*3.7. Evaluation of Adaptation Strategies*

Considering the negative effect of climate change on crop yield arising from increased temperature and decreased precipitation, this study evaluated the capabilities of adaptation strategies to improve current and future crop yield. Four agricultural management strategies were simulated in the WEAP-MABIA crop model. These strategies included a combination of changing planting date with the application of full irrigation, use of

rainwater harvesting, application of the deficit irrigation method, and the use of efficient irrigation devices. Table 6 presents changes in crop yield with the adoption of changing planting date and full irrigation technique for both baseline and projected climate (RCP 4.5 and RCP 8.5) scenarios for the period 2010–2039, 2040–2069, and 2070–2099 respectively. Results revealed that maize and soya bean yields will increase by 39 to 270% and by 52 to 138% while dry bean and sunflower was expected to increase by 45 to 144% and 15 to 57% respectively.

**Table 6.** Changes in crop yield with the adoption of a change in planting date along with full irrigation technique for the baseline and projected climate scenarios for the periods 1976–2005, 2010–2039, 2040–2069, and 2070–2099.


For the application of rainwater harvest, results from the analysis revealed an increase in the mean potential yield ranging between 14 to 21% and 5 to 8% for maize and soya beans respectively. For dry beans, an increase of between 4 to 10% was expected while an increase of 5 to 13% was expected for sunflower yield, as presented in Table 7. The analysis of the results also revealed that the ability of RWH to improve crop yield in the Olifants catchment was expected to continue toward the mid and end-term for both RCPs.

**Table 7.** Changes in crop yield with the adoption of rainwater harvesting for the baseline and projected climate scenarios for the periods 1976–2005, 2010–2039, 2040–2069, and 2070–2099.


With regards to the application of the deficit irrigation method as an adaptive strategy. The results illustrated in Table 8 show that the yield of maize was expected to decrease by 1 to 3% for both the baseline and projected climate scenarios. While an increase of 2 to 4% was anticipated for the soya beans yield. For dry beans, a different situation was observed as there were no changes in the yield for both baseline and projected climate scenarios with the exception of RCP8.5 which showed an increase of 4 and 5% for the early term (2010–2039) and mid-term (2040–2069) respectively. Similar to dry beans, the yield of sunflower remains unchanged.


**Table 8.** Changes in crop yield with the adoption of the deficit irrigation method for the baseline and projected climate scenarios for the periods 1976–2005, 2010–2039, 2040–2069, and 2070–2099.

> Under the application of the efficient irrigation device, results demonstrated in Table 9 show an increase in maize yield for both baseline and projected climate, while there were no changes in the yield of soya beans, dry beans, and sunflower.

**Table 9.** Changes in crop yield with the adoption of an irrigation efficiency device for the baseline and projected climate scenarios for the periods 1976–2005, 2010–2039, 2040–2069, and 2070–2099.


The evaluation of adaptation measures in this study show that crops respond to adaptive measures differently. It is, however, important to note that not all adaptive strategies can improve crop yields. Among the different adaptation strategies evaluated, the combination of changing the planting date with full irrigation technique and the application of rainwater harvesting were found to be the most suitable measures for all crops studied.
