Top 3 Threats to the Shallow Groundwater in Sub-Saharan Africa

What is a shallow aquifer?

Groundwater occurs in aquifers that can be found either at shallow superficial or at deeper depths.   The definition of whether an aquifer is shallow or deep varies regionally as well as whether several other aquifers are found below the uppermost one. In this article, the shallow aquifers refer to groundwater resources that are <50 m deep. Such aquifers exist both in wet regions and also in arid and semi-arid areas of Sub-Saharan Africa.

The top three threats to the shallow aquifers in Sub-Saharan Africa region include; contamination and pollution, climate variability, and overexploitation.

1. Contamination and pollution

People live where there is water. With this regard, the shallow aquifers in Sub-Saharan Africa have attracted numerous populations within their localities. This tremendous population growth in areas with shallow aquifers has seen them grow into big cities and are expanding by the day.  As much as it is a cheap resource to exploit, it is the most vulnerable source of groundwater, and the price of not being able to use it due to pollution challenges is beyond expectations. The increased populations require increased food supply giving rise to the emergence of irrigated agriculture in the SSA. According to FAO, the irrigated land in Africa is 7%, and 3.7% is within Sub-Saharan Africa and is mostly along permanent rivers.  The use of agrochemicals leading to leakage of harmful chemicals such as heavy metals into the groundwater, leading to groundwater contamination. Another source of aquifer contaminants is poor sanitation and hygiene in urban areas.   The provision of social amenities in Africa does not match the population growth in most cases resulting in the open defecation practice. Besides, developing pit latrines on top of aquifers can be compared to bringing a poisonous spoon closer to a child’s mouth.

2. Climate variability

Do you know that changes critical aspect of the climate such as rainfall patterns and temperature affects our groundwater? The important processes of the hydrological cycle help to explain how raindrops travel through the sub-surface into the aquifer. This process is referred to as groundwater recharge. The groundwater we use today is a result of the infiltration of rainfall several years ago, especially in the deep groundwater. However, most recharge of the shallow aquifers in Sub-Saharan Africa is either due to direct recharge by recent rainfalls or by permanent rivers in arid and semi-arid areas.   As a result of the increased rainfall variability, floods and droughts have increased the dependence on groundwater in the region. During the floods, most of the surface water alternatives become contaminated and are not useful until several weeks after the flood events. Although recharge of the shallow aquifers occurs during this time, several pollutants are transported from the subsurface into the aquifer by the infiltrating water. This scenario is elevated in urban shallow aquifers.   During the prolonged droughts, the water table of the shallow aquifers in arid and semi-arid areas lowers, and some wells dry up as a result. At the same time, the water shortage renders groundwater the only source of water supply posing a danger of overexploitation. The elevated temperatures cause intense evaporation and may lead to increased salinity in the aquifers. Thus, climate variability influences both water quality and quantity.

3. Overexploitation

Sub-Saharan Africa is experiencing rapid population growth. Approximately 250 million people, 40% of the total population in the region, live in urban centers. Due to limited surface water resources, groundwater is the primary source of most municipal water supplies. Research has shown that the rate of groundwater abstraction is less than the rate of groundwater recharge. Thus, there an impending danger of aquifer depletion from overexploitation. Increased industrialization in the region also elevates the water demand beyond the domestic and agricultural levels. Evidence has shown that most cities are situated on top of aquifers, and direct recharge by rainfall is limited by tarmacked surfaces, buildings, and pavements. Thus, the stressed shallow aquifers in Sub-Saharan Africa needs urgent attention concerning overexploitation.

To ensure the future generation is guaranteed their right to clean water, thoughtful considerations need to be in place regarding settlement, development, and industrialization. Expert knowledge needs to be sought to establish the vulnerability status of the shallow aquifers for protection and sustainable management.