The natural cycle of water has been modified and adapted to the urban population needs. This humankind intervention has led to environmental problems within cities that are being intensified by climate change.
During and after an episode of rain or storm, excess rainwater is directly conducted to water treatment plants or rivers nearby through conventional sewerage systems. The emerging concept of “Sponge City” seeks to optimize the usage of this essential resource, by designing an urban water system that gets closer to the natural cycle of water. The system balances events of water excess (storms, rainwater) with events of lack of water by allowing the soil and natural aquatic reservoirs, like lakes, ponds or green roofs, to absorb and naturally store it.
The six-word principle for sustainable water management is: Infiltrate, detain, store, cleanse, use and drain.
The community, the environment and the local government get benefited. Environmentally, this bioretention infrastructure design contributes to cooling down the temperatures of the area due to the evaporation of water, "improving biodiversity, ecological resilience"  and the lives of the inhabitants. The presence of more green spaces contributes to reducing the emissions of Carbon Dioxide.
As a social benefit, the creation of green areas within cities can also reduce crime. Better and greener amenities for the public promote community spirit. Available data about the benefits in the long-term is still limited. Water treatment plant costs are potentially reduced.
The role of IoT
Implementing Green Infrastructures into urbanized areas is a complex process. The provision of data about the success and benefits of sponge cities is crucial to "increase the confidence of decision-makers"  and community engagement.
Firstly, by mapping vulnerable areas where environmental problems like floods take place on a regular basis and understand the behaviour of water, through a network of sensors that can be monitored remotely with an IoT solution. Identifying the most suited areas to retrofit also prevents local governments from misplacing budget and evaluating economic benefits.
After the implementation of Green infrastructures, technology plays a role in analysing the before-after performance, in order to broaden the limited available information about good practices and create a guideline for future projects. As mentioned in a recently-published paper about barriers for the implementation of Green Infrastructures, “insufficient evidence of cost and performance due to the absence of monitoring data has resulted in industry professionals doubting the reliability of GI.” 
IoT can also be used to retrofit and manage active components of a complex and reactive smart water system. Sensors can gather information, cloud systems calculate optimal water runoffs and smart active components change the behavior of the system optimizing water flow and distribution depending on the situation in the whole network.
Embever wants to contribute to this initiative and is currently in search of new projects or challenges in the Water and Environmental Engineering field about reinventing urban water systems. We provide support in data collection and transmission to provide reliability to projects.
Li, Lei & Collins, Alexandra & Cheshmehzangi, Ali & Chan, Faith. (2020). Identifying enablers and barriers to the implementation of the Green Infrastructure for urban flood management: A comparative analysis of the UK and China. Urban Forestry & Urban Greening. 10.1016/j.ufug.2020.126770.
Lashford, C., Rubinato, M., Cai, Y., Hou, J., Abolfathi, S., Coupe, S., ... & Tait, S. (2019). SuDS & sponge cities: a comparative analysis of the implementation of pluvial flood management in the UK and China. Sustainability, 11(1), 213.