Water supply and quality

Leon is taking a shower, when suddenly he thinks of something. Where does all the water in his shower come from?? We all know that water in the tap does not appear magically - it comes from somewhere. That somewhere is called a water source. There are several types of water sources on Earth.

Freshwater that we use in our homes often comes from sources such as rivers, or lakes. These are surface water sources. Freshwater can also come from beneath the Earth’s surface - this is a groundwater source. To access that groundwater, we need a well. If you collect rainwater, that is a source of freshwater too.

But how does water from these sources end up in our homes? We can collect it ourselves directly from a stream or a well. This was the usual way of fetching water in the past, and it still is in some rural or remote areas. However, in most towns and cities water is delivered from a source to buildings through a system of pumps and pipes - a water supply system. Such systems are run by local authorities or private companies.

There are two things that define any water source: the quantity of water and the quality of that water. A good water source is the one where there is enough water to meet the needs of all the people who want to use it. Water is a renewable resource, so most water sources get refilled, for instance when it rains, or when snow melts. Sources of water that are refilled regularly are considered reliable sources. The amount of water in a source can vary, depending on the year, season, location, and usage.

If we draw more water from the source than gets refilled, the amount of water decreases, and this can lead to a water shortage. Water shortages are common in many places around the world, especially in summer, when there isn’t much rainfall. Water also has to be suitable for its purpose. Drinking water, for example, must be clean and safe - free from bacteria, parasites, and chemicals. Water used for other purposes, such as flushing toilets or laundry, doesn’t have to be as pure as drinking water.

The more polluted or contaminated water is, the lower its quality, and the fewer the things it can be used for. The quality of water in different sources varies. Surface water sources such as lakes or rivers can easily be contaminated with rubbish, or dirt. Or there might also be chemical runoff from the surrounding fields. These contaminants often make the water look cloudy, or turbid.

But even water that looks clear, is not necessarily clean or safe. Water might contain toxic metals, or microorganisms such as bacteria and viruses. These are invisible, but when consumed, they can lead to poisoning and damage human health. Rainwater, although usually pure, can become contaminated when collected or stored. Sand and gravel often filter impurities out of groundwater.

However, groundwater can become contaminated by other substances that seep through the ground, for example chemicals or toxic metals. Most contaminants can be removed from water through different processes. Modern water supply systems often have units that filter and purify water from the source. This improves its quality. Once the water is treated, it is then pumped through a system of pipes, so that it can reach your tap, toilet or shower.