Progress in Cooperation on the Senegal-Mauritanian Aquifer Basin

Progress is currently underway to ensure an appropriate legal and institutional format for the joint management of the Senegal-Mauritanian Aquifer Basin (SMAB), a crucial transboundary water resource shared by The Gambia, Guinea Bissau, Mauritania and Senegal.  The Gambia (2023), Guinea Bissau (2021) and Senegal (2018) are parties to the Convention on the Protection and use of Transboundary Watercourses and International Lakes, and as such, support is being provided by the United Nations Economic Commission for Europe (UNECE) for the strengthening of cooperation between the states sharing the aquifer basin. It is expected that discussions will culminate in official announcements during the fourth quarter of 2024. 

The initiative dates back to 2020, when the Regional Working Group for Transboundary Cooperation on the SMAB was established.  In September 2021, facilitated by UNECE, the Geneva Water Hub, and the International Groundwater Resources Assessment Centre, Ministers of the Gambia, Guinea Bissau, Mauritania and Senegal met in Geneva and signed a joint declaration to advance cooperation on the Senegal-Mauritanian Aquifer Basin (SMAB).

In terms of this agreement, a permanent mechanism will be established for the cooperative management of the aquifer system, including both a legal and an institutional framework for cooperation.

This latest step in transboundary cooperation between the countries builds on the extensive experience with transboundary cooperation by Senegal, the Gambia, Guinea Bissau and Guinea in the context of the Gambia River Basin Development Organisation (OMVG) and between Guinea, Mali, Mauritania and Senegal in the context of the Organisation for the Development of the Senegal River (OMVS). The convention establishing the OMVG, was signed in 1978.  Before that, in 1972, the states sharing the waters of the Senegal River had signed a convention creating the OMVS and empowering it to promote and coordinate studies and development work as well as technical and economic missions relating to the joint management of water resources. 

The institutional governance envisaged in the framework of the SMAB is based on the OMVS and OMVG models, which have been a resounding success in terms of transboundary cooperation of shared river basins. these models are based on the sharing of the benefits derived from the common management of water resources by the riparian countries. Given that the aquifer covers a geographical area that includes parts of both river basins that make up the OMVS and OMVG, it was proposed that the two basin authorities join forces for a joint management of the SMAB. This management model is a first and could, if successful, be replicated for the other aquifers in the sub-region and in the whole of Africa where most of the large aquifers are transboundary

The SMAB is the largest aquifer in the West African region, covering a total area of some 335 000 km ², underlying most (84%) of the territory of Senegal, 27% of the territory of Guinea Bissau, 14% of the territory of Mauritania as well as the whole territory of the Gambia. The river basins managed by the OMVS and the OMVG cover 32% and 18% respectively of the SMAB. This raises some questions about the institutional locus that should be chosen to ensure the effective management of these vast resources.

It is estimated that 16 million people live in the region covered by the SMAB, and that 80 % of the population of the countries involved depend on groundwater for their livelihoods and domestic needs. Groundwater is a crucial source of water in rural areas as well as being a major source of water for cities, and it is an important fallback resource in the context of highly variable rainfall conditions.  As climate change (through increased temperatures and frequency of droughts and floods) has become a reality in the region, the joint use of surface water and groundwater is becoming a necessity. The conjunctive use of surface water and groundwater refers to the coordinated management and utilisation of both surface water (such as rivers, lakes, and reservoirs) and groundwater (water stored underground in aquifers) resources. This integrated approach aims to optimize the overall water supply, enhance water security, and ensure sustainable water resource management.

Judicious conjunctive use of water resources requires a careful assessment of groundwater resources, availability and sustainable yield. Given the highly variable nature of precipitation in the West African region, groundwater appears at first glance to be a reliable alternative, but this is not always the case: large and concentrated water demand such as that from large irrigation schemes is usually supplied from surface water storage.  

This is in part due to the fact that groundwater aquifers seldom offer the large storage capacity or rapid infiltration rates to be able to absorb large volumes of floodwaters in a short period of time and are unable to return them as significant discharge per unit production system of well or borehole.

Secondly, interventions to increase surface water storage and distribution networks tend to be associated with higher political visibility, while also providing a point of entry for private contractors and other multiplier effects in the economy. By contrast, groundwater projects tend to be much more geographically dispersed and less prominent or visible.

The cooperative agreement on the SMAB is the first in West Africa and one of only seven transboundary agreements in the world that are focused on groundwater resources. There are some 200 international agreements in existence on the shared use of transboundary waters, but most of these are primarily focused on the sharing of surface water resources.