b'BLUE-GREEN ROOF SYSTEMS Phase 3a is testing two alternative watermoist and healthy without any supplythe entire dry period. When the soil recirculation mechanisms. For Roof A,or water from the cistern, whereas RoofMC approaches wilting point, and the water availability for the plants isB has required the cistern to be refilleddepending on whether sustained set based on the soil moisture content,with potable water three times.drought or sufficient rain are in the which aims to take advantage of thePhase 3b will implement a weatherweather forecast, the controltransient nature of the soil moistureforecast-based runoff control. Duringsystem decides either to supply just retention. Roof B, the water availabilitythe dry season (Figure 7) the objective isenough water to maintain consistent is set based on the water level in theto ration the amount of water suppliedsoil MC or not to supply anyBL, which was refilled weekly. So far asby the cistern to the BGR so that itwater, respectively.of August 31st, Roof A has remainedremains available for the plants duringThe forecast-based control system adjusts its operation based on the expected weather conditions during spring and fall. In the rainy season (Figure 8), the objective is to main-tain the BGR and the cistern empty to maximize rainwater detention in preparation for upcoming storms. This objective is achieved by main-taining a controlled BL rainwater runoff release rate in response to the weather forecast.CONCLUSIONS Vegetative roofs are a source-control climate adaptation strategy included in the City of Vancouvers engineered pathway for managing rainwater in private property. Experiments demonstrate that BGRs provide enhanced rainwater control that can potentially meet the plants needs for FIGURE 7: PHASE 3 - SUMMER OPERATION OF THE BGR. the entire dry season, while main-taining moderate roof temperatures, thereby mitigating UHI and fire risks. Research in Phase 3 of this research aims to demonstrate the water and thermal benefits of BGR systems in the winter to reduce the stress on urban and natural water systems, while also moderating roof tempera-tures through enhanced thermal mass and the BL cavity. Through healthy vegetation and perhaps combining BGR and BR systems with walkable pavers, the coupled water-thermal effects can promote urban biodiver-sity and livability. Integrating the BGR system with a downstream cistern enhances the water-thermal responses and the connection to the site. The relative size of the roof and the cistern is a critical design factor in the water-management effective-ness of their combined operation. Research is underway to model the coupled BGR-cistern design, thus supporting the City of Vancouvers FIGURE 8: PHASE 3 - WINTER OPERATION OF THE BGR. engineered pathway. 20 BCBEC ELEMENTSA BCBEC PUBLICATION'