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<p>Water scarcity and increasing agricultural demand necessitate efficient irrigation systems; however, many schemes in Ethiopia operate below their design capacity. This study assessed the hydraulic performance of the Shawe Gindiba Gojo irrigation scheme in Bale Zone of Oromia, with particular emphasis on the influence of Manning’s roughness coefficient on water conveyance and distribution efficiency. Field measurements were conducted at the head, middle and tail sections of main and secondary canals within a 250&#xa0;ha command area using a 3-inch Parshall flume and a current meter. The results revealed clear deviation from the design conditions, with conveyance losses ranging from 2.55 to 34.9&#xa0;L/s and main canal efficiency of 86.1%.In contrast, secondary canals exhibited higher resistance, as indicated by increase in Manning’s roughness coefficient to 0.060 compared with the design value of 0.025. The average DPR was 42.96%, accompanied by a 16.8% delivery deficit and high variability (CV &gt; 28%). Peak demand deficits reached 42%, disproportionality affecting tail-end users. A strong negative correlation (<i>ρ</i> = −0.83, <i>p</i> &lt; 0.01) between roughness and flow velocity indicates that canal deterioration is a primary constraint on system performance. Accordingly, regular maintenance and system recalibration are essential to improve hydraulic performance and ensure equitable water distribution.</p>

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Effects of Manning’s roughness coefficient on the hydraulic performance of irrigated farms: a case study of the Shawe Gindiba Gojo irrigation scheme, Ethiopia

  • 期刊论文

  • 发表日期：

    2026年7月23日

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  • Tilahun Derib Asfaw,
  • Hussen Seyyid

摘要

Water scarcity and increasing agricultural demand necessitate efficient irrigation systems; however, many schemes in Ethiopia operate below their design capacity. This study assessed the hydraulic performance of the Shawe Gindiba Gojo irrigation scheme in Bale Zone of Oromia, with particular emphasis on the influence of Manning’s roughness coefficient on water conveyance and distribution efficiency. Field measurements were conducted at the head, middle and tail sections of main and secondary canals within a 250 ha command area using a 3-inch Parshall flume and a current meter. The results revealed clear deviation from the design conditions, with conveyance losses ranging from 2.55 to 34.9 L/s and main canal efficiency of 86.1%.In contrast, secondary canals exhibited higher resistance, as indicated by increase in Manning’s roughness coefficient to 0.060 compared with the design value of 0.025. The average DPR was 42.96%, accompanied by a 16.8% delivery deficit and high variability (CV > 28%). Peak demand deficits reached 42%, disproportionality affecting tail-end users. A strong negative correlation (ρ = −0.83, p < 0.01) between roughness and flow velocity indicates that canal deterioration is a primary constraint on system performance. Accordingly, regular maintenance and system recalibration are essential to improve hydraulic performance and ensure equitable water distribution.