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UNESCO-IHE (2009)

Performance assessment of water distribution in large scale irrigation : Case study of Chokwe Irrigation System in Mozambique

Julaia, C. de S

Titre : Performance assessment of water distribution in large scale irrigation : Case study of Chokwe Irrigation System in Mozambique

Auteur : Julaia, C. de S

Etablissement de soutenance : UNESCO-IHE Institute for Water Education Netherlands

Grade : Master of Science (MS) 2009

Résumé partiel
In the agriculture-based countries, which include most of Sub-Saharan Africa, agriculture and its associated industries are essential to growth and to reducing mass poverty and food insecurity. Mozambique, where this research was carried out, is one of the agriculturebased countries and this activity provides food security and is an important source of income for 75% of the 20 million inhabitants in the country. Agriculture is by far the largest user of water, contributing to water scarcity. Concerns about scarcity of water have focused attention on irrigation, the largest water-using sector worldwide. Improvement of the efficiency and distribution uniformity of irrigated agriculture can minimize the gap between potential crop water requirements and actual water use. The study area of the present research is Chokwe Irrigation System, which consists of an earth canal having a length of 14 km and current capacity of 45 m3/s (canal geral). This canal is subdivided into two canals one main and one secondary, the left earth canal (secondary canal) partially lined and the right earth canal (main canal) with a nominal discharge of 0.8 m3/s and 29 m3/s respectively. The right earth canal is then subdivided into two main canals, the “canal do rio” with a nominal discharge of 10 m3/s and the Nwachicoluane canal with a nominal discharge of 4.5 m3/s. The water is diverted from the main canals to secondary canals or distributors and most of these are earth canals. The drainage system includes tertiary or field drains with depths between 0.7 – 1.0 m which are parallel to tertiary canals. These join the secondary drains which are parallel to secondary canals or distributors, and then finally connected to the main drains. Chokwe Irrigation System is entirely by gravity (except in the upstream part of the system) and the flow control method is upstream control. The major structures in the system consist of AMIL gates, duckbill weirs, sliding gates as water level regulators and baffle distributors and/or sliding gates as discharge regulators. This research was carried out on performance assessment of water distribution in Chokwe Irrigation System in order to check the state of health of the system and also the level of water use. The main objective of the study was to analyse the efficiency of the current water distribution, operation rules on the system, simulate the water flow with a hydraulic model (DUFLOW) and recommend possible solutions for improvement on the water use efficiency.

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