Groundwater resources and hydroclimatic extremes: mapping global groundwater vulnerability to floods and droughts

Abstract

Extreme hydrological events such as floods and droughts can have devastating impacts on human life, generate economic losses and increase poverty and deprivation. Besides that, their frequency is increasing due to the effects of climate variability and change. Aquifers often offer opportunities for reducing the effects of the impact of these hydrological extremes and contribute to establish emergency drinking water supplies. The global map of groundwater vulnerability to floods and droughts is the result of a joint effort of the projects ‘Groundwater for Emergency Situations’ and the ‘World-wide Hydrogeological Mapping and Assessment Programme’. This map indicates the level of vulnerability of groundwater resources of the earth. It presents the intrinsic vulnerability of groundwater systems and the sensitivity or resistance of those systems to natural disasters. This assessment of global groundwater vulnerability is mainly based on parameters that were globally available: the ‘type of aquifers’ and ‘annual groundwater recharge’. In order to obtain a numerical dimension of vulnerability, individual weighting and a rating scale have been assigned to both these parameters. The final result, called ‘total vulnerability range’, is divided into three categories of groundwater vulnerability: low, moderate and high. Generally, the lower the numerical score, the lower the vulnerability and the higher the level of natural protection of groundwater against hydroclimatic disasters. The resulting categories of vulnerability are indicated on the map by colours. The groundwater vulnerability classification adopted for this map is intended for use as a global overview.