Contour trenching explained

Contour trenching (a.k.a., Continuous Contour Trench or CCT)^[1] is an agricultural technique that can be easily applied in arid sub-Sahara areas to allow for water, and soil conservation, and to increase agricultural production.^{[2] [3] [4] [5]}

Between two trenches crops can benefit during the growing season (when there is less rain) from the subsoil water reserve gathered during the rainy season.

Advantages

Immediate advantages are the following:

• The rain water does not immediately run off the hill,
• Water does not evaporate uselessly
• The water balance is enhanced
• Crops do not suffer later on from water shortage,
• Fertile soil particles are not lost by water and wind erosion.
• When the sun shines on the water, light and heat are reflected onto plants on the northern shore of the trench, this effect and the increased humidity create micro climates in the area. These micro climates can support plants from different hardiness zones.

Techniques

Trenches can be artificially dug along the contour lines, across the slope so that water flowing down the hill is retained by the trench, and is infiltrating the soil below.

Implementation

Depending on the slope of the hill, the parallel trenches can be closer or further from one another.

Manually dug trenches are smaller. Machine dug trenches can be deeper. The dimensions, and the format of the trench should correspond to the local climate and soil conditions. The trench should be big enough to keep all the water; no water should spoil over the downhill border. The upside of the trench should be protected against erosion, by means of e.g. grass, shrubs, or fabric.

See also

• Swale (landform)
• Keyline design
• Terrace (agriculture)
• Groundwater recharge
• Hydrology (agriculture)
• Infiltration (hydrology)

Notes and References

1. Continuous Contour Trench (CCT): Understandings of hydrological processes after standardisation of dimensions and development of a user-friendly software . 10.1016/j.still.2020.104792 . 2021 . Nagdeve . Mahendra . Paul . Pranesh Kumar . Zhang . Yongqiang . Singh . Rajendra . Soil and Tillage Research . 205 . 2021STilR.20504792N .
2. Web site: Contour Trenching and Terraces . 2016-05-02 . https://web.archive.org/web/20160331141916/http://www.fws.gov/fire/ifcc/esr/Treatments/contour-trenching.htm . 2016-03-31 . dead.
3. Decision support system for contour trenching. Anand . Vishwakarma. Vinod C. Pande. Academia.edu.
4. Web site: Sustainable Watershed Development by Refilled Continuous Contour Trenching Technology. Parag. A. Sadgir . G. K. Patil . V. G. Takalkar. Indiaenvironmentportal.org.in. 26 January 2019.
5. Web site: Experimental Forests, Ranges, and Watersheds in the Northern Rocky Mountains : A Compendium of Outdoor Laboratories in Utah, Idaho, and Montana. Fs.fed.us\accessdate=26 January 2019.