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Kwame Nkrumah University of Science and Technology (2013)

Assessing the impacts of climate change on the availability of stored water for irrigation purposes in the semi-arid areas of Ghana : A Case Study of Tono and Vea Irrigation Projects

Kusi, Kwabena Antwi

Titre : Assessing the impacts of climate change on the availability of stored water for irrigation purposes in the semi-arid areas of Ghana : A Case Study of Tono and Vea Irrigation Projects.

Auteur : Kusi, Kwabena Antwi

Université de soutenance : Kwame Nkrumah University of Science and Technology

Grade : Master of Science (2013)

Résumé
This study investigates the potential impacts of climate change on the availability of stored water for irrigation in the semi-arid region of Ghana. The study was based on two medium-sized reservoirs – Tono and Vea – used for irrigation purposes and managed by the Irrigation Company of Upper East Regions, ICOUR. Historical water abstraction from the Tono and Vea reservoirs were estimated. The irrigation needs of four major crops (rice, tomato, pepper and onion) grown during the dry season were computed using the CROPWAT/CLIMWAT model. Future climatic conditions for the years 2020, 2040, 2060 and 2080 were determined based on synthetic and empirical downscaling of AR4-CNCM3 GCM scenarios. The historical water abstraction via evaporation losses was computed for both reservoirs and subsequently their future evaporation losses was also estimated by the use of Thornthwaite‟s evapotranspiration formula. Finally, future irrigation needs were computed based on future climatic conditions with plausible climate change adaptation strategies suggested. Results of the study suggest that the net irrigation water requirements of the four crops will increase by about 1.4% – 9.8% due to an increase in mean temperature between 1°C - 3°C with a corresponding increase in rainfall of about 10%-35.5% depending on the type of climate change scenario and time slices. Climate change will relatively not have much significant impact on Tono irrigation project because future estimated total water abstraction (ETWA) when the total irrigable area at Tono is cultivated with rice will be about 71% to 77% of the maximum storage capacity between 2020 and 2080. Therefore the total irrigable area of 2490 ha could be utilized for the cultivation of rice and usage by other sectors since there is abundance of water. Climate change will however, have a major toll on Vea reservoir as the ETWA when the historical maximum land areas are cultivated exceeds the total water use allocated for irrigation and evaporation losses (TWAIE) ; and also the dam will be in a state of distress when all the irrigable lands are used solely for rice cultivation as an additional 3.95Mm3-6 Mm3 of water will be required to augment production denying other sectors usage.

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