The Disappearing Oases of the Sahara

Discussing the consequences of climate change to water resources is often not the most 'flashy' of topics, however highlighting the disappearing oases in the Sahara can be a way to communicate the fundamentals of groundwater science.

The IPCC reports on climate change have consistently identified the periphery of the Sahara Desert as vulnerable to large-scale environmental change due to continuous temperature increases (IPCC, 2014).

As the temperature increases, the water system in the Sahara desert is being altered at an alarming rate and the impacts are visible through a rapidly changing environment. Desertification rates are increasing, ephemeral rivers are drying up faster and most notably, oases are disappearing (Geriesh et al, 2015).

Figure 1: Annual observed temperature & precipitation changes from the 20th-21st century across Africa (IPCC, 2014).

As seen in figure 1, the Sahara desert has seen a wide-scale warming trend throughout the 20th and early 21st century, coinciding with some areas of lower than average precipitation. In particular, the Western Sahara has seen the most extreme warming and the consequences are visible, particularly on the boundary between the anti-Atlas mountains and the Sahara desert. The Draa valley is home to many subsistence and agricultural communities relying on the Draa river and groundwater to sustain their crops and oases, however recent climactic trends threaten the sustainability of these practices (Medomed, 2020). In particular, desertification has increased, and lower groundwater levels have rendered reforestation methods ineffective as a method to combat the spread of the desert. Higher temperatures also result in more instances of salinisation as the evapotranspiration rates increase, causing problems for both the subsistence and exporting agricultural industry.

Figure 2: Projected worst-case scenario and vulnerability to biome changes for Africa. Note the distinct high vulnerability level of northwestern Africa, with the anti-Atlas region highlighted for desertification risk (IPCC, 2014).

Due to the coupling of lower groundwater levels, decreasing and irregular rainfall, the local oases of the anti-Atlas region are drying up. As seen in figure 2, the western periphery of the Sahara desert is extremely vulnerable to environmental change and this is mainly driven by the climactic changes that have occurred in this region over the past century. This is also likely to have a large human impact and if trends continue, up to 230,000 people will be displaced from the region (DW, 2020).