Rainwater Collection

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Rainwater Collection

Rainwater collection in today’s Smart Cities

Rainwater collection is becoming a key part of making cities smarter and more sustainable. It helps cities use water more efficiently, reduce the pressure on public water supplies, and even stops flooding when it rains really hard. Imagine catching rainwater to water plants, clean streets, or flush toilets instead of always using treated drinking water. That’s what many cities are starting to do. Furthermore, by using smart design and natural solutions, cities can become more self-sufficient, environmentally friendly, and ready for climate change.

Rainwater harvesting helps cities become more resilient, especially when challenged by increasing droughts or major rainstorms as a result of climate change. It lets cities store water locally and reduces the chance of both floods and water shortages. This supports important goals like the UN’s Sustainable Development Goal 11 (Sustainable Cities and Communities) and Goal 6 (Clean Water and Sanitation) under the UN Agenda 2030s, as well as the Paris Agreement on climate change.

Why is water so precious?

Water is essential for life on Earth – no living organism can survive without it. Although Earth looks blue from space, only about 2.5% of all the water on Earth is freshwater, and most of that is locked up in glaciers or deep underground. Less than 1% of freshwater is easy to get to in rivers, lakes, or shallow groundwater for drinking, farming, and daily use1Unicef, “Water scarcity.” 2020.  https://www.unicef.org/wash/water-scarcity. As the global population grows and climate change increases the likelihood of droughts and water shortages, the demand for clean water is going up faster than nature can replenish it. According to the United Nations, by 2025, around 50% of the world’s population might live in areas where clean water is scarce2Unicef, 2020.

When communities don’t have enough water, things get tough. It can lead to the spread of diseases like cholera and dysentery, especially where sanitation is poor. Food production declines because crops and livestock depend on a regular water supply, leading to hunger and rising food prices. Water scarcity can also strain economies, reduce job opportunities in farming and industry, and even spark conflict between regions or countries competing for shared water sources3Madalen Howard, “8 things you need to know about water scarcity.” World Wildlife Fund. 2025. https://www.worldwildlife.org/stories/water-scarcity-8-facts-you-need-to-know.

What is rainwater harvesting?

Rainwater harvesting is simple. It’s about collecting and storing rainwater that falls on rooftops or open areas instead of letting it run off and go to waste. You can use this water for non-drinking purposes like gardening, washing, or even refilling groundwater. It’s a simple, eco-friendly, and cost-effective way to save water, rely less on city water supplies, and help manage water shortages, especially in cities4Gaurav Mishra, “How to Take Care of Furniture During Rains: Expert Tips for Monsoon Season Protection.” 2024. https://gharpedia.com/blog/monsoon-care-tips-for-furniture-and-furnishings/.

Why are cities important in rainwater harvesting?

Cities are growing fast, and that means more people need water. At the same time, climate change is making the weather more unpredictable, with more droughts and heavy rainstorms. Cities need better ways to handle water, and rainwater harvesting is a big part of that. Urban industrial and domestic water demand is expected to increase by 50-80% over the next thirty years, and climate change is making water resource availability unpredictable. Instead of just rushing rainwater away to prevent floods, cities can collect and use it to help solve water shortages5Xiande Hu, Fenfei Gu, “Urban rainwater resource utilization: A sustainable environmental impact assessment using life cycle assessment (LCA) and water balance model.” Desalination and Water Treatment, Volume 322, 2025, 101094, ISSN 1944-3986, https://doi.org/10.1016/j.dwt.2025.101094.

How is rainwater harvested?

To catch rainwater, you only need a few key things:

  • A way to catch the rain: Usually, this is your roof with rain gutters.
  • A storage tank: This can be an underground tank or a barrel on the ground. Tanks can be made of plastic, concrete, or metal.
  • Filters: To clean the water before it goes into the tank, so you don’t get leaves and other stuff in your stored water.
  • A way to use the water: You can use gravity to let the water flow through pipes, or for bigger systems, you might need a pump.

Regularly cleaning the gutters, checking filters, and inspecting the tank are important for keeping the system working well.

FIG. 1: Rainwater harvesting6Huta Raval, “Rainwater Harvesting| A Sustainable Solution at Your Doorstep!”. September 27, 2024.  https://gharpedia.com/blog/rainwater-harvesting-solutions/

Collecting rainwater has lots of benefits. It saves water by using it for plants or toilets. It helps stop floods by easing pressure on drains and even cleans water by keeping dirt out of rivers. This is great for the environment and lowers water treatment costs. Cities collect rainwater in different ways, like using public tanks or rooftop systems. These methods manage rainwater, reduce drain overflow, and improve water quality7Nola.com, “Green roofs and public water plazas help the Dutch manage”, YouTube. March 7, 2020. https://youtu.be/rfOAspl6uaM?si=W1SdFlXt5XfwX05z.

