Spatial and Temporal impacts of stone bunds on soil physical properties: a case study in the Northern Ethiopian Highlands
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Christoph Schuerz. (30/1/2014). Spatial and Temporal impacts of stone bunds on soil physical properties: a case study in the Northern Ethiopian Highlands. Vienna, Austria: University of Natural Resources and Life Sciences, Center for Development Research (BOKU - CDR).
Abstract
Central issue of rain fed agriculture systems in the Ethiopian highlands is to store rain
water in the soil during the rainy season. The aim is to maximize plant available water and
to reduce surface runoff and soil erosion. Stone bunds are a common practice for soil and
water conservation, influencing the translation processes of surface runoff. However,
changes in surface hydrology affect the temporal and spatial properties of soil physical
parameters.
The objective of this work is to find a relationship between the spatial distribution of soil
properties and the location of the stone bunds, but also to monitor the temporal behavior
of those soil parameters, to better understand the impact of stone bunds on soil water
movement. The research area is located in the Gumara-Maksegnit watershed in Northern
Ethiopia. There, two representative transects were selected: One transect crosses three
fields with soil and water conservation measures applied perpendicular to them on a
length of approximately 71 m. The second transect crosses the same hill slope in an area
without conservation structures at a length of 55 m. During the rainy season in 2012 soil
physical properties were monitored in specific spatial and temporal intervals. The
measurements included bulk density, soil texture, and volumetric water content. Tension
infiltration experiments were performed to determine saturated hydraulic conductivity for
areas near stone bunds and the center of the fields on one hand, but also to derive soil
water characteristics for the certain positions at the hill slope. Slope steepness and stone
cover along the transects were assessed, using survey and photogrammetric analysis.
The analyses that were used in this approach were able to reveal spatial and temporal
characteristics of the assessed soil properties under the influence of stone bunds. For
near surface volumetric water content a clear periodic behavior along the stone bunds
was found, with significantly higher values in the vicinity of the stone bunds. Additionally,
an early increase in water content over the rainy season was found for the transect with
SWC. The bulk density showed significantly lower values in the zones where
accumulation of sediment material takes place. Saturated hydraulic conductivity but also
soil water characteristics show temporal changes but also spatial differences that are
most likely induced by differences in soil structure. The strongest spatial relationship was
found for inclination and near surface soil water content.