Long-Term Global Water Projections Under Climate Change


Global freshwater use has grown over the past century from an estimated annual 580 km3 in 1900 to 3829 km3 in 2000, and continued growth is expected in the 21st century. U.S. Department of Energy scientists at Pacific Northwest National Laboratory, in collaboration with a multi-institutional team, used the Global Change Assessment Model (GCAM) to assess future water demands representing six socioeconomic scenarios. The modeling framework explicitly tracks future water demands for the agricultural (irrigation and livestock), energy (electricity generation, primary energy production and processing), industrial (manufacturing and mining), and municipal sectors. The energy, industrial, and municipal sectors are represented in 14 geopolitical regions, with the agricultural sector further disaggregated into as many as 18 agro-ecological zones within each region. The scenarios showed increases in global water withdrawals from 3710 km3 year−1 in 2005 to 6195–8690 km3 year−1 and to 4869–12,693 km3 year−1 in 2050 and 2095, respectively. Comparing the projected total regional water withdrawals to the historical supply of renewable freshwater, the Middle East exhibits the highest levels of water scarcity throughout the century, followed by India. Water scarcity increases over time in both of these regions. In contrast, water scarcity improves in some regions with large base-year electric sector withdrawals, such as the United States and Canada, due to capital stock turnover and the almost complete phaseout of once-through flow cooling systems. The team concludes that: 1) fresh water availability may be insufficient to meet all future water demands in some regions such as the Middle East and India; and 2) many regions can be expected to increase reliance on nonrenewable groundwater, water reuse, and desalinated water, but they also highlight an important role for development and deployment of water conservation technologies and practices.


Hejazi, M., J. Edmonds, L. Clarke, P. Kyle, E. Davies, V. Chaturvedi, M. Wise, P. Patel, J. Eom, K. Calvin, R. Moss, and S. Kim. 2013. “Long-Term Global Water Projections Using Six Socioeconomic Scenarios in an Integrated Assessment Modeling Framework,” Technological Forecasting and Social Change, DOI: 10.1016/j.techfore.2013.05.006.