Water has been described as a finite resource. I’m talking about all water – not fresh drinkin water.
I understand that there are various things that water goes through to be recirculated through the environment, such as being absorbed by the sun and there is a cycle. But how can this lead to water being a finite resource? Are there other ‘destructive’ processes involving water that means it will be lost forever?
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It won’t run out in the same way that e.g. fossil fuels will run out. With fossil fuel, there is a limited amount on Earth, and when we use it, it disappears. The fuel is turned into something else, typically carbon dioxide and water. And that carbon dioxide and water isn’t going to turn back into fuel by itself, or by some process that’s always going on on Earth. Technically, over very long time periods, new fuel could be generated by plants and animals decomposing, but that will take millions of years. So, fossil fuels exist on Earth in a limited supply, and if we ever use them all up, there won’t be any more of it.
Water, on the other hand, exists in a cycle. When you use water, you’re not permanently using it up and turning it into something else. For instance, say you use water to give to your plants. Some of the water evaporates soon after you give it, either from the soil or from the leaves of the plant. That water vapor is returned to the water cycle immediately. E.g. it may rise up in the atmosphere, form into clouds, rain down somewhere, flow into a river, and people can then harness water from that river and use it again. Or maybe the water flows into the ocean, where it becomes salty and not usable, but then the water in the ocean evaporates too and can rain down as fresh water again.
Some of the water you gave to your plants will be “locked up” in the plant for a while, inside the plant’s cells. But then when the plant dies, the cells break and the water can come out again and be returned to the water cycle.
In this way, water will never truly run out, because it can keep going around in the water cycle.
However, what can happen is that too many people are using water at the same time. Because, while somebody is using water, it is temporarily removed from the water cycle. It’s a bit like if you live in a housing community that has a bike share program. Say there are 100 bikes that people can use freely. These bikes will never truly run out, as people will return them after use. However, if 100 people are each using a bike at the same time, then there are no bikes at that moment for anyone else to use. That may be okay if it doesn’t happen too often. But now suppose that there are always at least 150 people wanting to use a bike at the same time. As soon as one is returned, it immediately gets snatched up again. This means there are always at least 50 people who need a bike but don’t have access to one. The same thing can happen with water: if the demand for water is greater than the supply (in some location), then there will continuously be a shortage of water, even though water is still going around the cycle and being continuously reused.
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