Water scarcity affects 1 in every 3 people on earth (WHO 2010). Water scarcity compares water demand (or water withdrawal) and water availability to estimate the amount of water left over when all demands are fulfilled by available water. It is normally expressed as a ratio (water withdrawal/water availability) and environments with a ratio of 0,4 or more are considered to be in a state of severe water scarcity. Beekman et al. (2009) suggest that Water Scarcity an essential cross-cutting vulnerability issue that should be considered in all development initiatives.
Water scarcity can be portrayed as physical water scarcity – where the limiting factor is an actual physical lack of water due to climatic or other environmental conditions; or economic water scarcity, where there is water, but economic factors influence access to clean or potable water. This can be seen in the following map from the recent United Nations World Water Development Report 3 (World Water Assessment Programme 2009).
Increasing water scarcity across the globe.
Source: World Water Assessment Programme 2009; adapted from Comprehensive Assessment of Water Management in Agriculture 2007
( click to enlarge )
In a region where groundwater is so important, groundwater recharge is key to water availability and water scarcity. Groundwater recharge is defined as the amount of water that contributes to the groundwater table. Recharge is normally considered in terms of the amount of water falling as precipitation that reaches an aquifer, however it also includes water entering from an adjacent aquifer, from surface water sources or injection of water into an aquifer (artificial recharge) (Beekman and Xu 2003).
