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Water Portal / Rainwater Harvesting / Groundwater recharge / Contour trenches

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[[Image:contour trch icon.png|right]]

[[Image:contour_trench.JPG|thumb|right|~~300px~~200px| Contour trench under construction and measuring contours with hose pipes. Photo: WTC.]]

At its simplest, contour trench construction is an extension of the practice of plowing fields at a right angle to the slope. Contour trenches are ditches dug along a hillside in such a way that they follow a contour and run perpendicular to the flow of water. The soil excavated from the ditch is used to form a berm (a narrow shelf) on the downhill edge of the ditch. The berm can be planted with permanent vegetation (native grasses, legumes) to stabilize the soil and for the roots and foliage in order to trap any sediment that would overflow from the trench in heavy rainfall events.

==Construction, operations and maintenance==

[[Image:Contour_Trench.JPG|thumb|right|~~300px~~200px|An example of contour trench in Kitenden, Vietnam. <br> Source: Westerveld Conservation Trust]]

In order to efficiently capture runoff in a catchment through appropriately sized trenches, the following information and analysis is needed:

* Catchment area, gathered from topographical maps

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