Epsilon Archive for Student Projects

Abstract

In this study, I examined how land use change affects the partitioning of water and how soil-plant interactions are impacted by yearly rainfall at a stand scale. Even though many studies have been conducted to evaluate the extent of land use change and the economic impacts, few have attempted to study the rapid farmer-driven afforestation with Acacia decurrens and also disaggregated dry, normal and dry seasons at stand scale. Most of the studies are done on a large scale or capture catchment.
The purpose of this study was to analyse how changes in land use from annual to perennial crops affected water balance at a stand scale in the Ethiopian highlands. A recent change in land use in Fagita Lekoma, Ethiopia, has seen farmers adopt planting A. decurrens rather than teff.
To study the impact of changing land use from annual to perennial cropping on the water balance, a crop water productivity model called AquaCrop model 6.1 was used. This study used a long-term climate dataset (1982-2020) to represent, dry, normal and wet Kiremt seasons. In this study, the land use change for A. decurrens stands aged 1 to 4 years were compared to annual teff cultivation.
The key findings from this study are that afforestation with A. decurrens increases actual evapotranspiration (ETa) and reduces runoff. The estimated annual mean ETa for afforestation with A.decurrens from this study was 497 mm/y, 474 mm/y, and 461 mm/y during the dry, normal, andwet Kiremt seasons, respectively. In contrast, the annual mean ETa during teff cultivation rangedfrom 322 mm/y during the dry Kiremt season to 346 mm/y during the normal Kiremt season and297 mm/y during the wet Kiremt season. Further, the annual mean runoff for teff cultivation duringthe dry, normal, and wet Kiremt seasons was 74 mm/y, 330 mm/y, and 636 mm/y, respectively. Onthe other hand, surface runoff during afforestation with A. decurrens was 13 mm/y, 56 mm/y, and144 mm/y during the dry, normal, and wet Kiremt seasons respectively. Lastly, during this study,results show an unexpected high annual mean drain during afforestation with A. decurrens. Thedrain was 408 mm/y, 1,574 mm/y and 1,171 mm/y during the dry, normal and wet Kiremt seasonsrespectively. While Teff cultivation had an annual mean drain of 413 mm/y during the dry season,956 mm/y during the normal Kiremt season, and 1,208 mm/y during the wet Kiremt season.
The results of this study suggest that afforestation with A. decurrens in Ethiopian highlands will likely result in a downstream effect of reducing stream flow during dry periods due to increased ETa. However, more information on crop parameters in the model could alter this conclusion.