Adaptation to Environmental Change: Dams

Dams are a common adaptation option to tackle increased rainfall variability and dry events under climate change. There are two large dams in the SRB: the Manantali Dam and the Diama Dam. The Manantali Dam is primarily used for regulating river flow, and it is also utilised for hydropower generation. The Diama Dam was originally built for blocking sea water intrusion at the river mouth, but now acts as a reservoir to provide water for perennial irrigation because of heightened agricultural demands (Dumas et al., 2010).

Evaluating the sustainability of dams

In a report commissioned by the OMVS, the dams proved successful in increasing water levels in the SRB, maintaining river flow even during dry seasons, hence providing water availability for irrigation throughout the year. In the SRB river valley, irrigated land increased from merely 20 ha in 1974 to 18000 ha in 1988 (DeGeorges, 2006). Specifically, irrigated rice cultivation was promoted, and there was a large increase in rice farming yields since the operation of the dams.

  

Mean monthly water levels in the Senegal River recorded in Podor and Matam before (1980-1983) and after (1990-2017) the construction of dams.

However, the sustainability of the dams remains questionable. First, there are numerous environmental problems associated with the dams. As dams store water, regulate flows and consume water for irrigation schemes, it reduces the overall discharge downstream (Nielsen et al., 2020). Consequently, flood extent declines and leads to shrinking of wetlands; the area of wetlands in the SRB decreased by around 12000 ha because of the dams (Manikowski and Strapasson, 2016). Furthermore, dams result in stagnant water which encourages the expansion of invasive plant species (Manikowski and Strapasson, 2016). A case in point in the SRB is the Djoudj National Bird Sanctuary, a UNESCO World Heritage site that serves as a wintering ground or habitat for over 300 million birds. It has suffered from reduced flood extent and invasion of Salvinia molesta, which led to a decrease in biodiversity (Diouf, 1998; Degeorges and Reilly, 2007).

Moreover, the dams bring about negative social impacts, one of which is displacement. In an article published by Yale Environment 360, the author argues that big water projects helped induce Africa’s Migrant Crisis, using the Manantali Dam as an example to illustrate the loss of traditional livelihoods forcing people to leave their villages. With a stark decline in floodplains, fisheries and pastures for traditional agricultural practices (Degeorges and Reilly, 2006), it caused a displacement of over 10000 people behind the Manantali Dam (Degeorges and Reilly, 2007). In addition, stagnant water together with water spills from irrigation schemes foster outbreaks of waterborne diseases such as malaria and diarrhea, posing threats to the public health and wellbeing in the SRB (Manikowski and Strapasson, 2016).

Therefore, while dams in the SRB are effective in promoting reliable agricultural development, the significant environmental and social drawbacks highlight the need for an improved approach that is more sustainable environmentally and socially.