Abstract: Data are presented for nitrate, dinitrogen and argon concentrations and 15N14N ratios in groundwater, with radiocarbon ages up to 40,000 yr. for three confined sandstone aquifers in the western Kalahari of South West Africa/Namibia. The nitrate is probably generated within the soil of the recharge areas, and its production rate during the period 3000-40,000 B.P. has remained between 0.5 and 1.6 meq NO−3l−1 of recharge water, with ° 15N between + 4 and + 8‰. Variations in the amount of nitrate and of “excess air” in groundwater recharge are found, and can only reflect changes in the environmental conditions during recharge. They must therefore be caused by the climatic changes that have taken place during the past 25,000 yr.

Abstract: Elevated levels of nitrate occur in phreatic groundwater in the western Kalahari, Namibia. Nitrate in water containing 0.4–3.1 meq NO−3l−1, of widespread occurrence, has δ15N values in the range +4.9 to +8.0‰, suggesting natural derivation from the soil. The sporadic occurrence of very high levels of nitrate (> 4 meq NO−3l−1), which has δ15N between +9.3 to +18.7‰, reflects pollution derived from animal waste. The importance of considering the possible isotopic effects of denitrification, and the significance of leaching in the nitrogen budget of the Kalahari soil, are also discussed.

Abstract: Apart from some notable exceptions, the sound governance of transboundary aquifers (coupled or uncoupled to rivers) is seriously lacking in most regions of the world, despite a highly successful 20-year ISARM initiative. The distinction between regions of water abundance (as in the Haute Savoie–Geneva aquifers) and those of water scarcity (\textless1000 m3/an/capita), as in the Rum-Saq aquifer, ought to be a driver for the urgency in adopting sound governance. In the latter regions, however, such an urgent response faces too many hurdles (institutional, financial, and weak capacity). Climate change, one of the global megatrends (among demography, economic shift, resources stress, urbanization, and novel viruses such as COVID-19), will exacerbate the problem in the coming decade and beyond. This chapter provides an critical perspective on the status of this subsurface asset in 570 or so, domestic and transboundary aquifers of the world (self-identified by country experts), while taking full account of their interconnections, or not, with surface waters. This critical perspective will be grounded in two important factors, first the hiatus in adoption by countries of the evolving international water law and guidance on transboundary aquifers (the Draft Articles, which provide legal pathways for collaboration or eventually dispute resolution), and second the framework of the sustainable development goals (SDG) 6 (clean water and sanitation), which countries have committed themselves to with reference to transboundary waters. The critical perspective finds that despite the lack of momentum in adopting formal global norms, sporadic cooperation and collaboration is continuing and is well received, when delivered methodically through the support of international agencies. The findings of the critical perspective are that even if water-related SDGs will have been achieved across the world, it would contribute precious little to meaningful enhancement of governance of transboundary aquifers, unless they have been explicitly addressed in terms that are tangible to decision makers, such as the impact of disregarding them on the current or future national GDP. The onset of a “new socioeconomic normal” in the aftermath of COVID-19 could further defer meaningful progress, taking the example of Latin America, where a 5% decline has been forecast for 2020. With such declines in the finances of governments, attention to shared aquifer resources may well decline even further. Urgent wise reaction to this possibility must be a priority for the professional science-policy community.