A conceptual water budget model is required to “make groundwater visible” in the shared transboundary area of Estonia and Latvia, which doesn’t face any significant water management issues. Despite having a water management agreement since 2003, it wasn’t until 2018 that cooperation on groundwater began. In the EU-WATERRES project, the water balance modelling of the ~9,500 km2 transboundary (TB) area with MODFLOW 6 was performed. Based on budget calculations, the area’s average precipitation is 203 m3 /s, with ~50% (102 m3 /s) of it discharging to the sea as surface water.

Across Africa, given the pressing challenges of climate change and widespread water, food and livelihood insecurity and poverty, there is an ever-increasing expanding role for groundwater in resilience building, especially in borderland communities. This situation is being investigated in several projects and geographies. This paper’s groundwater management analysis was based on literature reviews, key informant interviews (KIIs), and focus group discussions (FGDs) in selected case study areas throughout sub-Saharan Africa.

Worldwide, more than 400 transboundary aquifers (TBAs) have been identified. Only a small number of these aquifers have been assessed in detail. Consequently, little is known about (potential) transboundary impacts. Changes in transboundary groundwater fluxes can indicate potential transboundary impacts as groundwater abstractions can affect such fluxes, indicating potential risks of transboundary contamination.

The beneficial groundwater use in the Southern African Development Community (SADC) is well documented. Groundwater plays a vital role in the freshwater supply mix and, in some cases, is the only source of freshwater, especially in the arid region of SADC. However, the management of this resource is hampered by numerous challenges, such as lack of data, limited tools to leverage available data, lack of resources, institutional mismanagement, and climate change, amongst others.

The so-called apparent increase of transmisivity (T) or hydraulic conductivity (K) with scale is an artifact and does not exist in the field. The reason for the apparent increase of T with scale is due to the use of the “not applicable” random log Gaussian stochastic models that are used by geohydrologists. In the petroleum field, where deterministic methods are applied, the apparent increase of T with aquifer volume does not occur.

The International Association of Hydrogeologists and UNESCO's International Hydrological Programme have established the Internationally Shared (transboundary) Aquifer Resource Management (ISARM) Programme. This multiagency cooperative program has launched a number of global and regional initiatives designed to delineate and analyze transboundary aquifer systems and to encourage riparian states to work cooperatively toward mutually beneficial, sustainable aquifer development and management.

The UNESCO-IHP initiated a project on “Governance of Groundwater Resources in Transboundary Aquifers” in 2013. Three aquifers were selected for case studies: Trifinio (Central America), Pretashkent (Central Asia), and the Stampriet Transboundary Aquifer System (STAS) in southern Africa shared between Botswana, Namibia and South Africa. The project aimed to conduct a detailed assessment of the characteristics, current state and management of transboundary aquifers and to lay the foundations for a multi-country consultation body.