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A little or lots of water

Click the bucket to fill the tub with water.

What is a little water and what is a lot? It depends!

If you think of a bathtub compared to a swimming pool. Imagine throwing ten buckets of water in each. What does that mean for the water level in each basin? The water quantity or amount is the same but the effect depends on the size of the basin it goes into.

If the amount of water that comes in, is more than the amount that can be drained (or evaporated) out of the system in the same time or stored somewhere the water level will rise.

Think of the same bathtub again. If each time you throw in a bucket of water, the same bucketful can be drained away, the water level in the bath will not rise. But if you throw in several buckets quickly one after the other in this same bathtub, the level will rise because the amount of water is too much to drain away.

The amount of water that can be drained away in a period of time is called the drainage capacity. For a polder, for example, the drainage capacity may be 15 millimeters per day. This means that when the rainfall intensity is 15 millimeters a day, it can be drained away without causing a rise in the surface water level.

Try this: click on the bucket to fill the tub! Try filling slowly, then faster.

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