The measurement of water scarcity: Defining a meaningful indicator

Abstract

Metrics of water scarcity and stress have evolved over the last three decades from simple threshold indicators to holistic measures characterising human environments and freshwater sustainability. Metrics commonly estimate renewable freshwater resources using mean annual river runoff, which masks hydrological variability, and quantify subjectively socio-economic conditions characterising adaptive capacity. There is a marked absence of research evaluating whether these metrics of water scarcity are meaningful. We argue that measurement of water scarcity (1) be redefined physically in terms of the freshwater storage required to address imbalances in intra- and inter-annual fluxes of freshwater supply and demand; (2) abandons subjective quantifications of human environments and (3) be used to inform participatory decision-making processes that explore a wide range of options for addressing freshwater storage requirements beyond dams that include use of renewable groundwater, soil water and trading in virtual water. Further, we outline a conceptual framework redefining water scarcity in terms of freshwater storage.Electronic supplementary materialThe online version of this article (doi:10.1007/s13280-017-0912-z) contains supplementary material, which is available to authorized users.

A First Estimation of County-Based Green Water Availability and Its Implications for Agriculture and Bioenergy Production in the United States

“…Selecting a suitable WAI for a particular study could be confusing because a wide range of "water availability", "water stress", or "water scarcity" indices exist [37][38][39][40]. The three terms have been used frequently and interchangeably in the literature either to label a metric or to describe water resource problems [39].…”

“…For instance, all areas with a per-capita water resource less than 1700 m 3 per year would be considered water scarce. To address that problem, various metrics based on use-to-availability ratios (Table 1), which incorporate spatial varying water demand from multiple economic sectors, have been proposed during the second wave of water resource assessments [40]. In general, a country or region is considered water scarce if annual withdrawals are higher than 20% of annual freshwater supply and severely water scare if this ratio exceeds 40% [40,50,51].…”

“…To address that problem, various metrics based on use-to-availability ratios (Table 1), which incorporate spatial varying water demand from multiple economic sectors, have been proposed during the second wave of water resource assessments [40]. In general, a country or region is considered water scarce if annual withdrawals are higher than 20% of annual freshwater supply and severely water scare if this ratio exceeds 40% [40,50,51]. Falkenmark [6] and Kummu et al [5] suggest that per-capita water availability metrics are helpful to identify "water shortage" driven by population growth, whereas use-to-resource-based indices measure "water scarcity" due to high demand relative to availability.…”

Uncovering the Green, Blue, and Grey Water Footprint and Virtual Water of Biofuel Production in Brazil: A Nexus Perspective

“…To estimate water scarcity, we used Raskin's definition of water scarcity [34] as the ratio of total water withdrawal (TWW) to total water availability (TWA). The water scarcity index (WSI) is thus given by WSI = TWW/TWA.…”

Resilience Dynamics of Urban Water Supply Security and Potential of Tipping Points

“…Common assessments of urban water supply security quantify the average per capita water availability, whether natural or captured (Damkjaer & Taylor, 2017;Floerke et al, 2018;Jenerette & Larsen, 2006;McDonald et al, 2011McDonald et al, , 2014Padowski & Jawitz, 2012), or focus on the sections of urban society living in water poverty (Cho et al, 2010;Eakin et al, 2016;Juran et al, 2017;Srinivasan et al, 2010;Sullivan, 2002; ©2019. The Authors.…”