An account of the Nile would be incomplete without engaging with climate change. Undoubtedly, climate change is going to affect all riparians in the Nile basin by increasing the variability and regional scarcity of water (Goulden et al. 2010). However, the capacity to cope with water stress will likely vary significantly between riparians both because of their individual water resources and institutions and because of state consumption. At root, there is a great deal of uncertainty because of multiple global climate models (Conway 2005). And this uncertainty is often concealed by aggregate metrics and simplistic approaches to water scarcity (Zeitoun et al. 2016). Open cooperation based on reliable data is likely the only solution to sustainable use of the Nile basin.
The Nile is projected to see some reduction in runoff by 2050 (Aaerts et al. 2006; Manabe et al. 2004) or a large increase in runoff (Arnell 2003; Milly et al. 2005). Either scenario will see concomitant increases in water withdrawals because of population growth and increasing demand (Alcamo et al. 2007). The effect of demand should not be underestimated. A 2007 study found that around 90 percent of water stress derived from increasing water withdrawals, while only 10 percent arose from issues of water availability due to climate change (Alcamo et al. 2007). In other words, water demand is a more significant factor than water availability in this case.
However, there are obstacles to measuring water resources, a key part of assessing the risk climate change poses. Data on groundwater sources remains scant (Gaye and Tindimugaya 2019) and traditional metrics of water scarcity rely on mean annual river runoff, occluding high seasonal variability of precipitation and local-scale needs in favour of aggregate indicators (Damkjaer and Taylor 2017). Otherwise said, metrics of water scarcity are poorly calibrated to social needs and physical resources. With this in mind, the idea of making an informed decision about how to mitigate water stress caused by climate change is plagued with difficulty.
Most pressed by the urgency of climate change is probably Egypt, relying on upstream waters from the Nile for over 90 percent of its water resources (Hussein and Grandi 2017). Egypt must contend with highly variable interannual and interdecadal rainfall and river flow, compounded by increasing demand from its own populace as well as growing demand upstream (Conway 2005). Indeed, by 2050, the basin is expected to have a population of nearly one billion and see interannual variability of the Nile flow increase by 50 percent (Siam and Eltahir 2017).
As is clear by now, increasing water stress places further pressure on Nile riparians to secure adequate water resources for their population. This has raised concern over water wars, but need not result in conflict. First is the potential utilisation of groundwater resources, which have a volume 100 times larger than annual renewable freshwater resources in Africa (MacDonald 2012). Indeed, though groundwater resources are unevenly distributed, as relevant here, Egypt and Sudan both have amongst the largest sedimentary aquifers in Africa (MacDonald 2012). Crucially then, groundwater resources provide one avenue of relief for growing water demands downstream and may help alleviate political stress over the Nile too (Gaye and Tindimugaya 2019).
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