Dams and water inlet structures in embankments are vulnerable and expensive elements in river{{Language-fed box|english_link=Water Portal / Rainwater Harvesting / Surface water systems/ Tyrolean weir | french_link= Coming soon | spanish_link= Toma Tirolesa | hindi_link= वाटर पोर्टल / वर्षाजल संचयन / सतही जल / टाइरोलीन मेड़ | malayalam_link= Coming soon | tamil_link= Coming soon | korean_link= Coming soon | chinese_link=提洛尔堰 | indonesian_link= Bendungan Tyrolean | japanese_link= 水のポータルサイト／雨水貯留／表面水／チロリアン式堰 }} [[Image:Tyrolean_weir_icon.png|right|80px]][[Image:Tyrolean weir.JPG|thumb|right|200px|Tyrolean weir|Man checking the grid at a Tyrolean Weir. Tanzania. Photo: D. They are easily damaged by floodsBourman, underflow, seepage and suffer from build-up of sediment or rubbish in the waterAqua for All. The ]] A '''Tyrolean weir forms ''' is a more reliable and cheaper alternative. Water water inlet structure in which water is abstracted from the main flow through a screen (or inlet) over a gutter, . The gutter is usually made of concrete and built into the riverbedriver 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. ===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.
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! width="50%" style="background:#efefef;" | Advantages
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| valign="top" | - More reliable and cheaper compared to dams and water inlet structures in river embankments <br>- They do not affect water flow to communities downstream| valign="top" | <br><br>- None known
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===Resilience to changes in the environment===
====Drought effects on cement====
'''Effects of drought:''' Badly made concrete or cracked linings (e.g. in tanks, dams, waterways, wells, and other structures). <br>
'''Underlying causes of effects:''' Less water used for curing; Impure water used for mixing. <br>
'''To increase resiliency of WASH system:''' Ensure adequate mixing, ratios, purity of ingredients; Minimize water content in mixture; Ensure adequate curing.
== Costs ==
* Material (excluding the pipe and sedimentation tank)More information on managing drought: US$ 300 [[Resilient WASH systems in drought- 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 materialsprone areas]].
===Construction, operations and maintenance===
[[Image:Tyro weir.jpg|thumb|right|200px|Tyrolian weirs are meant to intake water from mountain rivers that are very turbulent. Photo: [http://www.tuwien.ac.at/en/tuwien_home/ Vienna University of Technology]]]
== Applying conditions ==A Tyrolean weir can either consist of parallel rods or a perforated plate, installed in the flow direction over the width of the stream with a 15-30 degree downward slope. Large stones, branches and large leaves cannot pass between the rods, and are prevented from entering the gutter. Because the rods / plate slopes downward, the material in the stream is pushed downstream, until it drops over the end of the weir.
* 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 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.
====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.
== Considerations == * The weir or intake should be carefully sited. * The weir itself does not clean or purify the water.* Regular inspection and cleaning of the grit / rack and possibly the gutter and sedimentation tank is required during and after storm periods.
===Costs===
* Material (excluding the pipe and sedimentation tank): US$ 300 - 600.
* Labour (if site is easily accessible): 30 - 50 man days.
===Manuals, videos and links===
* [http://www.samsamwater.com/library/TP40_11_Surface_water.pdf Surface water intake and small dams]. Chapter 11. Revised by Nhamo Masanganise.
== External links =Acknowledgements===* General Background CARE Nederland, Desk Study: [http://www[Resilient WASH systems in drought-prone areas]].aquaforallOctober 2010.nl www.aquaforall.nl]