Changes

River-bottom or Tyrolean intakes for drinking-water systems are usually used in small rivers and streams where the sediment content and bed load transport are low. The water is abstracted through a screen over a canal (usually made of concrete and built into the river bed). The bars of the screen are laid in the direction of the current and sloping downwards, so that coarse material can- not enter. From the canal, water enters a sand trap and then may pass a valve and flow by gravity, or be pumped into the rest of the system.

==Construction, operations and maintenance==

For small community water supplies only small quantities of water are needed and often very simple intake structures can be used. With a per capita water use of 30 litres/day and the peak intake 4 times the average water demand, 1000 people would require an intake capacity of only 1.4 l/s. A 150 mm diameter intake pipe would be sufficient to keep the entrance velocity 0.1 m/s. If an entrance velocity of 0.5 m/s were allowed, a pipe as small as 60 mm would be adequate.