Defining Renewable Groundwater Use and Its Relevance to Sustainable Groundwater Management

Groundwater systems are commonly defined as renewable or non‐renewable based on natural fluxes of recharge or on estimates of aquifer storage and groundwater residence time. However, we show here that the principle of capture (i.e., how recharge and discharge change due to pumping) challenges simple definitions so that a groundwater system cannot be renewable or non‐renewable in and of itself, but only with reference to how the groundwater is being used. We develop and propose more hydraulically informed definitions for flux‐renewable and storage‐renewable groundwater use, and a combined definition that encompasses both the flux‐based and storage‐based perspectives such that: renewable groundwater use allows for dynamically stable re‐equilibrium of groundwater levels and quality on human timescales. Further, we show how a matrix of combinations of (a) the ratio of pumping rate to the maximum rate of capture along with (b) the response or recovery timescales implicit in this definition, leads to a useful four‐quadrant framework for characterizing groundwater use, illustrated using case studies from aquifers around the world. Renewable groundwater use may inform pathways to groundwater sustainability, which encompasses a broader set of dimensions (e.g., socio‐political, economic, ecological and cultural) beyond the scope of groundwater science. We propose that separating physically robust definitions of renewable groundwater use from the inherently value‐based language of sustainability, can help bring much needed clarity to wider discussions about sustainable groundwater management strategies, and the role of groundwater science and scientists in such endeavors

Mammalian biogeography and the Ebola virus in Africa

Ebola virus is responsible for the fatal Ebola-virus disease (EVD). Links between EVD outbreaks in Africa and 3 chiropteran species, presumed to be reservoirs for the Ebola virus, have been suggested, but discussions are still on-going. There is also evidence of significant virus spillover among mammal species not suspected to be natural hosts (e.g. chimpanzees, gorillas and duikers). We mapped the potential distribution of the Ebola virus in Africa based on both environmental and zoogeographic descriptors. We employed distribution modelling using the Favourability Function, alongside a complement of biogeographic approaches including chorotype analysis. We obtained a significantly well-calibrated model defining the distribution of environmentally favourable areas for the presence of Ebola virus, which was outperformed by a model determining favourable areas according to mammalian biogeography. Finally, we built a model in which the combined landscape and mammalian distribution types better explained the distribution of Ebola virus independent of human-to-human transmissions. Our findings show that the core area for the virus is associated with infections of known animal origin, but surrounded by areas where human infections of unknown source were found. This difference in the association between human and animals and the virus may offer further insights to better understand how EVD can spread, as well as providing the basis for an early warning system based on where human contact with multiple animal species may occur. We propose a biogeographically-justified list of at least 64 mammal species whose link with Ebola virus is worth investigating

Global Groundwater Modeling and Monitoring: Opportunities and Challenges

Groundwater is by far the largest unfrozen freshwater resource on the planet. It plays a critical role as the bottom of the hydrologic cycle, redistributing water in the subsurface and supporting plants and surface water bodies. However, groundwater has historically been excluded or greatly simplified in global models. In recent years, there has been an international push to develop global scale groundwater modeling and analysis. This progress has provided some critical first steps. Still, much additional work will be needed to achieve a consistent global groundwater framework that interacts seamlessly with observational datasets and other earth system and global circulation models. Here we outline a vision for a global groundwater platform for groundwater monitoring and prediction and identify the key technological and data challenges that are currently limiting progress. Any global platform of this type must be interdisciplinary and cannot be achieved by the groundwater modeling community in isolation. Therefore, we also provide a high-level overview of the groundwater system, approaches to groundwater modeling and the current state of global groundwater representations, such that readers of all backgrounds can engage in this challenge