Abstract
Abstract. A novel global water scarcity assessment for the 21st century is presented in a two-part paper. In this first paper, water use scenarios 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 scenarios on global change developed by the integrated assessment, the IAV (climate change impact, adaptation, and vulnerability assessment), and the climate modeling community. The SSPs depict five global situations based on substantially different socio-economic conditions during the 21st century. Water use scenarios 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 environmental consciousness. Each scenario consists of five factors: irrigated area, crop intensity, irrigation efficiency, and withdrawal-based potential industrial and municipal water demands. The first three factors are used to estimate the potential irrigation water demand. All factors were developed using simple models based on a literature review and analysis of historical records. The factors are grid-based at a spatial resolution of 0.5° × 0.5° and cover the whole 21st century in five-year intervals. Each factor shows wide variation among the different global situations depicted: the irrigated area in 2085 varies between 2.7 × 106 and 4.5 × 106 km2, withdrawal-based potential industrial water demand between 246 and 1714 km3 yr−1, and municipal water between 573 and 1280 km3 yr−1. The water use scenarios can be used for global water scarcity assessments that identify the regions vulnerable to water scarcity and analyze the timing and magnitude of scarcity conditions.
Highlights
All societal and economic activities depend on water
Potential irrigation water demand is reported in the accompanying paper (Hanasaki et al, 2013), as global hydrological simulations are required for its estimation
The populations assumed in the Shared Socio-economic Pathways (SSPs) and the five reports were different, but no population adjustment was performed in this study
Summary
All societal and economic activities depend on water. The rapid and continuous growth of population and economic activity, mainly in developing countries, is increasing water use globally. A number of studies have assessed the impact of global changes (i.e. socio-economic and climatic change) on water use and availability (Vorosmarty et al, 2000; Alcamo et al, 2003a, b, 2007; Arnell, 2004; Oki and Kanae, 2006). These studies have identified water-scarce regions in baseline periods by compiling statistical data for water use and availability and have projected future scarcity using numerical models. Potential water demand is the estimated water use accompanying human activities regardless of water availability
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