Sediment Influx and Its Drivers in Farmers’ Managed Irrigation Schemes in Ethiopia

Henk Ritzema,Zerihun Anbesa Gurmu,Charlotte de Fraiture,Mekonen Ayana,Michel Riksen

doi:10.3390/w13131747

Abstract

Excessive soil erosion hampers the functioning of many irrigation schemes throughout sub-Saharan Africa, increasing management difficulties and operation and maintenance costs. River water is often considered the main source of sedimentation, while overland sediment inflow is overlooked. From 2016 to 2018, participatory research was conducted to assess sediment influx in two irrigation schemes in Ethiopia. Sediment influx was simulated using the revised universal soil loss equation (RUSLE) and compared to the amount of sediment removed during desilting campaigns. The sediment deposition rate was 308 m3/km and 1087 m3/km, respectively, for the Arata-Chufa and Ketar schemes. Spatial soil losses amounts to up to 18 t/ha/yr for the Arata-Chufa scheme and 41 t/ha/yr for the Ketar scheme. Overland sediment inflow contribution was significantly high in the Ketar scheme accounting for 77% of the deposited sediment, while only 4% of the sedimentation at the Arata-Chufa scheme came from overland flow. Feeder canal length and the absence of canal banks increased the sedimentation rate, however, this was overlooked by the stakeholders. We conclude that overland sediment inflow is an often neglected component of canal sedimentation, and this is a major cause of excessive sedimentation and management problems in numerous irrigation schemes in sub-Saharan Africa.

Highlights

Excessive sediment influx hampers the function of many water resource systems and irrigation infrastructures in sub-Saharan Africa, causing storage capacity reductions, opportunity costs and safety hazards [1,2,3,4,5,6,7]
The impact of excessive sedimentation is especially high in countries such as Ethiopia, where overland soil erosion is severe and limited resources are available to address the problem [8,9,10]
Since study area is characterized by data we modeled soil erosion the revised universal soil lossour equation (RUSLE)

Summary

Introduction

Excessive sediment influx hampers the function of many water resource systems and irrigation infrastructures in sub-Saharan Africa, causing storage capacity reductions, opportunity costs and safety hazards [1,2,3,4,5,6,7]. The impact of excessive sedimentation is especially high in countries such as Ethiopia, where overland soil erosion is severe and limited resources are available to address the problem [8,9,10]. Soil erosion is a major factor limiting agriculture due to the loss of fertile topsoil. It has a prolonged effect on the agricultural sector as the rate of soil loss exceeds the soil formation rate [11]. Many irrigation schemes have been abandoned or operate far below full capacity [12,13]. In Ethiopia, most irrigation systems are the river diversion type

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Discussion

Conclusion