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Contour trenching for water retention

Contour trenching for water retention is the excavating of trenches along contours to slow runoff, improve infiltration, and protect crops. Contour trenching is a water retention and soil conservation method. Trenches are dug along the contour lines of a slope. When water flows downhill, it is now intercepted by the trenches, which slows the speed of water flow. As water flow is slowed down, the trenches create time for the water to infiltrate into the soil of the slope. This is an effective method to restore soil health in deforested areas and can also be very useful for farmers having plots on or nearby slopes. 

Feasibility & Local Applicability

Most outdoor cropping systems can implement this. Feasibility depends on plot size, machinery used and slope angle. Hillside ditches allowed reducing surface runoff and soil erosion in slopes of 50 to 71 %. Depending on the slope and the amount of rainfall the slope angle and contours must be adjusted. In a high rainfall area staggered contours can be applied – they control water runoff less than ditches, but this is a necessity for if all water is a blocked a landslide occurs. Contouring and terracing is delicate engineering and requires knowledge and skills. Calculate contours (including distance, angle, point rows, and consequently expected soil erosion) with a method from an authoritative source such as UN, FAO or USDA: 

Co-benefits

Trenches form microhabitats. Water infiltrating in the trenches adds to aquifer recharge.

Equity & Vulnerability Considerations

Involve local cooperatives to build and manage the systems. Knowledge and skill must be present. Education is necessary. 

Costs

Low

Case studies & Examples

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Literature

Adaptation Options Overzicht