NWP102A: Design a basic water system model

How water flows

How water flows

Reflect:

Why does water flow in a particular direction? What things affect how fast the water moves?

Imagine a river with a waterfall:

  • The riverbed is wide and sandy, and water flows downhill from north to south until it comes to a steep rocky drop.
  • The water flows over the drop and crashes down to the river bed below (this is the part we call a waterfall).
  • The river bed at the bottom is made of smooth rock and is narrow with steep sides. The water in this part of the river flows much faster than it does at the top of the waterfall.

Think about it:

Water poured from a bucket will naturally flow towards the ground. Water always flows downhill because of gravity.

Water coming out of a water pistol will be travelling fast. It is pushed out using force. The speed water travels at depends on the amount of force working on it.

When water is poured into a funnel, the wide part (cup) of the funnel will fill up quickly. That is because water can move faster in the wide area but slows down when it hits the narrow neck. It pushes harder on the sides of the funnel as it moves through the narrow bottom. As water moves from a wider space to a narrower space the water pressure gets higher.

Rain travelling over the surface of a window will move more quickly than rain running down the wall. This is because travelling over a rough surface slows it up. Water travels more slowly over rough surfaces than it does over smooth ones because there is more friction.

Gravity and force affect the direction water flows in. Gravity, force and friction affect water pressure and how fast the water flows.

Text alternative

1. The riverbed is wide and sandy, and water flows down from north to south. The water is flowing downhill because of gravity.

The width of the container (the riverbed) is wide. This lowers the water pressure. The river bed is rough. This friction causes the water to flow more slowly.

2. The waterfall flows over the drop and crashes down to the river bed below. The water is flowing down the steep drop because of gravity.

3. The river bed at the bottom is made of rock and is narrow with steep sides. The width of the container (the riverbed) is narrow. This increases the water pressure.

Please download the Adobe Flash Player from www.adobe.com to view this interaction, or use the text alternative instead.

Measuring water flow

Water meter

So how can water be measured?

Water meters measure the amount of water that flows over a given area in a certain amount of time. The standard unit of measurement is L/hr (how many litres of water flow over the meter in an hour).

Water meters are used to measure water flow in:

Meters are attached between all scheme water distribution systems and consumer supply lines. They provide information about how much water is being used in the business or household and this determines how much the consumer pays for their water.

Meter readings are also used to provide statistics about how much water is being used across the whole system. This is important as it allows water service providers to monitor how much water is available in water storage and catchment systems and to put water restrictions in place in times of low supply.