The importance of water to agriculture and food security. Water is an essential input for agriculture and food production. Ensuring it is available where and when needed is a major challenge, however, since the absolute volume in particular locations can be both limited and variable. Rainfall follows seasonal patterns, which typically provide communities with adequate water supplies for agriculture in some months but not in others. In many places, climate change is making rainfall more erratic. The typical response is to store and manage water, so that it can be made available at times of the year when it is normally scarce. Increasingly, such efforts take into account both surface water – which has historically received highest priority – as well as groundwater. The latter often presents a more sustainable option, as it is less vulnerable to climate change impacts and if used appropriately, can serve as “natural infrastructure” for water storage.

International borders confound attempts to optimally store, manage and use water in Africa. Transboundary river basins, which cover more than 60 percent of Africa’s land area, have been the focus of considerable attention and cooperative effort (Figure 1). Recent work has delineated more than 70 transboundary aquifers in Africa, including more than 30 in the Southern African Development Community (SADC). International borders constrain efforts to improve the management of this vital resource, since policies and water use in one part of a watercourse may limit its availability – or reduce its quality – in another part. Failure to find cooperative approaches for managing shared waters can lead to strained relations between states. This also results in missed opportunities to strengthen food and water security, together with enhanced resilience in the face of water-related risks. Cross-border cooperation is therefore critical for capturing shared ground and surface water resources more effectively to improve agricultural production and attain other development objectives.

Expanding cooperation in transboundary groundwater management or going it alone? Cooperation oriented toward surface water, often at a basin-level, is widespread in Africa. Cooperation in the management of transboundary aquifers is less common. Groundwater-focused cooperation has typically followed one of two paths: (1) expanding the mandates of surface-water river basin organizations (RBOs) to cover groundwater or (2) fostering transboundary cooperation for specific aquifers. While both approaches have merit, each also has limitations. Concerning the first, the fundamental question is whether the scale and extent of a surface water RBO can permit it to cover both surface and groundwater. The management of transboundary aquifers often entails decisions and actions that respond to unique local issues. Since RBOs are generally oriented to facilitating cooperation on a much larger scale, it may simply be impractical for them to take on this additional responsibility. As for the second option, institutions and treaties pertaining to specific aquifers may be effective where surface water is insignificant (as in the Sahara Desert). In most cases, however, institutions focused solely on groundwater may be ill prepared to manage its interactions with surface water.

Conjunctive management of shared waters: A third way? It may ultimately be best to think beyond the binary set of options presented above. Recent experience from SADC indeed suggests that it may be wise to scale up groundwater cooperation in the context of a systems approach where multiple sources of water and ecosystems are considered together and managed in conjunction. Nonetheless, guidance on appropriate institutional frameworks for conjunctive management of diverse water sources in a transboundary context – and the scale to which they may apply – do not exist. This reality is somewhat paradoxical given that the most technically sound manner to manage water is to consider all relevant water sources and manage such sources conjunctively for optimal benefit. Part of the problem is that the issue of scale in managing transboundary ground-surface systems is not straightforward. While surface water management lends itself to basin frameworks, groundwater requires a focus on aquifers. The scale of conjunctive surface-groundwater management, in contrast, requires innovative approaches that respond to issues of concern to riparian and aquifer-sharing states.

A new project – Conjunctive Management of Transboundary Waters in SADC. In response to this challenge, the International Water Management Institute (IWMI) has embarked on a new project funded by USAID, which will strengthen conjunctive water management across borders in the SADC region. The project will work simultaneously in three shared watercourse/aquifer systems of the region shown in Figure 2: the Ngotwane River/Ramotswa Aquifer System (Botswana and South Africa); the Limpopo River/Tuli-Karoo Aquifer System (Botswana, South Africa and Zimbabwe); and the Shire River/Aquifer System (Malawi and Mozambique). Researchers will focus on determining the baseline conditions, identifying policy and technical solutions, and facilitating stakeholder engagement, aimed at achieving endorsement and implementation of these solutions. The project will also synthesize experiences from the three systems to develop guidelines that can be applied elsewhere for conjunctive management of shared water systems.