7 smart ideas to reuse rainwater — today and in the future

The scarcity of drinking water is already a reality in several regions of the world, including Brazil. Prolonged periods of drought, accelerated urban growth, and waste contribute to a scenario in which rethinking water usage has ceased to be a sustainable choice and has become a necessity. In this context, rainwater harvesting emerges as an intelligent, accessible strategy that is increasingly incorporated into residential, architectural, and urban projects.

Much beyond improvised solutions with buckets and barrels, collecting and reusing rainwater involves simple and efficient systems, regulated by technical standards, which can significantly reduce the consumption of treated water. Furthermore, new technologies and public policies are already being designed to expand the use of this practice on a large scale in the cities of the future.

Next, discover seven ways to reuse rainwater that are already being applied today — and what is expected in the coming years.

1. Collection through gutters and storage in residential cisterns

One of the most well-known and efficient forms of reuse is the installation of gutters on the roof connected to cisterns. Rainwater flows from the roof, passes through an initial filter to catch leaves and debris, and is directed to a closed reservoir. This water can be reused for non-potable purposes.

Today, there are compact, vertical, and underground cisterns designed especially for urban homes with limited space. What is expected in the coming years is the popularization of even more automated systems, with sensors monitoring water levels, more advanced filtration, and integration with the home's plumbing systems.

2. Use of rainwater in sanitary flushes

The toilet is one of the largest consumers of water within a home. Using rainwater for this purpose is already a practice envisioned in sustainable projects and regulated by Brazilian technical standards, such as ABNT NBR 15527.

Independent plumbing systems allow rainwater to supply only the flushes, without the risk of contamination with drinking water. The trend is that new residential and commercial developments will already begin to foresee this infrastructure from the design phase, making this use increasingly common and standardized.

3. Irrigation of gardens, vegetable patches, and green areas

Irrigation is one of the most suitable uses for rainwater, given that plants do not require treated water. In homes with gardens, vegetable patches, and even on terraces with pots, reuse can drastically reduce consumption from the public network.

What has been envisioned in contemporary landscaping projects is the integration of automatic irrigation systems connected to cisterns, with controlled dripping and soil moisture sensors. Thus, rainwater is used even more rationally, avoiding waste.

4. Washing floors, cars, and outdoor areas

Another practical and already well-diffused application is the use of rainwater for cleaning yards, garages, sidewalks, and washing vehicles. These tasks consume large volumes of drinking water that could be replaced without any loss.

[caption id="6979464336c2c45528cbc828" width="736" data-alt="cleaning the floor; mob; mop" data-caption="cleaning the floor; mob; mop" data-credit="Freepik" data-source-id="68f2b8ff98f18c7f5f5e4deb" data-source-name="Disclosure"][/caption>

In the near future, the trend is that condominiums and commercial buildings will adopt collective reservoirs for this purpose, reducing condominium costs and the impact on the public supply network.

5. Green roofs and rain gardens

In addition to storage, the architecture itself can function as a reuse system. Green roofs absorb part of the rainwater, decreasing immediate runoff and allowing it to be utilized by plants and evaporated slowly.

On the other hand, rain gardens are areas designed in the soil to receive and infiltrate rainwater, helping to recharge the aquifer and preventing flooding. This solution is already implemented in urban and landscaping projects and is expected to become mandatory in new developments and public spaces in various cities.

6. Large-scale urban reuse systems

Cities around the world are already investing in infrastructure to collect, treat, and reuse rainwater in parks, urban cleaning, and irrigation of public areas. In Brazil, some municipalities are already studying policies to make reuse mandatory in public buildings and new ventures.

[caption id="68f2bb3f98f18c7f5f5fd353" width="736" data-alt="Liupanshui Minghu Wetland Park, in Guizhou, transforms wetlands into an urban park that reduces floods, improves water quality, and offers leisure opportunities to the population." data-caption="Liupanshui Minghu Wetland Park, in Guizhou, transforms wetlands into an urban park that reduces floods, improves water quality, and offers leisure opportunities to the population." data-credit="Turenscape" data-source-id="68f2b8ff98f18c7f5f5e4deb" data-source-name="Disclosure"][/caption>

What is planned involves intelligent urban reservoirs, permeable pavements, squares designed as temporary water retention areas, and separate networks for drinking and reuse water. These measures reduce flooding, relieve drainage systems, and make cities more resilient to climate change.

7. Reopening urban rivers and the renaturalization of rainwater

For decades, many cities have channeled and buried their rivers to make way for roads and buildings, transforming natural waterways into underground galleries that receive, at once, huge volumes of rainwater. The result is frequent flooding, overload on drainage systems, and loss of green areas. The reopening of these rivers — already implemented in cities like Seoul, Madrid, and some initiatives in Brazil — returns the riverbed to the surface and allows rainwater to be absorbed, slowed, and filtered naturally by the soil and vegetation.

[caption id="69794b8736c2c45528cbc838" width="736" data-alt="The project of the Municipal Park of Rio Bixiga, in São Paulo, provides for the reopening and renaturalization of the buried brook that crosses the historic neighborhood of Bela Vista." data-caption="The project of the Municipal Park of Rio Bixiga, in São Paulo, provides for the reopening and renaturalization of the buried brook that crosses the historic neighborhood of Bela Vista." data-credit="São Paulo City Hall" data-source-id="68f2b8ff98f18c7f5f5e4deb" data-source-name="Disclosure"][/caption>

In addition to reducing flooding, this solution creates linear parks, improves the urban microclimate, and transforms rainwater from a problem into a project and environmental resource. This strategy is among the main forecasts for the planning of resilient cities to climate change in the coming decades.

CASACOR Publisher is an exclusive content creator, developed by the Technology team of CASACOR based on the knowledge base of casacor.com.br. This text was edited by Yeska Coelho.