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Water Portal / Rainwater Harvesting / Surface water / Road runoff harvesting

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[[Image:road runoff map.jpg|thumb|right|225px|This map illustrates how you locate the channels coming from the road. Click image to zoom in. Drawing: UNDP]]

This technology is categorized under WOCAT (World Overview of Conservation Approaches and Technologies) as a combined structural/ vegetative measure. [[Bunds]] and channels are stabilized with perennial grass. Its purpose is primarily to increase soil moisture for crop production, and it achieves impact through water harvesting. In soil conservation terms it reduces land degradation and soil erosion by water.

Runoff is led to the farm from the tar road in a main excavated channel of about 300 metres length, which cuts through a neighbour’s farm. There are also supplementary channels which lead runoff from a hillside. The estimated catchment area is (at least) 10 hectares in size. This supplies water to a cultivated area of about 5 ha. The main channel leads runoff into the farm through an initial fanya chini structure (a channel with the earth thrown downslope). When the runoff reaches the end of the channel, it is diverted round into a similar structure, which leads the water in the opposite direction. To make a simplification, runoff water is conveyed in a zigzag fashion, or ‘reticulated', through the farm. At certain points the farmer has put water control gates in specific channels, to select the direction of the flow.

Winona

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