Modeling global water use for the 21st century: Water Futures and Solutions (WFaS) initiative and its approaches

Abstract

Abstract. To sustain growing food demand and increasing standard of living, global water use increased by nearly 6 times during the last 100 years and continues to grow. As water demands get closer and closer to the water availability in many regions, each drop of water becomes increasingly valuable and water must be managed more efficiently and intensively. However, soaring water use worsens water scarcity condition already prevalent in semi-arid and arid regions, increasing uncertainty for sustainable food production and economic development. Planning for future development and investments requires that we prepare water projections for the future. However, estimations are complicated because the future of world's waters will be influenced by a combination of environmental, social, economic, and political factors, and there is only limited knowledge and data available about freshwater resources and how they are being used. The Water Futures and Solutions initiative (WFaS) coordinates its work with other on-going scenario efforts for the sake of establishing a consistent set of new global water scenarios based on the Shared Socioeconomic Pathways (SSPs) and the Representative Concentration Pathways (RCPs). The WFaS "fast-track" assessment uses three global water models, namely H08, PCR-GLOBWB, and WaterGAP. This study assesses the state of the art for estimating and projecting water use regionally and globally in a consistent manner. It provides an overview of different approaches, the uncertainty, strengths and weaknesses of the various estimation methods, types of management and policy decisions for which the current estimation methods are useful. We also discuss additional information most needed to be able to improve water use estimates and be able to assess a greater range of management options across the water-energy-climate nexus.

Water use in a heavily urbanized delta : scenarios and adaptation options for sectorial water use in the Pearl River Basin, China

“…TC estimation is consistent with the WFaS approach, which quantifies annual technological improvement rates for each of the 11 data.worldbank.org combinations of SSPs and HE classifications using a range of historical observations (Wada et al 2016) .…”

“…The estimated global average annual water used for production was 9087 billion m 3 during the period 1996-2005, of which 8363 billion m 3 or 92% was used for agricultural production, 400 billion m 3 (4.4%) was used for industrial production, and 324 billion m 3 (3.6%) was used for domestic uses (Hoekstra and Mekonnen 2012). By 2050, the industrial water use is projected to have doubled compared to the water use in 2010, whereas the domestic water use is foreseen to increase 50% -250% during the same period (Wada et al 2016).…”

“…The water use scenarios for the upstream regions, i.e. Guangxi, Guizhou, Yunnan, and Guangdong without the delta, are generating using the national assumptions and planning targets for China during the period 2010-2050 (Wada et al 2016). Quantitative assumptions for China's population and GDP growth are compiled from the SSPs database 12 , the IIASA-VIC v9 and OECD Env-Growth v9, respectively.…”

“…In the WFaS initiative, the SSP storylines have been enriched with critical water dimensions that will affect sectorial water uses. This has provided a set of water-extended SSP narratives including qualitative changes in the diverse drivers of societal water use, which were translated into a set of quantitative assumptions for implementation in the multi-model assessment (Wada et al 2016) .…”

“…A recent work was carried out by the Water Futures and Solutions initiative (WFaS; http://www.iiasa.ac.at/WFaS), which is a collaborative, stakeholder-informed effort applying systematic global scenario analysis to identify future hotspots of water insecurity. The WFaS developed a set of water-use scenarios consistent with the SSPs and RCPs, and estimated the global sectorial water use using a state-of-the-art multi-model framework (Wada et al 2016) (The term "water use" in the WFaS assessment refers to water withdrawal.…”