy to provide adequate rainwater for irrigation requirements and to reduce peak runoff in the drainage system. The integration into the smart water infrastructure and the exchange of control commands is done via LoRaWAN, a low-power radio network. For ease of development and to demonstrate the effectiveness of the SRB concept, a two-stage approach was chosen.

First, a prototype of the SRB was built, which is in operation at the university campus of Innsbruck (Austria) during the summer months since 2019. The campus area, also denoted Smart Campus, is part of a pilot project for a “Smart Water City”. This campus is used as both, demonstration object and experimental framework for smart applications in urban water management. The Smart Campus integrates water supply and urban drainage into a joint controlled system, in which natural and anthropogenic water inflows and outflows are measured in real-time. Current measurements encompass water consumptions and pressures in the distribution system, meteorological data at different locations, filling levels in the drainage system, as well as filling levels and soil moistures of decentralised stormwater retention and infiltration systems. The temporal resolution of the measurements is depending on the application between 1 and 15 minutes. By using these high-resolution measurement data, the Smart Campus is an ideal testing ground for smart applications such as the SRB.

In addition, numerical simulations were carried out to test different control strategies and to investigate the effects of a large-scale implementation of the SRBs at community level. The results show that the SRBs can significantly improve system performance (e.g. reduce potable drinking water demand and reduce the risk of flooding) despite their small storage volumes. But the results also demonstrate, that if a large number of SRBs are implemented, a coordinated control strategy to operate SRBs and urban water infrastructure is necessary to avoid a worsening of the system (e.g. generate a combined sewer overflow by simultaneous emptying the SRBs during dry weather flow).