Harvesting graywater and rainwater: Sustainable projects in the face of climate change

According to UN-Water, climate change is “first and foremost a water crisis”. Extreme weather events make our water scarcer, more polluted, and less predictable. This threatens biodiversity and access to clean drinking water and sanitation around the world. You may not feel the water crisis directly. Not yet. Because even in the driest of summers, water flows “normally” from your tap. But, especially if you have a garden, you have probably already thought about rainwater harvesting.

Even in (water)rich countries like Germany, summers are getting drier and drier. And using precious drinking water from the tap to water the garden? That’s expensive and very wasteful.

Many of our partners have realized that sustainable water management is one of the most important challenges of our time. Here we show you how sustainable hotels and vacation rentals use graywater and rainwater, and what you can do yourself.

The World in Water Stress

Quick Facts:

• According to UN-Water, 2.3 billion people currently live in countries experiencing “water stress”. This means that more freshwater is needed than is available.
• Water-stressed countries either tap their groundwater reserves or extract their freshwater from saltwater, which requires a lot of energy and resources.
• Flooding and sea-level rise can contaminate land and drinking water resources and make them too salty for agriculture.
• Many rivers are fed by glaciers, ice, and snowfields – global warming has a significant impact on these and affects many people.
• Droughts lead to forest fires. These threaten the lives of local people and animals. In addition, forest areas are lost as CO2 reservoirs. Burned soil can produce less groundwater.
• Reduced groundwater levels exacerbate water scarcity and food insecurity.
• Global water demand is increasing by 1% per year. According to the United Nations, water consumption increased sixfold between 1930 and 2000. About 70% is used by agriculture and 20% by industry.

“Sustainable water management is essential (…) Everyone has a role to play – action at the individual and household level is crucial”

– UN-Water

Rainwater harvesting: We show you three options

The simplest solution: a rain barrel

Plants love rain. Not only is soft rainwater free, but it’s also better for plants than hard tap water. The easiest way to use rainwater for your garden is with a rain barrel. The Hotel Klosterbräu in Seefeld, Tyrol, has placed several 100-liter containers on its grounds and uses the collected water for garden and balcony plantings.

Tip: The most effective way to use a rain barrel is in combination with a rain gutter, which collects roof runoff and directs it into the barrel.

Harvesting rainwater using cisterns and water basins

The Naturhotel Outside in East Tyrol already has a large natural swimming pond and a Kneipp path in the outdoor area. In addition, the next excavation in the garden will include a cistern to collect rainwater for use in the garden.

If you have a large garden to water, or if you want to use rainwater for domestic purposes (such as flushing toilets), it’s worth considering a cistern. A cistern is buried in the ground and has an inlet through the roof gutter. The water first goes through a filter and is then collected. Typically, you can draw the collected rainwater from a faucet in the garden or connect it to the domestic water system in the house.

At STURM in the Rhön Biosphere Reserve, there are two cisterns that help to sustainably manage the 20,000 square meters of gardens. Only native and climate-resistant plants have been planted, and there are many hiding places and shelters for insects and animals. Another of the hotel’s measures is to avoid sealed surfaces (for example, the STURM has a gravel parking lot instead of a paved one). According to the German Federal Environmental Agency, sealing soil leads to the loss of “important soil functions”. The most important of these are “water permeability and soil fertility”.

Cisterns and IBC containers (“grid tanks”) at the Creativhotel Luise in Erlangen, Germany, can be used not only for watering the garden and microforest but also for flushing toilets.

“Cities are particularly threatened by climate change because the heat has a more extreme effect there,” says owner Ben Förtsch. “So we planted a microforest in our backyard to create a better microclimate, more biodiversity, and better air quality.”

Underground Water Treatment

Some of our partners have even invested in sophisticated underground water treatment systems. Especially in warm climates. At the ADLER Spa Resort SICILIA in Sicily, both rainwater and graywater are treated and reused to irrigate the large garden. water reclamation and energy autonomy will be increased through further solar installations.

