The 2013 ICSU-INQUA-IGCP-GRAPHIC Groundwater @ Global Palaeoclimate Signals (G@GPS) Workshop and Training Course, G@GPS Africa: Long-term recharge of large groundwater basins, was held in Bobole, Mozambique, 14-19 October 2013.

Set in rural Africa, the workshop revolved around identifying rates and times of recharge, for the dual purposes of seeking information about past climates and determining aquifer vulnerability. Participants from 15 countries on five continents discussed a variety of topics, with particular emphasis on development and water resource management issues in African nations.

The topics covered were:

• groundwater-surface water interaction
• strategies for mapping hydrogeologic basins in developing countries
• sustainability assessments
• distinguishing temperature and amount effects in isotopic data
• identifying variations in recharge in large groundwater basins

The meeting also served as a training course on use of isotopes in hydrologic studies, determining groundwater recharge rates from isotopic and geochemical studies, and determining groundwater age. Nearly half of the meeting participants had limited experience of using isotopes as tracers, making this an excellent capacity building opportunity.

Basic theory and application examples were followed by hands-on demonstrations and practice sampling in the conference centre. A day-long trip was organized to provide practical experience sample regional monitoring wells within the critical Maputo groundwater basin. The first well sampled was located in a school yard, much to the amusement of the local children. Combined with additional samples collected after the meeting by meeting participants, these samples will be analysed for a wide range of major and trace elements, and stable and radioactive isotopes to provide one of the first views of groundwater age in a basin that provides water to over 3 million people.

To complete the training course, participants were required to develop a proposal to identify recharge locations and rates in a potential water supply aquifer of interest, with the assistance of more experienced mentors.

Finally, the meeting provided the opportunity to assess progress towards identifying changes in climate and recharge on broad spatial and temporal scales. The G@GPS group is working to collect this information from large groundwater basins with long residence times around the world. Efforts in several large basins were updated, followed by discussions that provide a framework for the group to move forward. Possible cross-basin climate correlations were discussed, although several important issues and gaps exist that still prevent definitive identification of regional/global changes in paleoclimate patterns. Issues include needing better control and understanding of the origin of the oxygen isotopic signature, and better understanding of how mixing within different aquifers would affect correlations. Unfortunately, very little information from aquifers in the Middle East or South America was available. Closing this gap will be part of the focus of the next workshop and training course, which will be held in Argentina in 2014.

Overall, the organizing committee did an excellent job managing a variety of meeting goals and provided an environment conducive to learning and fostering collaboration. IUGG was a sponsor of this workshop through the International Commission on Groundwater (ICGW) of IAHS. Randy Stotler, an isotope hydrogeologist at the University of Kansas in the USA, served as the representative of the ICGW president, Jim Butler, at the meeting and is the author of this report.

Randy Stotler