Rainwater Harvesting

Heutzutage ist Wasser der wichtigsten Rohstoff der Welt, aber in vielen Länder wird das Regenwasser verschwendet, obwohl es ein Mangel an Süßwasser gibt. Warum verwenden wir diese frei geliefert Süßwasser Quelle nicht? In Großbritanien ist Regenwassernutzung eine neue Idee um diesen Mangel zu überwinden, aber in Deutschland gibt es bereits viele erfolgreiche Beispiele für Regenwassernutzung. Großbritannien kann hier viele Anregungen für diese umweltfreundliche Technologie finden.

A valuable commodity

What’s the most valuable commodity on Earth? Coal? Oil? Gold? Well it’s none of these. It is in fact something that we each come into contact with every single day of our lives. Water. Only 3% of the world’s water is freshwater and with two thirds of that frozen in the poles, it’s no surprise that ‘water availability’ is becoming such a hot topic.

“Water, Water, everywhere,

nor any drop to drink”

                                                    Samuel Taylor Coleridge

Infographic showing the basic layout on a rainwater harvesting system

Copyright: lowenergyhouse.com

There are numerous ways people are coming up with to try and help increase water availability e.g. desalination projects and water re-use schemes. There is however an ancient technology that had faded away in many parts of the world with the introduction of reticulated water supplies. That is of course rainwater harvesting!

The simple act of collecting the rain that falls; filtering and storing it; and using it instead of the mains water is a simple, affective and sustainable way to lower our mains water demand by up to 80%. So why isn’t it more common?

Rainwater harvesting across Europe

There is a big difference in what is known about rainwater harvesting across Europe and the world. In many rural regions and lesser developed countries across the world, rainwater is the main or only source of freshwater available to them and thus rainwater harvesting is essential for their everyday needs. However, in the urban and more economically developed regions of the world, there is a reliance on the reticulated water supply thus letting all the rainwater drain away into the sewers. In today’s water scarce climate, rainwater harvesting is being considered as a viable option to lessen the demand on the mains water supply. But what do people think about using rainwater for their daily needs?

A study was conducted to ascertain how perceptions changed between using rainwater at home and in public places.

Using rainwater in the home

In the UK, only 51% of the population had ever heard of using rainwater in their homes, be it for watering the plants, flushing the toilet or for cleaning the car. This lack of awareness is one of the key reasons why rainwater harvesting has not been widely adopted, as there is clearly a demand for it with 94% of those asked, saying that they would be happy to use rainwater for non-potable (non-drinking) purposes.

The other main reason that it isn’t a widely used technology is the cost of having a rainwater harvesting system installed. In the UK, there is no financial assistance in place to help people fund a rainwater harvesting system. However, in many German cities, there is an annual rainwater drainage fee (€0.5-2/m2/year) which is waived if rainwater runoff is retained or returned to the ground. This coupled with grants and subsidies to construct rainwater tanks and seepage wells ensures that there is a financial benefit to installing a domestic rainwater harvesting system, thus increasing the uptake of such technologies.

The final reservation people had about using rainwater in their homes was the potential impact it could have on their health if it were to be ingested. It was perceived to be a lot less risky to use rainwater for things that had no chance for it to be ingested such as flushing the toilet or mopping the floor, rather than showering or washing the dishes.

Rainwater harvesting in public places

The same health concerns were raised when asked about using rainwater in the public domain; however people perceived it a lot less risky to health when using rainwater for the same non-potable reasons as if in the home (e.g. flushing toilets).

The financial issues were not at all raised for rainwater harvesting in public places. The major difference being that in the UK public sector, rainwater harvesting systems have a financial structure supporting its uptake in the form of tax incentives for those that have them installed. This has helped firms lower their carbon footprint whilst also minimising their costs due to their lower taxes. The same can be seen in Germany, with the largest system saving approximately 100,000m3 of drinking water per year at Frankfurt Airport. The harvested rainwater is mainly used for toilet flushing, watering plants and cleaning the air conditioning system.

Rainwater Harvesting is also undertaken at the Technical University of Darmstadt. The university has a colossal rainwater harvesting system. The water is used for toilet flushing and it is supplied to the University’s laboratories for cooling and cleaning purposes. This has reduced the demand on drinking water by 80%, amounting to a saving of 80,000m3 of drinking water per year.


These are just two examples of demand on drinking water being dramatically reduced with the introduction of rainwater harvesting. With more awareness about rainwater harvesting and a financial incentive to install such a system, big savings can be made across the world on the demand on freshwater. With an average of 30% of a households water being flushed away down the toilet, using rainwater for this one purpose alone could have a huge effect on our demand for freshwater and hopefully will start to help lessen our water scarcity.

Rainwater harvesting is just one of many examples in which Germany leads the way in Europe with sustainable/green technologies that the UK has to try and emulate if we are to curb the effects of human-induced climate change.

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