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

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{{Language-box|english_link=Water Portal / Rainwater Harvesting / Surface water / River-bottom intake | french_link= Prise d'eau en lit de rivière | spanish_link= Toma de Fondo | hindi_link=वाटर पोर्टल / वर्षाजल संचयन / सतही जल / नदी-तल से जल-संग्रहण | malayalam_link= Coming soon | tamil_link= Coming soon | korean_link= 워터 포탈/빗물 수집/지표수/강 바닥 흡입구 | chinese_link=河底引水口 | indonesian_link= Asupan Dasar Sungai | japanese_link= 川底取水口 }} [[Image:intake icon.png|right|80px]]__NOTOC__'''River-bottom or Tyrolean intakes ''' (different than a [[Tyrolean weir]]) 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 cannot 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.

Intake designs aim to avoid clogging and scouring and to ensure the stability of the structure even under flood conditions. Where the river transports no boulders or rolling stones, an unprotected intake may be adequate.

===Suitable conditions===

* Rivers with little sediment and bed load.

* Where there is adequate flow.

* Upstream of bridges (to reduce velocity/turbulence).

===Resilience to changes in the environment===

====Drought effects on concrete====

More information on managing drought: [[Resilient WASH systems in drought-prone areas]].

===Construction, operations and maintenance===

[[Image:River-bottomIntake.JPG|thumb|right|300px|River-bottom intake mechanics. <br> Click image to zoom.]]

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.

* During the dry season, there may not be enough water in the river or stream to supply all users.

==Costs=Manuals, videos and links===* [http://www.lifewater.org/resources/rws1/rws1p4.pdf Choosing Where to Place Intakes.] Water for the World.

==Field experiences== ==Manuals, videos, and links==* [http://www.lifewaterircwash.org/resourcessites/rws1default/rws1p4files/Smet-2002-Small_TP40.pdf Choosing Where to Place IntakesSurface water intake and small dams].] Water for the WorldChapter 11. Revised by Nhamo Masanganise.

===Acknowledgements===

* Masanganise, Nhamo. [http://www.samsamwater.com/library/TP40_11_Surface_water.pdf Surface water intake and small dams].

* Brikke, François, and Bredero, Maarten. [http://www.washdoc.info/docsearch/title/117705 Linking technology choice with operation and maintenance in the context of community water supply and sanitation: A reference document for planners and project staff] or ([http://www.who.int/water_sanitation_health/hygiene/om/wsh9241562153/en/ alternative link]). World Health Organization and IRC Water and Sanitation Centre. Geneva, Switzerland 2003.

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