The Congo Basin (CB), home to the world’s second-largest river basin and tropical rainforest (Laraque et al., 2020), holds significant groundwater resources (Kasongo-Numbi, 2008; MacDonald et al., 2012; Tourian et al., 2023). Despite the abundance of surface water within the region, groundwater is a crucial source of freshwater for the vast majority of the CB’s population. It plays a vital role in sustaining human consumption, particularly for the rural population, also, for ecosystems and agriculture even though the latter is still rainfed. Domestic water use constitutes the first sector that withdraw the large amount of groundwater in the basin. The water withdrawal is projected to grow significantly due to the human population that is expected to double by 2050 in Africa (Partow, 2011, United Nations, 2019). Additionally, considering the emerging importance of the global change due to climate change and environmental alterations that have already affected surface water within the basin (Reed and Miranda, 2007; Wongchuig et al., 2023), groundwater is likely to become a critical resource for future development in the region. Therefore, there is an urgent need for a sustainable groundwater management. However, groundwater management in the CB faces numerous challenges.

Can this challenge be solved using space technologies and data? If so, which one?

Yes, Earth Observations, particularly satellite-based remote sensing such as Gravity Recovery and Climate Experiment (GRACE) data, surface water elevation from satellite altimetry, satellite precipitation data, and in situ water level from piezometer and river discharge

Has this problem been acknowledged in the past?

Yes, this problem has been already acknowledged in the past by NGOs, particularly the United Nations Environment Programme (UNEP) in a technical report that presents Water Issues in the Democratic Republic of the Congo (UNEP, 2011)

Expected time frame to develop solution

6 months to setting up a groundwater storage dataset (ongoing work) • 3 years installing groundwater monitoring system and starting recording of almost two hydrological seasons • 2 years to generate the knowledge using the above satellite and in situ data

(Potential) Consequences if no action happens

• Without proper scientific knowledge, groundwater extraction could happen unsustainably. This can lead to over-extraction of aquifers, which would reduce groundwater availability over time
• In the absence of monitoring, the recharge rates of aquifers may not be well understood, leading to groundwater depletion that could take decades or centuries to recover.
• Groundwater is a critical water source for rural and urban populations across the Congo Basin. Without data to manage it, future demand could outpace available supplies

9.What are physical requirements needed for a solution?

Several physical requirements are necessary to establish a robust monitoring, research, and management system. These requirements span infrastructure, technology, human resources

1. Groundwater Monitoring Infrastructure made of Groundwater Monitoring Wells (Borehole loggers and piezometers to measure groundwater levels) and Satellite-Based Monitoring (GRACE and SWOT for monitoring groundwater storage variations and surface water interactions). Generating in situ and remote sensing data will enable to develop Modeling Tools (MODFLOW, SWAT, VIC).
2. Data Collection and Management Systems that will help to Collect groundwater-related data (e.g., water levels, quality, recharge rates) from multiple sources.
3. Capacity Building will allow to build local capacity for groundwater research and management. The focus can be on students at Master and doctorate level for their research project.

References and data sources

Kasongo-Numbi, K. (2008). Eaux et forêts de la république démocratique du Congo -... - Librairie Eyrolles (L’Harmattan, Ed.). https://www.eyrolles.com/Sciences/Livre/eaux-et-forets-de-la-republique…

Laraque, A., N’kaya, G. D. M., Orange, D., Tshimanga, R., Tshitenge, J. M., Mahé, G., Nguimalet, C. R., Trigg, M. A., Yepez, S., & Gulemvuga, G. (2020). Recent budget of hydroclimatology and hydrosedimentology of the congo river in central Africa. Water, 12(9). https://doi.org/10.3390/w12092613

MacDonald, A. M., Bonsor, H. C., Dochartaigh, B. É. Ó., & Taylor, R. G. (2012). Quantitative maps of groundwater resources in Africa. Environmental Research Letters, 7(2), 024009. https://doi.org/10.1088/1748-9326/7/2/024009

Partow, H. (2011). Water Issues in the Democratic Republic of the Congo Challenges and Opportunities Technical Report United Nations Environment Programme. http://www.unep.org

Reed, E., & Miranda, M. (2007). Assessment of the Mining Sector and Infrastructure Development in the Congo Basin Region. http://www.panda.org/mpo

Tourian, M. J., Papa, F., Elmi, O., Sneeuw, N., Kitambo, B., Tshimanga, R. M., Paris, A., & Calmant, S. (2023). Current availability and distribution of Congo Basin’s freshwater resources. Communications Earth & Environment 2023 4:1, 4(1), 1–13. https://doi.org/10.1038/s43247-023-00836-z