Alcamo et al., 2003
This excerpt has been prepared by Mareen E. Hofmann in the context of
the ADAM "Meta-analysis of impacts, vulnerability and adaptation (CCIVA)
assessments in Europe". Please note that the corresponding study was not
itself a part of the ADAM project!
Alcamo, J.; Doll, P.; Heinrichs, T.; Kaspar, F.; Lehner, B.; Rosch, T.; Siebert, S.: Global estimates of water withdrawals and availability under current and future business-as-usual conditions. Hydrological Sciences Journal, 48: 339-348; 2003
You should take a look at this study if you are interested in:
economic sector: Technology
environmental issue: Water resources
One sentence summary:
The paper presents global estimates of water availability, water withdrawals, and other indicators on the river-basin scale by applying the WaterGAP 2 model to the current and future water situation; main results include that currently about one-fourth of the world river basin area might be considered to be under severe water stress because of high water withdrawals compared to the water availability, and that in over half of the world river basin areas water withdrawals will grow due to population and economic growth leading to rising demand for water, which outweigh assumed improvement in water-use efficiency.
type of study: Impact projection models(s): WaterGAP 2
1. The current global water situation
• The WaterGAP 2 model applied to the current global water situation showed that in about 24 % of the world river basin area the water withdrawal to availability ratio is greater than 0.4, which is considered by some experts as an indication of ''severe water stress''. • The resulting impacts are expected to be stronger in developing countries than in industrialized ones.
2. Future global water situation
• In about 41 % of world river basin area, water withdrawals are expected to stabilize or decrease up to 2025 under a ''business-as-usual'' scenario of demographic, economic and technological trends because of the saturation of water needs and improvement in water-use efficiency. • Elsewhere, withdrawals are expected to increase because of rising water demand due to population and economic growth, which outweigh assumed improvement in water-use efficiency.
3. Uncertainty of computed estimates
• The uncertainty of the computed results is likely to have a strong geographical variability.
 "It is likely that, due to both climate change and increasing water withdrawals, the river-basin area affected by severe water stress (withdrawal : availability >0.40) will increase and lead to increasing competition for available water resources (Alcamo et al., 2003; Schroter et al., 2005)."
quoted from IPCC AR4 II, p.550
Key future impacts and vulnerabilities Water resources
© 2009 ADAM, Adaptation and Mitigation Strategies: Supporting European climate policy