Quantifying the effects of contour trenching: A field scale case study in Murcia, Spain

Abstract

This research aimed to quantify the effects of contour trenching in terms of soil moisture content and erosion rates on a hillslope scale in the region of Murcia, Spain. Fieldwork was executed to obtain the required data on local soil and infiltration characteristics that serves as input for the process of the contour trench design. Infiltration curves were constructed and statistically analysed as well as fitted to the Horton equation. The contour trench designs that best fitted local conditions were evaluated hydrologically in HYDRUS 2D. Significant increases in soil moisture content were found up to a lateral distance of 1.15 meter from the trenches. The earth mound proved to limit the lateral dispersion downslope of the trench through its capillary pull. Furthermore, the implementation of a contour trench system did not show to impact the cumulative root water uptake of an agricultural hillslope, where the loss of cultivatable surface that is the result of the implementation of the trenches is compensated by the increased soil moisture contents in the inter trench zone. Finally, a revised Morgan-Morgan Finney model was applied to evaluate the impact of contour trenches on annual erosion rates, which was shown to be reduced by 97% through the implementation of trenches.