Fig. 1: Schematic diagram depicting four different patterns used to identify the FirstWS and EndWS.
From: Timing the first emergence and disappearance of global water scarcity
a The ‘Never WS’ condition denotes the absence of water scarcity (WS) during the entire study period (i.e., nonexistent FirstWS and EndWS). b The ‘Always WS’ refers to the condition where WS occurred before the 20th century (i.e., FirstWS before 1901) and lasted the entire period; an EndWS cannot be identified. c The ‘Intermediate WS Type I’ pattern corresponds to a condition whereby WS occurs intermittently yet continues until the late phase of the study period, i.e., an EndWS can not be identified within the study period. d In the ‘Intermediate WS Type II’ condition, the water scarcity also occurs intermittently but it disappears in the late phase of the study period; both its FirstWS and EndWS can be identified. The “FirstWS” is defined as the initial year when the per-capita water availability at the grid scale falls below the 1000 m3/person/year threshold for a minimum of five consecutive years between 1901 to 2090. The “EndWS” is defined as the first year when the water scarcity is relieved for a continuous period of five years or more, and the scarcity-free state remains until the end of the 21st century.
