Assessment of Potential Environmental Impacts of Two Large Scale Irrigation Schemes in Ethiopia

Abstract

This article presents the findings of a study undertaken to assess environmental
impacts of two selected large scale irrigation schemes on natural resources in
Ethiopia. The study puts special emphasis on linkages and implications of the utilized
water source, ground water hydrology and soil characteristics, on the sustainability of
the selected schemes. In addition, potential interference of irrigation projects with
woodland ecosystems is highlighted. For this purpose primary soil and water data and
data from research reports f rom WonjilShoa Sugar Plantation and Finchaa Valley _
Sugar Estate were collected and analysed using a "before-after" and "with or
without" type of analysis. Rising of groundwater table, water logged within the root
zone of the cultivated sugar cane and elevated EC values within 1m of soil depth
indicate the · risk of secondary salinization at WonjilShoa Sugar Plantation.
Unfavourable EC, SAR and RNa values of the utilized irrigation source in combination
with the CEC of soil and ongoing soil erosion processes suggests that irrigation might
lead to long-term infiltration problems and destruction of the soil structure at Fincha
Sugar Estate. The establishment of the scheme and migration tendencies increased the
pressure on the eco-system of the valleys and led to clearing of wood and grass lands.
To guarantee long-term sustainability, proper study and continuous research of
already implemented and planned large spale irrigation projects is necessary, so that
the positive roles of irrigation could be enhanced and timely mitigation measures
taken for the negative impacts.