Learn more about how to collect rainwater and calculate how much water you can collect yearly by watching this video:

In cities, both citizens and local authorities can help with rainwater collection:

 Citizens Can:

Authorities Can:

  • Include rainwater harvesting systems in building regulations and offer incentives or subsidies for installing them in homes and businesses.
  • Invest in large-scale infrastructure, such as underground storage tanks, green roofs, permeable pavement or natural infrastructure (urban stream/river, forests, wetlands) to capture and manage stormwater.
  • Incorporate smart water management systems to monitor and optimise rainwater collection citywide.
  • Run public education campaigns to raise awareness of water-saving practices.

What are the advantages of rainwater collection? 

FIG. 2: Advantages of rainwater capture systems9Geeks for Geeks, “Benefits of Rainwater Harvesting”. No date. https://media.geeksforgeeks.org/wp-content/uploads/20231108120733/Benefits-of-Rainwater-Harvesting.png

Rainwater harvesting has many environmental, economic and social advantages10Alan Fewkes, “Expert Blog: Benefits and risks of rainwater harvesting”. July 8, 2022. https://www.ntu.ac.uk/about-us/news/news-articles/2022/07/expert-blog-benefits-and-risks-of-rainwater-harvesting access: January 24th 2025:

  • Saves Water: It reduces the need to take water from rivers, lakes, and groundwater.
  • Reduces Floods: It lessens the amount of water going into drains all at once, which can cause flooding.
  • Environmentally Friendly: It helps protect natural water sources and ecosystems.
  • Saves Money: It can lower your water bills.
  • Good for Dry Times: Stored rainwater can be used when there’s not much rain.
  • Simple Setup: Rainwater harvesting systems are fairly simple to build.

What are the disadvantages of rainwater collection?

There are some potential environmental, health and economic problems if not properly managed:

  • Health Risks: If the water isn’t filtered well, it could carry germs from bird droppings or other things on the roof and make you sick. This is especially a concern if the water is used for drinking.
  • Cost: Setting up and maintaining a rainwater harvesting system can be expensive.
  • Ecosystem Impact: If too much rainwater is collected, it could affect the natural water cycle and harm local plants and animals.

Real world examples: 

Germany: In Germany, rainwater collection is a common practice. More than 1.8 million households use it for everyday tasks like watering plants and washing cars11Helmuth Ziegler, “Raindrops falling in my reservoir – Harvesting Rain in Germany and the EU”. No date. https://www.smartcitiesdive.com/ex/sustainablecitiescollective/raindrops-falling-my-reservoirharvesting-rain-germany-and-eu/16781/ access: February 24th 2025, and by 2024 over 60,000 rainwater tanks had been installed across the country12Fraport AG, “Environmental Aspects”, No date. https://www.fraport.com/en/sustainability/environment-and-climate/environmentalaspects.html. Even large facilities, such as airports, treat and reuse rainwater to cut down on water consumption. This approach reflects Germany’s goal of storing and using water locally in order to protect the natural water cycle13Federal Ministry for the Environment, Climate Action, and Nuclear Safety, “Background Information on the National Water Strategy”. No date. https://www.bmuv.de/en/topics/water-management/national-water-strategy/backgroundinformation-on-the-national-water-strategy access: January 24th 2025.

The Maldives: These islands have very little freshwater, so rainwater harvesting is super important, especially as there are no rivers or lakes to store and collect rainwater from. As such, the government encourages rainwater harvesting to deal with the lack of freshwater. The Maldives is an archipelago of more than 1000 low-lying islands, which means it’s highly vulnerable to rising sea levels.

FIG. 3: A Typical Rainwater Harvesting Installation in the Maldives14Ahmed Zaan Hussain, “ The Evolution of Water Resources in the Maldives”, March 6, 2024. https://www.linkedin.com/pulse/evolution-water-resources-maldives-ahmed-zaanhussain-t1ezc access: January 24th 2025

Rainwater harvesting is a smart way to save water, cut bills, and protect the environment. It reduces pressure on rivers and groundwater, prevents flooding and erosion, and supports farming during dry spells. While setup costs and health risks from poor filtration remain challenges, examples from Germany and the Maldives show its value. In the long run, rainwater harvesting strengthens water security and offers a sustainable solution to global water challenges.

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These articles have been reviewed using AI in order to align the style and length of each article. The research and content are original to the authors noted.

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