A global water scarcity assessment under Shared Socio-economic Pathways – Part 1: Water use

A novel global water scarcityassessment for the 21st century is presented in a two-part paper. In this first pa- per, water usescenarios are presented for the latest global hydrological models. The scenarios are compatible with the socio-economic scenarios of the Shared Socio-economic Pathways (SSPs), which are a part of the latest set of sce- narios on global change developed by the integrated assess- ment, the IAV (climate change impact, adaptation, and vul- nerability assessment), and the climate modeling commu- nity. The SSPs depict five global situations based on substan- tially different socio-economic conditions during the 21st century. Water usescenarios were developed to reflect not only quantitative socio-economic factors, such as population and electricity production, but also key qualitative concepts such as the degree of technological change and overall envi- ronmental consciousness. Each scenario consists of five fac- tors: irrigated area, crop intensity, irrigation efficiency, and withdrawal-based potential industrial and municipal water demands. The first three factors are used to estimate the po- tential irrigation water demand. All factors were developed using simple models based on a literature review and analy- sis of historical records. The factors are grid-based at a spa- tial resolution of 0.5 ◊ 0.5 and cover the whole 21st cen- tury in five-year intervals. Each factor shows wide variation among the different global situations depicted: the irrigated area in 2085 varies between 2.7◊ 10 6 and 4.5◊ 10 6 km 2 , withdrawal-based potential industrial water demand between 246 and 1714 km 3 yr 1 , and municipal water between 573 and 1280 km 3 yr 1 . The water usescenarios can be used for global water scarcityassessments that identify the re- gions vulnerable to water scarcityand analyze the timing and magnitude of scarcityconditions.