Improving spate flow diversions in spate irrigation intake structures

ABSTRACT

This study evaluated alternatives to the main intake designs of spate irrigation structures. Relevant data were collected from a field and offices. Four scenarios were developed based on current problems. The Delft3D model was employed to simulate hydrodynamic and morphodynamic flow characteristics around the main intake. The study showed that increasing the deflection angle from 120° to 150° for a 3-m-wide intake can improve the irrigation water abstraction by 21%. Changing the width from 3 to 5 m at 120° can improve the irrigation water abstraction by 81%. In addition to changing the width, increasing the deflection angle to 150° can improve the spate irrigation water abstraction by 101%. These interventions did not reduce the sediment deposition at the intake. However, the enhanced supply of water through main spate flow gates may convince farmers not to block scour sluice gates. Based on the pure design, an intake width of 5 m and a deflection angle of 150° can be recommended.

KEYWORDS:

• Spate irrigation
• spate diversion structure
• water intake
• sedimentation
• floodwater abstraction

Acknowledgments

The authors would like to thank to the Netherlands Fellowship Program (NFP) and Tigray Agricultural Research Institute (TARI) for the financial support. Special thanks to Professor Charlotte de Fraiture for her close supervision during the research implementation period. The authors also acknowledge to Mr. Kibrom Ambachew Gebrehiwet for his valuable support during model setup and calibration. Last but not least, we would like to thank all staff of Alamata agricultural research center for their valuable support during the field data collection.

Disclosure statement

No potential conflict of interest was reported by the authors.