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{{stub}}__NOTOC__[[Image:Tyrolean_weir_icon.pngLanguage-box|right]][[Image:english_link=Water Portal / Rainwater Harvesting / Surface water / Tyrolean weir.JPG|thumbfrench_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 |rightkorean_link= Coming soon |150pxchinese_link=提洛尔堰 |indonesian_link= Bendungan Tyrolean weir]]| 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. Bourman, Aqua for All.]] 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 itself does not clean or purify the water.
{| border="1" cellpadding=Technical specification"5" cellspacing="0" align="center"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="50%" style="background:#efefef;" | Advantages! style="background:#f0f8ff;" | Disadvantages|-30 degree downward slope. Large stones, branches | valign="top" | - More reliable and large leaves cannot pass between the rods, cheaper compared to dams and are prevented from entering the gutter. Because the rods / plate slopes downward, the material water inlet structures in the stream is pushed river embankments <br>- They do not affect water flow to communities downstream, until it drops over the end of the weir.| valign="top" | - None known|}
===Resilience to changes in the environment=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.
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.
==Manuals== Maintenance==Movies== ==External links== ==References==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.
===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.