Volta

The GCM outputs indicate that no major changes are expected in rainfall for the Volta Basin and climate change mainly will have an impact on temperature and CO2 concentrations. The SWAP runs show that as a result of the latter, rice yields are expected to increase by about 45% and 30% for A2 and B2 scenarios, respectively (Fig. 3.7). Since rice is grown in the wet period, the result of growing rice only under rain-fed conditions was explored. Obviously, yields will be lower compared to irrigated conditions, but if we look at current and future rain-fed yields, no major changes in the mean are expected. However, variation in yields will be higher, and water productivity lower.

The adaptation strategy mentioned here as intensification (adaptation strategy 2) - which includes options such as improved crop variety, denser planting and shorter season - will increase crop yields. Water consumption will be lower and water productivity will be higher under this option. These positive effects are stronger under the A2 scenario than under the B2 scenario.

During the wet season maize is commonly produced under rain-fed conditions and therefore this practice is used as the baseline. A small increase in yields is predicted for the near future, but yields in the distant future are expected to reduce substantially by about 50% (Fig. 3.7). Introducing irrigation will increase yields and will reverse the lower yields expected for 2070-2099 to an increase. As with rice, crop intensification has been explored, but still without irrigation. Such intensification can increase mean yields, but since irrigation was not included, variation in yields will be much more profound.

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