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Water Portal / Rainwater Harvesting / Surface water / Tyrolean weir

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[[Image:Tyrolean_weir_icon.png|right]]
Dams and water inlet structures in embankments are vulnerable and expensive elements in river-fed water systems. They are easily damaged by floods, underflow, seepage and suffer from build-up of sediment or rubbish in the water. The Tyrolean weir forms a more reliable and cheaper alternative. Water is abstracted through a screen (or inlet) over a gutter, usually made of concrete and built into the riverbed. The screen on the crest should slope downstream (15-30 degrees), to increase flow velocities and prevent sediment carried by the stream from blocking it. From the gutter, water enters a pipeline, which drains into a sedimentation tank and then flows by gravity into the rest of the system.
[[Image:Tyrolean weir.JPG|thumb|right|150px|Tyrolean weir]]
 
A Tyrolean weir is a water inlet structure in which water is abstracted from the main flow through a screen over a gutter. The gutter is usually made of concrete and built into the river bed. The screen on the crest should slope downstream (15-30 degrees), to increase flow velocities and prevent sediment carried by the stream from blocking it. From the gutter, water enters a pipeline, which drains into a sedimentation tank and then flows by gravity into the rest of the system.
 
Dams and water inlet structures in embankments are vulnerable and expensive elements in river-fed water systems. They are easily damaged by floods, underflow, seepage and suffer from build-up of sediment or rubbish in the water. The Tyrolean weir forms a more reliable and cheaper alternative.
 
==History and social context==
 
==Suitable conditions ==
Tyrolean intakes are used in small permanent rivers and streams where the sediment content and bed load transport are low, or on the crest of a dam spill.
 
The weir or intake should be carefully sited.
 
The weir itself does not clean or purify the water.
{{procontable | pro=
- More reliable and cheaper compared to dams and water inlet structures in river embankments <br>
| con=
}}
}}==Technical specification== ====Operation==== ====Maintenance====Several visits per year to the site are necessary for inspection, cleaning and minor repairs. Overall, maintenance is easy to carry out due to low-tech structure and the use of local labour and materials. Regular inspection and cleaning of the grit / rack and possibly the gutter and sedimentation tank is required during and after storm periods. ====Manufacturing ====The threshold can be a concrete elevation above the rocky bed of a mountain stream, or a vertical low weir structure, anchored in the embankment.  The capacity of the inlet pipe / drain (diameter and gradient) should be 30% more than the design flow and have an uniform gradient to prevent accumulation of sand. The sedimentation tank can accumulate 1.5-2 m<sup>3</sup> of deposits and allows water to filter for 10 to 30 minutes at very low speed. It is cleaned by washing it out.
== Costs ==
==Cost==
* Material (excluding the pipe and sedimentation tank): US$ 300 - 600.
* Labour (if site is easily accessible): 30 - 50 man days.
* Operation and maintenance: several visits per year for inspection, cleaning and minor repairs. Overall easy to carry out due to low-tech structure and the use of local labour and materials.
==Country experiences==
== Applying conditions Manuals==
* Tyrolean intakes are used in small permanent rivers and streams where the sediment content and bed load transport are low, or on the crest of a dam spill. * The threshold can be a concrete elevation above the rocky bed of a mountain stream, or a vertical low weir structure, anchored in the embankment. * The capacity of the inlet pipe / drain (diameter and gradient) should be 30% more than the design flow and have an uniform gradient to prevent accumulation of sand.* The sedimentation tank can accumulate 1.5-2 m3 of deposits and allows water to filter for 10 to 30 minutes at very low speed. It is cleaned by washing it out.==Movies==
==External links==
== Maintenaince References==
* Regular inspection and cleaning of the grit / rack and possibly the gutter and sedimentation tank is required during and after storm periods.
== Considerations ==
* The weir or intake should be carefully sited.
* The weir itself does not clean or purify the water.
{{Joinus}}
 
== External links ==
* General Background [http://www.aquaforall.nl www.aquaforall.nl]
Marktielewestra
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