Projection of future world water resources under SRES scenarios: water withdrawal

Potential changes in the availability of water resources are one of the greatest concerns relating to global climate warming. Socio-economic developments will also influence water use and demands. This study was conducted to evaluate potential changes in water withdrawals and availability under various socio-economic and climate change scenarios. In the current paper, which presents the first part of the study, future potential water withdrawals are projected according to socio-economic driving factors under the scenarios A1b, A2, B1, and B2 of the Special Report on Emission Scenarios (SRES), which was released for the Fourth Assessment Report on global warming by the Intergovernmental Panel on Climate Change (IPCC-AR4) in 2000. Total world water withdrawal is currently approximately 3800 km(3)/year, and will likely exceed 6000 km(3)/year by 2055, according to all scenarios. Water withdrawal is projected to increase in the future, but change trends largely depend on the socio-economic scenarios. Scenario A2 shows the extreme situation of continuously increasing water withdrawal. The scenario with global cooperation on solutions to social, economic, and environmental issues (Scenario B1) illustrates that society can reach relatively higher economic development by using less water and thus encourages sustainable governance of world water resources. In addition, comparison with other studies is conducted to help us understand the uncertainty range when projecting world water withdrawals according to different methods and assumptions.