The total amount of water on our planet, in theory, has remained the same since the formation of the Earth. It is possible that the glass of water you drank earlier contains particles that once flowed down the Ganges River, passed through a dinosaur’s digestive system, or even cooled a nuclear reactor. Of course, before your thirst was quenched, this water evaporated and fell like rain millions of times.
Water can be polluted or misused, but never created or destroyed. According to a UNESCO study, it is estimated that the Earth contains around 1,386 million cubic kilometers of water. However, 97.5% of this amount is salt water and only 2.5% is fresh water. Of this fresh water, most (68.7%) takes the form of permanent ice and snow in the Antarctic, Arctic, and mountainous regions. Another 29.9% exists as groundwater. Ultimately, only 0.26% of the total amount of fresh water on Earth is available in lakes, reservoirs, and river basins, where it is easily accessible for the world’s economic and vital needs. With the population constantly increasing, especially in urban areas, several countries have already had serious problems in providing the necessary amount of drinking water to their populations.
At the same time, a significant amount of drinking water is known to be lost due to leakage, waste, and misuse. In domestic households, studies show that between 40% and 50% of water consumption does not have to be suitable for human consumption. This includes water used for toileting, irrigating, cleaning, and even laundry. Of course, this does not mean that dirty or contaminated water should be used. Rather, rainwater, for example, can be used for such applications. It is an economical and responsible socio-environmental alternative that governments should increasingly promote. Countries like Australia are already highly developed in terms of rainwater use, but for many other countries this is not yet a reality. To include this technology in future projects, architects need to consider a few things.
In addition to reducing the consumption of drinking water, collecting rainwater does not overload the urban drainage infrastructure in case of heavy rains. The system is quite simple. The catchment area is generally the slab or roof of the building, but the water can also be drawn from other surfaces, such as a street or plaza. From there, the water is channeled through gutters and pipes to the reservoir. The tank is the most expensive component of the entire system and its correct sizing is essential so that rainwater can be used satisfactorily without wasting resources and space.