Assessing the impacts of different land uses and soil and water conservation interventions on runoff and sediment yield at different scales in the central highlands of Ethiopia

Abstract

To tackle the problem of soil erosion and moisture stress, the government of Ethiopia introduced a yearly mass campaign where communities get together and implement various soil and water conservation (SWC) and water harvesting (WH) practices. Although the interventions are believed to have reduced soil erosion/sediment yield and enhanced surface and ground water, quantitative information on the impacts of various options at different scales is scarce. The objective of this study was to assess the impacts different land uses, SWC and WH interventions on water and suspended sediment yield (SSY) at plot and watershed scales in the central highlands of Ethiopia. Standard erosion plot experiments and hydrological stations were used to monitor the daily water and SSY during 2014 to 2017. The results show differences between treatments both at plot and watershed scales. Runoff and soil loss were reduced by an average 27 and 37%, respectively due to SWC practices at the plot level. Overall, SWC practices implemented at the watershed level reduced sediment yield by about 74% (in the year 2014), although the magnitude of sediment reduction due to the SWC interventions reduced over time. At both scales it was observed that as the number of years since SWC measures have been in place increased, their effectiveness declined due to the lack of maintenance. This study also revealed that extrapolating of plot data to watershed scale causes over or under estimation of net erosion.

Runoff and soil loss responses of cultivated land managed with graded soil bunds of different ages in the Upper Blue Nile basin, Ethiopia

“…In Ethiopia, rainfall-runoff led soil erosion is indeed a fundamental problem (Adgo et al 2013;Tamene and Vlek 2008) and the worst in the world (Hurni et al 2015b). It is considered to be the main driver of land degradation in the rain-feed agricultural areas of the country (Hurni et al 2015b), significantly affecting both on-site and off-site ecosystems (Yaekob et al 2020). The loss of top fertile soil by water erosion creates severe limitations to sustainable agricultural land use, which lead to reduced soil productivity and food insecurity (Hurni et al 2015a;Taddese 2001;Tamene and Vlek 2008).…”

“…Soil erosion not only is jeopardizing agricultural sustainability (Hurni et al 2015a;Tamene and Vlek 2008;Yaekob et al 2020;Yibeltal et al 2019) but also causes streams, lakes, dams, and reservoirs siltation (Haregeweyn et al 2017;Tamene and Vlek 2008;Yaekob et al 2020), and downstream ecosystem impacts (Haregeweyn et al 2016). This can have severe impacts on irrigation agriculture and related investments in different parts of the country.…”

“…SWC practices by community mass mobilization as a nationwide 30 days public campaign work was strongly implemented since 2009 (Haregeweyn et al 2012). At present, large-scale tree planting has been undertaken and millions of hectares of land have been treated with different conservation measures such as terraces, trenches, and percolation ponds through government-led community mass mobilization (Yaekob et al 2020). The initiatives were targeting to reduce soil erosion (both runoff and soil loss), improving soil fertility, rehabilitation of the degraded land, and increase agricultural productivity (Mekuria et al 2007).…”

Effects of Soil and Water Conservation Structures on Crop Yield, Lemo District, Southern Ethiopia

“…Organic matter loss not only results in reduced water holding capacity and soil degradation but also the loss of plant nutrients which are used to increase yield. This was confirmed by [34] and [6], the major problem to the farm associated with soil erosion come from loss of nutrients and reduced water holding capacity, accounting 50 to 70% of productivity loss. [35] also showed that the effects of erosion from slight to severe on organic matter soil phosphorus level, and plant available water reduces their content from 3% to 1.9%, 31 kg/acre to 20 kg/acre and 7.4% to 3.6%, respectively which in-turn affects productivity of the land.…”

Comparison of soil organic carbon and total nitrogen stocks between farmland treated with three and six years level soil bund and adjacent farmland without conservation measure: In the case of southwestern Ethiopia

“…Similarly, conserved farmland exhibited lower bulk density as compared to un-conserved adjacent farmland at Adaa Berga district, western Ethiopia [ 17 ]. Moreover, soil and water conservation has also a potential to reduce the loss of runoff and soil by improving water retention capacity on treated farm [ 18 ]. The slope gradient treated with soil and water conservation measures for 20 years in Minizr Catchment, Northwest Ethiopia has found a 2.7% slope reduction because of trapped sediment [ 19 ].…”