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Water Portal / Rainwater Harvesting / Surface water / River-bottom intake

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→‎Construction, operations and maintenance

==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.

The bottom of the intake structure should be at least 1m above the riverbed to prevent any boulders or rolling stones from entering. The intake structure must always include one or more baffles or screens to keep out debris and floating matter such as tree trunks and branches. It is advisable to use “passive” screening that does not create turbulent flow conditions. To reduce the drawing in of silt and suspended matter, the velocity of flow through the intake should be low, preferably less than 0.1 m/s. To make use of the natural current to help cleaning of screens, the following tips are suggested:

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