At the Eco Aparthotel The Dreamer’s Club on the island of Korcula, Croatia, the cistern system even provides water for washing machines and showers. Planting in the garden is deliberately limited to native (or indigenous) plants that require little water. “In this way, we not only use less water but also promote local biodiversity and support the health of our ecosystem,” says the eco-apartment hotel.

Effects of water shortage and countermeasures

Dried up rivers

As a result of climate change, rivers in many places are drying up, having low water levels, or disappearing altogether. In the drought summer, inland navigation was impossible on several European rivers.

Researchers cite two reasons for dwindling rivers:

• Climate Change
• People

One example is the Schwarza River in Lower Austria. Along the river, there are about 30 small power plants that own water rights and take water from the river, criticized the Schwarza water association a few years ago. The Schwarza also flows through the Gut Guntrams property. The sustainable accommodation is located about 60 kilometers from Vienna. The river bed of the Schwarza remains dry most of the year, the owners report.

Plants that need little water

Gut Guntrams has therefore begun to replant the riverbed with drought-resistant plants. On the estate itself, which has its own organic farm in addition to exceptional vacation accommodations, there are now a growing number of plants that can survive without water. Recently, many wild shrubs have been added, such as Rowan berries. Drip irrigation has been chosen as the form of irrigation, which is very water efficient compared to sprinkler systems.

In Gran Canaria, where our partner Casa León Royal Retreat is located, there is very little rainfall anyway. However, even the small amount of rainwater from the cistern is enough to water the garden of the 10,000 square meter property. Because of the remoteness of the Canary Islands, many endemic plants grow here. These include the Canary Island palm (Phoenix canariensis), which can grow up to 30 meters high, and various species of cactus.

Water scarcity despite rainy season

In Thailand, the weather situation is quite different. Between May and October is rainy season, where you can expect up to 24 days of rain per month. Nevertheless, the tropical country has a water problem, which is mainly related to the massive extraction of groundwater. According to the magazine “Der Spiegel”, Thailand now extracts twice as much groundwater as it did 60 years ago. “Tourism is depleting the island’s public water supply,” says the team at Keemala on Phuket. The sustainable luxury resort has an exemplary water management system that makes it 100 percent self-sufficient by collecting, filtering, and reusing both rainwater and graywater.

Plants as water filters

Another unique feature of Keemala is that special aquatic plants are grown to naturally filter and keep clean the water in the river and waterfall.

Tip: You can also use plants as pond filters in your garden. Find out which pond plants work as filters in your area. In Germany, for example, it is duckweed.

Use gray water for toilet flushing

As you probably know, the bathroom is where we use the most water. Even a modern toilet flush uses between 3 and 6 liters of water per flush, which quickly adds up to 30 liters (per person) per day. A 5-minute shower uses about 50 liters of drinking water (depending on the shower head and water pressure). For drinking, however, we only need 2 liters per day.

The use of gray water can prevent so much precious drinking water from being flushed down the toilet. At Paradiso Pure.Living on the Alpe di Siusi in South Tyrol, Italy, a special gray water system is currently being installed. In the first construction phase, the new sanitary facilities have already been equipped with additional pipes. Once the second phase is completed, the cleaned and filtered wastewater from showers and baths, known as gray water, will be used to flush toilets in the Japanese washlets.

Using the waste water from the shower to flush the toilet can save hundreds of liters of water. The Japanese TOTO toilet also ensures hygiene

The Environmental Advisory Service of Bremen, Germany, states: “Drinking water (…) is by no means available in unlimited quantities”, which is why it is important to “conserve drinking water resources”. Furthermore, the population is urged to use rainwater for gardening and toilet flushing – this could replace almost 40 percent of the drinking water in a private household (which is not even needed for this purpose in drinking water quality).

We hope we could give you some inspiration on how to save precious drinking water by using rainwater. How do you do it at home?