What Happens to the Water After It Rains?
In our modern world, people get used to having things handed to them on a plate. They don’t need think about where the resources they consume come from, what happens to them after they have finished with them, or what the cost of harvesting or creating them was. This is especially true when we are talking about water, and even more true in first world, developed countries. The majority of people on the planet are able to turn on the tap and have clean water come out. Then they use the water, and watch it vanish down the drain – never to think of it again. But how does that water actually reach the tap, and what happens to it after it has been used?
Basically, all water is at some point in a process that we call the water cycle. The water cycle is defined by the USGS (US Geological Survey) as “the existence and movement of water on, in, and above the Earth”[sc:1]. All water goes through this cycle, which involves precipitation (rain, snow, hail, etc…), flow of water (usually towards the ocean or other major water bodies), evaporation, and condensation (cloud formation)[sc:2]. Around 97% of earth’s water is stored in the ocean, so in the end, most rainwater returns here, either through rainfall itself or through rivers, streams, and underground flows[sc:3].
How is water so readily available for use?
But back to our original question. To begin, let’s look at how water goes from raindrops about to meet the ground, to clean, running water coming from our taps. When water hits the ground, there are a number of things which could happen to it. It could soak into the ground, flow downhill until it reaches a river, lake, or other waterbody, or re-evaporate directly into the atmosphere (depending on climatic conditions)[sc:4].
The companies in charge of supplying water to major cities and towns then collect this water from a number of sources, including directly from the ocean, from rivers, streams, or lakes, or from underground aquifers. From the ocean, water must go through desalination plants to purify and clean it. However, this is only useful for people close to the ocean, as it is difficult to transport the amount of water that an average city needs. From rivers, lakes (purpose built or natural), and aquifers, the water must be treated before being delivered to your house to ensure that it is clean and without harmful bacteria or pathogens. Some people who aren’t connected to the mains water system (such as remote farmers) are forced to collect their own water – often in the form of rainwater or underground water. Once water has been cleaned, purified, and treated, it is then pumped to storage tanks or areas before being delivered to your bathroom or kitchen every time you turn a tap on.
What happens to the water after we have used it?
After we use water, we generally watch it go down the drain and forget about it. However, there is a long and laborious treatment process which it must undergo before it can be released into the environment again. This process removes harmful substances and makes the waste-water safe to be released into sensitive ecosystems[sc:5]. The steps involved in treating waste-water include:
- Screening, which removes large pieces of waste and things which should never have ended up in the sewers, such as condoms, nappies, and other trash.
- Primary settlement, which involves removing the rest of the solid particles by letting them settle to the bottom of large tanks.
- Biological treatment, which treats the remaining waste-water with bacteria to break down any harmful substances
- A final settlement, which removes any remaining waste particles before the treated water is released back into rivers or the ocean.
- Before the process is complete, the sludge which was removed in earlier steps must be treated with bacteria and UV light before it is safe to use as an agricultural fertilizer[sc:5].
So, as you can see, the water that you take for granted every time you turn on a tap actually requires a lot of effort and energy to transform from raindrops to tap-water. This process impacts the environment, as does the waste-water treatment process. Therefore, it is important to ensure that we limit our water usage to what we need – this could involve actions such as fixing leaky taps, taking shorter showers, or only watering the garden when it needs it.