Clear evidence of techniques used for rainwater harvesting date back to nearly 4000 years ago. However, the concept of rainwater harvesting may date back almost 6000 years in Ancient China (Che-Ani et al., 2009). It is evident that rainwater harvesting has been part of human’s history and identity. With modernization and massive urbanization, rainwater harvesting has now become part of the city’s identity. To increase efficiency, the concept of Smart Rainwater Harvesting is being introduced around leading cities. Smart Rainwater Harvesting is characterized by collecting real-time data via sensors in water sources, collection phases, storage phases, and application phases (Behdazian et al., 2018). The data is gathered in a centralized data collection unit where it is monitored and processed. The processed data is then used to make decisions and adapt to the specific circumstances.
Smart Rainwater Harvesting systems by automated methods can release stormwater prior to rainfall occurring to enlarge the water captivity levels (Behdazian et al., 2018). The main goal of rainwater harvesting systems is to collect and store rainwater during precipitation events for usage in non-drinking water applications (Pradhan & Sahoo, 2019). The smart part of this concept consists of the development of communicating assets integrated with the overall system (Xu et al., 2020). The system makes use of low-cost sensors combined with innovative communication technologies. The technological focus enables several new possibilities for the management of urban water infrastructure in a smart city framework. The performance of the system is strongly dependent on and interconnected with the quality of the weather forecast. The amount of precipitation and patterns of rainfall are integrated into the control strategy to determine discharge volume and closing time respectively (Pradhan & Sahoo, 2019).
Smart Rainwater Harvesting does not pose any different structural variants, meaning that the main concept of using data, interconnecting, and measuring harvesting methods remains the same throughout different cities. Context is a particularly important factor when considering smart rainwater harvesting, as different cities have unique needs and different means to achieve their goals. However, some variants can be distinguished based on the scale of the Smart Rainwater Harvesting. Here, we introduce micro-scale, meso-scale, and macro-scale smart rainwater harvesting systems.
Smart rainwater harvesting could occur in small-scale systems such as a simple household. For a rather small investment, a private household can have a self-sustaining smart rainwater harvesting system. A smart rainwater harvesting system in a household brings both economic and environmental benefits. These initiatives and data analysis are individually taken.
Smart rainwater harvesting could also occur in meso-scale systems such as at a neighbourhood or complex level. With some investments, a whole neighbourhood can benefit from the advantages of a smart rainwater harvesting system, making the neighbourhood water-proof and efficient.
Smart rainwater harvesting is also implemented in city-scales. Larger investments all around the city contribute to a large unified system that brings about an efficient smart rainwater harvesting system. Cities need more coordination and planning to implement the project. However, the benefits of implementing such a system on a macro scale have a larger contribution.
The current increasing urbanization demands more facilities and more resources; this creates an imbalance in demand and supply. Thus, managing resources and facilities (e.g., water supply) in urban and rural areas becomes a challenging task for the urban planner and local governing bodies. Though novel solutions have been developed to tackle some of the challenges, there are still some issues not yet addressed. For instance, most highly urbanized cities are on the verge of severe water shortage which could be worst in the near future. However, in recent years, technological advancements, and resharpened opportunities for cities to deal with a water supply and retention by adapting smart rainwater harvesting methods in their water management systems. According to Judeh et al., (2022), the most common smart rainwater harvesting phases used in the city context occurs as follows:
- Collection Phase: In this phase, all the generated runoff either from rooftop or surface will be collected.
- Storage Phase: The collected runoff will be stored in tanks (for every household) and ponds (constructed at an appropriate location in or nearby urban catchment). The excess water which exceeds the storage limit either diverted to natural stream through drainage system or routed through low impact zones to promote the ground water recharge.
- Application Phase: At this phase, this stored water can be utilized for potable and non-potable uses like domestic use, industry, gardening, landscaping, etc. The re-use of rainwater in urban catchments reduces water demand, quantity of surface runoff, flooding, and pollutants due to the storm water.
The data will be collected at every stage of rainwater harvesting and sent to a centralized data storage unit, where all collected data will be stored. Thereafter, this data will be used in two different classes for monitoring:
- Storage versus consumption and inflow versus outflow
- Inflow versus outflow and groundwater recharge.
These monitored data can then be processed at the processing unit for further analysis and used to draw meaningful output. Following this, the decision can be made for future planning by considering variation in demand and supply over time. Climate change and population growth should be incorporated when making long term strategies.
The smart rainwater harvesting market surpassed USD 296 million in 2021 and will grow at a yearly rate of 4% between 2021 and 2027(Oberarscher et al., 2019). Rising water scarcity coupled with a growing population across the globe will drive market demand. The surging consumption of water in agriculture is also likely to propel the smart rainwater harvesting market expansion. It is predicted that the Smart Rainwater Harvesting market to reach USD 328 million by 2027.
Governments across countries have started to implement RWH policies to encourage water conservation. Some countries have made it necessary for new constructions to include smart rainwater harvesting systems, such as US and Australialia (Pradhan & Sahoo, 2019).
The leading participants operating in the market include GRAF Group, Kingspan Group, Heritage Tanks, Watts Water Technologies, Inc., Innovative Water Solutions LLC, Stormsaver, Water Field Technologies Pvt. Ltd., HarvestRain, WISY AG, D&D Ecotech Services, Rainharvesting Systems Ltd., and Climate, Inc. These players are constantly focusing on expanding their product portfolio and offering innovative products.
Depending on the scale of application, the clients differ. However, it is mainly cities and regions that are investing in smart rainwater harvesting.